Talk:Metalloid/Archive 30

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Bismuth

There's some dispute about whether bismuth belongs on this page. I'm pretty convinced it does. I think part of the problem is that these are not hard and fast categories, but to some extent a matter of opinion. So it is possible for bismuth to be a poor metal, a heavy metal, and a semimetal.

From G. Jezequel, J Thomas, I Pollini. "Experimental band structure of semimetal bismuth." Physical Review B. 56. 6620 (1997):

The electronic properties of Bi, like those of the group-V semimetals, such as As and Sb, have been for a long time the center of the center of interest of many theoretical and experimenta investigations. Bismuth is a prototype semimetal..."

From J. Heremans et al. "Bismuth nanowire arrays: Synthesis and galvanomagnetic properties" Physical Review B. 61. 2921 (2000):

The galvanomagnetic transport properties of nanowires of the semimetal Bi...

From V. Edelman. "Electrons in Bismuth". Advances in Physics. 25. 555 (1976):

Studies of the electronic properties of bismuth are of interest, first, per se because of the intermediate position of bismuth between ordinary metals and semiconductors.

From an electrical standpoint, bismuth is very different from ordinary metals. So you can see why I feel it should be included in this section. eaolson 03:32, 11 March 2006 (UTC)

How about:

"Bismuth (Bi) also has some metalloid properties."

It definitely has some metalloid properties, and is in about the right place on the Table for a metalloid, but has some properties that may not be expected of a metalloid as well. CaptainVindaloo 00:32, 21 March 2006 (UTC)

There is even more problematic article:

http://www.researchgate.net/publication/13282936_Semimetal-to-semiconductor_transition_in_bismuth_thin_films

Quote: By studying the minority electron concentration as a function of temperature in the range 100-300 K, we have unambiguously confirmed the long-standing theoretical prediction that quantum confinement should convert Bi from a semimetal to a semiconductor at a critical thickness on the order of 300 Å.

Bismuth can be less metallic than astatine, which probably has metal band structure. Can fully metallic (not semimetallic) bismuth exist at ambient conditions? Or it only can have structure of a semimetal (or even be semiconductor in very thin films) at normal pressure? If yes it is a periodic anomaly. What about polonium? It is a metal or a semimetal?

There is another meaning for semi-metal, not equivalent to metalloid

In physics, a semi-metal is a material in which the density of states is zero at the Fermi level. Graphene is an example; the metalloids are not. The "Semi-metal" entry should be reinstated and reference this entry -- it should not be redirected to this entry, as it is now. Does anyone know how to undo a redirection? —The preceding unsigned comment was added by 70.231.194.19 (talk • contribs) .

When you use the redirect page (ie, you search for Semi-metal and get redirected to Metalloid) there will be a link at the top of the page saying "Redirected from Semi-metal". Follow the link back to the redirect page, which you can edit as a normal article. See Wikipedia:Redirect. CaptainVindaloo ^{t c e} 16:12, 7 June 2006 (UTC)

Semimetal vs. metalloid

I've been doing some research, and it seems to me that "metalloid" is used primary in the chemical sense and "semimetal" is used primarily in the electrical sense. I think metalloid is a more general term, referring to materials partway between metals and nonmetals, and semimetal has a more specific meaning, generally referring to something partway between a metal and a semiconductor. The best, most explicit definition I've found is from Burns's Solid State Physics, but unfortunately, there's no online version.

I've created a draft of a new article for semimetal, and would appreciate comments. I'll probably move this over to the actual semimetal article in a few days. eaolson 16:14, 11 June 2006 (UTC)

Ah! I realise why there is much ado about Bismuth now! Some people are looking at this as Chemists, others as Physicists. Chaos results.

The draft looks pretty good. Is there any way it could be illustrated, maybe? Diagrams? Are there any extensive listings of Semi-metal materials at all? Also, it might be an idea to add a notice to make sure anyone looking up either Metalloid or Semi-metal is getting the correct article (eg, getting the Chemical article when they want the Physical article). CaptainVindaloo ^{t c e} 17:31, 11 June 2006 (UTC)

I've added my draft article at semimetal and changed the "semi-metal" redirect. eaolson 00:27, 14 June 2006 (UTC)

"Metalloids" according to the American Chemical Society

Check out the periodic table ACS provides at [1]. I don't know what the original source of their data is, but they give B, Si, Ge, As, Sb, Te, Po as metalloids, Be, Al, Ga, Sn, Bi as metals, and C, P, Se, I, At as nonmetals. Uuh has no designation; after Lr, they stop labelling the element as a metal/nonmetal (they stop specifying it as a solid/liquid/gas after Sg). youngvalter 02:21, 12 November 2006 (UTC)

I have edited the article to make it plain that "metalloid" is not a rigorous term, but just a useful general one for elements which show properties intermediate between "metals" and "non-metals", and that some allotropes of an element may be more metalloid than others. All these squabbles about whether bismuth is this or polonium is that are moot and just terminology quibbles.--feline1 11:22, 15 January 2007 (UTC)

Three undiscovered elements could be considered metalloids

Are elements 167, 168, and 218 are considered metalloids. I knew that element 117 is a metalloid [formerly a metal] while astatine is a nonmetal [formerly a metalloid], and aluminum is a metal even if placed next to a series with single metalloid by looking at the metals and non-metals periodic table. Group 3A is the only group that has just one metalloid--boron and just below it, a metallic aluminum, but boron is bordered at the top of the block. It is hard to predict if these elements should be considered metalloids by following periodic trends from top-left to bottom-right [staircase] of the p-block. Cosmium 03:24, 18 February 2007 (UTC)

The question is a bit pointless, as these elements don't exist - we've never found them in nature, no-one's yet ever managed to make them in a laboratory. So we could only speculate what they might be like, if they ever could be made. There's probably more chance of me winning the lottery than element 218 being discovered! :)--feline1 17:21, 19 February 2007 (UTC)

Just a small question

This article is practically a word-for-word reproduction of the first half of this article. The only thing I'm wondering is: who's copied who? Joelster (talk) 04:48, 9 April 2008 (UTC)

As the guy who wrote most of the sentences in the wikipedia article, I can tell you that "chemical-universe.com" copied wikipedia (in fact, mostly copied ME). B*stards.--feline1 (talk) 13:54, 9 April 2008 (UTC)

[edit conflict] It worried me at first, but after reviewing this article's history, I think we were here first, and they're WP:MIRRORing us. Take for example, the vaguely familiar first and second revisions (diff) from way back in 2002. A later revision in from 2004 (diff) again just looks like iterative progress, and looks very much like what we have today (diff), for instance in the use of the Greek translations. The same thing appears to have happened with Alkali metal[2]. Obviously, a few more eyes on this would be a good idea rather than relying on my opinion alone, but I don't think there's a need for panic here. Not too great on the GFDL front on their part, but it's not the end of the world. CaptainVindaloo ^{t c e} 14:15, 9 April 2008 (UTC)

Yeah, thanks for answering that. Man, they could at least put it in their own words! The website article on metalloids also seems to have copied (seems like another copy-and-paste job) the bullet-point summary from this article on about.com. Joelster (talk) 21:38, 9 April 2008 (UTC)

Someone should probably send a GFDL non-compliance letter, or drop a note at WP:AN. This kind of thing gives me the fear. CaptainVindaloo ^{t c e} 20:51, 10 April 2008 (UTC)

Include Polonium and removed Astatine

As it seems to be. --Feministo (talk) 03:25, 25 August 2008 (UTC)

What is the stairstep line called?

Ok, so that line that is surrounding by metalliods is normally called the stairstep line. What is it really called? —Preceding unsigned comment added by Lrn121 (talk • contribs) 23:20, 6 November 2007 (UTC)

Try asking at WP:RD/S. Personally, I've only ever heard 'stairstep' used. CaptainVindaloo ^{t c e} 17:14, 7 November 2007 (UTC)

Its called an amphoteric line--76.234.102.194 (talk) 23:15, 13 October 2008 (UTC)

Period 6 confusion

There appears to be some confusion along the Period 6 elements, as to whether they are metalloids or not—particularly polonium and astatine. Looking around the web, I see conflicting classifications of elements as metalloids:

Polonium included

• WP article for Polonium (with this ref), as well, most figures and content on Wikipedia (look around, you'll see the shading on Po)
• about.com ("Polonium is often considered a metalloid, too")

Astatine included

• Lecture notes for Chemistry course
• UCAR "Windows to the Universe" education website

Both Po and At are included

• Yahoo! Answers: Metalloids?
• http://chemical-elements.info/
• The Chemistry of Nonmetals
• Encyclopedia Britannica "...sometimes included"

Neither are metalloids

• Yahoo! Answers: Scientifically, are Polonium (Po) and Astatine (At) metalloids?
• Polonium and Astatine are not Metalloids

After digging into this issue, I'm possibly more confused. Could anyone with a good chemistry background offer some incite? +mt 05:37, 8 April 2009 (UTC)

Constant slow edit warring

Considering the rate at which the list of metalloids is changed back and forth, wouldn't it be better to just mark some of them as 'disputed' or 'occasionally considered metalloids'? CaptainVindaloo ^{t c e} 11:52, 20 November 2009 (UTC)

Proposed splits

In response to review feedback, and as way of trimming article length, I propose to hive off the following sections into their own daughter articles:

• 4 Comparison of properties with those of metals and nonmetals
• 6.2 Origin and usage

New article titles will probably be

• Metalloid (properties compared with those of metals and nonmetals)
• Metalloid (nomenclature origin and usage)

Barring any strong views to the contrary I'll do this shortly, in a couple of days or so. I'll leave section summaries in both cases e.g. section 4 will probably list just five each of the most commonly associated physical and chemical properties of metalloids. Sandbh (talk) 00:42, 5 May 2012 (UTC)

GA Review

This review is transcluded from Talk:Metalloid/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: Pyrotec (talk · contribs) 19:52, 26 July 2012 (UTC)

I will review. Pyrotec (talk) 19:52, 26 July 2012 (UTC)

Initial comments

I've done a couple of quick reads of the article. Overall, its certainly well referenced, so it should make GA by the end of this review.

I do think that one or two sections/subsections are a bit "weak", and that includes the WP:Lead - and I don't at this stage believe that the lead is compliant. However, that is all I'm doing tonight, I'll start the review proper tomorrow, starting at Definition. The lead will be done after I've got to the end of the article. Pyrotec (talk) 21:07, 27 July 2012 (UTC)

• Definition

• Looks OK.

• Elements commonly recognized as metalloids -

• I don't regard this sentence: Consistent with the list of metalloid lists, boron, silicon, germanium, arsenic, antimony and tellurium are commonly classified as metalloids.[4][5][19][20][21][22][n 3], as being particularly encyclopaedic. The article list of metalloid lists was created on 15 July 2011 and it is being claimed that books written in 1982, 2001, 1962, 1966, etc, are consistent with it. Well perhaps, but since neither wikipedia nor the article existed in 1962 the authors of that book could not have copied it. The rest of the paragraph makes further claims about some elements being sometimes in the list or sometime excluded. I believe that some elements may or may not be regarded as being metalloids, but whether or not they are listed in list of metalloid lists appears to be somewhat irrelevant - listing by wikipedia does not define them as metalloids.

 Done Actually, list of metalloid lists lists various authors', both pre- and post-Wikipedia, lists of metalloids. The list is copied from the books and not the other way round. Nevertheless, the sentence doesn't seem good to me either, so I've removed "consistent with the list of metalloid lists". I've also removed the bolding for the individual elements, per MOS:BOLD. Double sharp (talk) 08:14, 6 August 2012 (UTC)

Thanks. A "nice and easy change", that I consider has improved the article. Pyrotec (talk) 18:27, 7 August 2012 (UTC)

• • Boron -

• Looks OK.

• • Silicon -

• Generally, OK. The first paragraph mentions that silicon is generally unreactive and is attacked by nitric acid and hot alkalis (well yes), but it does not mention attack by hydrofluoric acid and ignition when hot in chlorine and fluorine.

I can't now remember how I decided to treat these other forms of attack. I seem to recall the intended approach was to more or less address only the standard forms: air; acid (sulfuric; hydrochloric; nitric) and alkali since these were supposed to be summary bio's rather than duplications of main articles. I'll have another look at this re consistency. I see I've also referred to the attack of boron by fluorine, thereby contradicting myself. So, yes, need to go over this again.

Yes, boron has attack by fluorine and antimony has attack by aqua regia. As per my comment below, if the intention is to restrict the discussion to a limited range of "weathering agents", that needs to be stated at the start of the section. Pyrotec (talk) 18:32, 8 August 2012 (UTC)

 Done I've clarified the susceptibility of silicon to various forms of attack. I haven't said anything about reactions at elevated temperatures (apart from e.g. exposure to hot acids) since a. probably most elements will react to something if heated enough, so where do you stop; b. the focus of the bio is supposed to be at ambient conditions; and c. other reactions are more properly the purview of the actual article for the element Sandbh (talk) 00:16, 11 August 2012 (UTC)

• I'm undecided whether this should go here or later in Typical applications. There are a few "obvious" applications that aren't mentioned: silicon carbides, used as abrasives (e.g. carborundum, etc). SiO2 used as silica gel for moisture absorbing, "natural SiO2" in the form of china clay, clay/mud, etc, used for bricks, tiles, pottery; and silicones (used in oils, polymers, etc).

I believe the intention was to only list the uses shared by all of the recognized metalloids, rather their individual-specific uses, as covered in their main articles.

The article could be written in that way, but the wording currently used is: This section includes brief sketches of the physical and chemical properties of the applicable elements. For complete profiles, including occurrence, production, history, biological role and precautions, see the main article for each element. The wording would need to reflect such a decision. Pyrotec (talk) 18:32, 8 August 2012 (UTC)

 Done I've tuned the introductory note to this section in order to (hopefully) better define its scope Sandbh (talk) 11:42, 10 August 2012 (UTC)

• • Germanium -

• Looks OK.

• • Arsenic , Antimony & Tellurium-

• The Arsenic subsection starts off boldly: "Arsenic is a grey, metallic looking solid.". Well the grey allotrope is, but the main article lists two other forms and they are not grey, metallic looking solids. So, it aught to be made clear that this discussion is about the "common" grey form of arsenic.

I'll see if I can make it clearer that the article is about the applicable elements in their most thermodynamically stable forms at room temp, unless indicated otherwise.

 Done Hopefully fixed via another qualifying edit to the introductory note to this particular section Sandbh (talk) 12:22, 10 August 2012 (UTC)

• Antimony also has its allotropes, but they are less stable, so perhaps a clarifying comment is unnecessary.

 Done As per above Sandbh (talk) 12:22, 10 August 2012 (UTC)

• Otherwise, all three subsections are OK.

• • Typical applications -

• See comments above in Silicon.

.... Stopping at this point. To be continued. Pyrotec (talk) 20:50, 7 August 2012 (UTC)

Thank you very much for doing this GA review. Sandbh (talk) 09:00, 8 August 2012 (UTC)

Thanks. I would expect this article to make GA by the end of the review, these a just "minor problems" that need to be sorted out first. Pyrotec (talk) 18:48, 8 August 2012 (UTC)

• In general, I have no problems with this subsection. However, I would have been tempted to suggest the borax article as source of additional information on other uses of boron which don't appear here; but that will be dependant on resolving the comments raised in Silicon, above. Pyrotec (talk) 18:48, 8 August 2012 (UTC)

 Done As per edit (for silicon) to the introductory note to this particular section Sandbh (talk) 12:22, 10 August 2012 (UTC)

• Elements less commonly recognized as metalloids -
  • Untitled subsection -

• Looks OK.

• • Carbon -

• I found the claim: It can form ionic salts, including a sulphate, perchlorate, nitrate, hydrogen selenate, and hydrogen phosphate.[228] some what surprising, but ref 228 did give an example of the formation of C⁺₂₄H₂SO₄^-.2.4H₂SO₄ and states that other salts can be formed. They are, according to the source, rapidly attacked by water and by moisture in the air. However, I do not think that the statement can stand as it is without further explanation. The method of preparation is (careful) direct oxidation of graphite in concentrated sulphuric acid by oxidising agent, so the concentrated sulphuric acid is acting as an Inorganic nonaqueous solvent.

 Done I've incorporated your good prose into a note. Sandbh (talk) 11:07, 15 August 2012 (UTC)

• • Aluminium -

• It states: Its oxide is amphoteric, and a conditional glass-former.[62], well the reference only confirms that it is a glass-former. Aluminium oxide is quite unreactive, its certainly less chemically reactive than the metal and it has a higher melting point. I'd suggest that Aluminium, itself, is amphoteric as it forms aluminates (and that is stated in Other metalloids).

 Done I've added a reference re the amphoterism of the oxide. I steered away from mentioning the amphoterism of actual elements, as opposed to their oxides, in order to avoid confusion with the other concept of metalloids as amphoteric metals, such as vanadium, chromium, molybdenum, tungsten, and lead. Sandbh (talk) 11:07, 15 August 2012 (UTC)

• • Selenium & Polonium -

• Both subsections look OK.

• • Other metalloids, Near metalloids & Allotropes -

• This three subsections look OK.

• Categorization and periodic table territory -

• Looks OK.

• Comparison of properties with those of metals and nonmetals -

• Looks OK.

• Quantitative description & Nomenclature and history -

• These two sections look OK.

• WP:Lead -

• This is intended to both introduce the topic and summarise the main points (see WP:Lead. For an article of this length, this lead is rather "thin", but three (or four) paragraphs is an adequate number. The lead is also required to proportionately cover all the points in the article; and the section that appears to be entirely absent is Elements less commonly recognized as metalloids, which forms perhaps a third to a quarter of the article (excluding the notes and citations).

At this point, I'm putting the review On hold, the article is substantially compliant apart the lead which needs to be brought up to standard. Pyrotec (talk)

 Done Thank you Pyrotec. I've added a paragraph summarizing the nub of the Elements less commonly recognized as metalloids section. It borrows some of the periodic table territory part of the following section, since the two notions are closely related. Sandbh (talk) 11:35, 16 August 2012 (UTC)

Thanks. 18:31, 16 August 2012 (UTC)

Overall summary

GA review – see WP:WIAGA for criteria

---

An informative and well referenced article

1. Is it reasonably well written?

   A. Prose quality:

   B. MoS compliance for lead, layout, words to watch, fiction, and lists:

2. Is it factually accurate and verifiable?

   A. References to sources:

   B. Citation of reliable sources where necessary:

   C. No original research:

3. Is it broad in its coverage?

   A. Major aspects:

   B. Focused:

4. Is it neutral?

   Fair representation without bias:

5. Is it stable?

   No edit wars, etc:

6. Does it contain images to illustrate the topic?

   A. Images are tagged with their copyright status, and valid fair use rationales are provided for non-free content:

   B. Images are provided where possible and appropriate, with suitable captions:

7. Overall:

   Pass or Fail:

I'm happy to award this article GA-status. Thanks for responding quickly and positively to my comments above. Pyrotec (talk) 18:31, 16 August 2012 (UTC)

Generic definition at start of article

I restored the generic definition of metalloid from…

A metalloid is a chemical element with properties that are in-between metals and non-metals, or have mixed characteristics. Metalloids are thus considered to be difficult to classify as either a metal or a nonmetal.

…back to its original form:

A metalloid is a chemical element with properties that are in-between or a mixture of those of metals and nonmetals, and which is considered to be difficult to classify unambiguously as either a metal or a nonmetal.

Reasons:

1. The first definition would imply that gold, which has a mixture of metallic and nonmetallic properties, is a metalloid. See note 2 of the Metalloid article for more about this. As also noted in the Definitions section of the metalloid article, 'most other elements [also] have a mixture of metallic and nonmetallic properties' thereby compounding the problem.
2. It is not completely clear what the expression 'mixed characteristics' in the first definition is referring to. It seems to be saying that the properties of a metalloid have mixed characteristics however a property is just a property: most properties do not have mixed characteristics or rather, saying that a property has mixed characteristics, rather than a metalloid has mixed properties, is confusing.
3. The first definition is not sufficiently anchored in the Definitions section of the Metalloid article, which notes that, 'The generic definition set out at the start of this article is based on metalloid attributes consistently cited in the literature.' and then gives illustrative examples.
4. The first definition has removed 'unambigously' from the end of the phrase, 'difficult to classify'. As noted in the Definition section of the Metalloid article, 'The criterion that metalloids are difficult to unambiguously classify one way or the other is a key tenet.' The 'unambiguously' qualifier was also supported by other references in an earlier metalloid definition dated 05:48, 19 May 2012: 'A metalloid is a chemical element with properties that are in-between (Deming & Hendricks 1942, p. 170) or a mixture (Butler 1930, p. 23) of those of metals and nonmetals, and which is considered to be difficult to classify unambiguously (King 1979, p. 13) as either a metal or a nonmetal (International Textbook Company 1908 p. 21; Hill & Holman 2000, p. 41).' These citations were removed as part of preparing the article for a GA review.

• Butler JAV 1930, The chemical elements and their compounds: An introduction to the study of inorganic chemistry from modern standpoints, Macmillan, London
• Deming HG & Hendricks BC 1942, Introductory college chemistry: a course for beginners, John Wiley & Sons, New York
• Hill G & Holman J 2000, Chemistry in context, 5th ed., Nelson Thornes, Cheltenham, ISBN 0-17-448307-4
• International Textbook Company 1908, International library of technology: a series of textbooks for persons engaged in the engineering professions and trades, or for those who desire information concerning them, vol. 6, part 2, ITC, Scranton, PA
• King EL 1979, Chemistry, Painter Hopkins, Sausalito, Calif., ISBN 0-05-250726-2

Sandbh (talk) 06:46, 17 October 2012 (UTC)

Properties of metalloids

While this article is very comprehensive and awesome, I found that one noticeable exclusion was a section on properties of elements metalloids. Whilst gong into definitions, the various elements which are always/sometimes included, and uses, the information I wanted to read most was oddly missing. This website gives an example of the sort of thing the section would include. While there are some quotes like "he reactivity of the metalloids depends on the element with which they are reacting." and "the boiling points, melting points, and densities of the metalloids vary widely", the fact that they vary considerably is as notable than if there was a common thread here. But there are still some some common properties such as "they tend to make good semiconductors". My question is essentially: can this section get written?--Coin945 (talk) 12:37, 2 February 2013 (UTC)

At the moment the properties of metalloids are summarized in the second paragraph of the lead, and section 5 Comparison of properties with those of metals and nonmetals. I can see your point however. I'll see if I can put a Properties of metalloids section between section 1 Definitions, and section 2 Elements commonly recognized as metalloids. Want to try and avoid duplication, as much as possible. Sandbh (talk) 22:19, 2 February 2013 (UTC)

Thinking about something like this (have left out citations):

Properties

Ordinarily, metalloids are metallic-looking brittle solids with intermediate to relatively good electrical conductivities. At the atomic scale, they have relatively open crystal structures, with medium coordination numbers, in contrast to the close-packed crystal structures of most of the metals. At the electronic scale each has the electronic band structure of a semimetal or semiconductor. Chemically they generally behave as (weak) nonmetals, have intermediate ionization energies and electronegativity values, and have amphoteric or weakly acidic oxides. They can, however, also form alloys with metals. Most of the other physical and chemical properties of metalloids, which are set out in Metalloid (comparison of properties with those of metals and nonmetals), are intermediate in nature.

Brittleness or semiconductivity or both have been cited or used as distinguishing indicators of metalloid status. Metallic lustre together with very marked dualistic chemical behaviour—by way of, for example, amphoteric oxides—has also been cited as a benchmark.

Although metalloids are all reckoned to be solid and have metallic lustre, their other properties are said to vary. Given metallic character (for example) is a combination of several properties, it has been suggested that metalloid status be judged separately for each element. This could be done based on the extent to which an element exhibits properties relevant to such status.

If I did this, it would become section 2 and the current section 5 Comparison of properties with those of metals and nonmetals would disappear. Sandbh (talk) 12:37, 8 February 2013 (UTC)

Thankyou for taking the time to investigate this matter. Yes, I do think that such a section (even if it included merely a rearranging of the information from the two aformentioned sections), would be a very handy inclusion. "properties of metalloids" is a much more succinct heading, and it opens up the possibility for "Comparison of properties with those of metals and nonmetals" to be a subsection. I just concede, after examining the article in greater depth, that the information i was looking for was indeed there, but was perhaps a bit obscured by the many subheadings and comprehensively written text. If you did make the alterations you describe, I think it would be a valued contribution to the article. I think there is merit in both a prose explanation, and a visual representation in the form of a table. Perhaps they can both be implemented in the new section.--Coin945 (talk) 13:22, 8 February 2013 (UTC)

This is very good, Coin945. I've done some more work on your suggestions and now have a draft section with the following structure:

2. Properties of metalloids

2.1 Physical and chemical

2.2 Distinctive

2.3 Compared to those of metals and nonmetals.

Please see my sandbox, and let me know how it looks to you (I like it a lot). Sandbh (talk) 07:55, 9 February 2013 (UTC)

I love it! Concise and well written. Perhaps a bit more explanation needs to be given about the three subsections. I first thought that "Distinctive" and "Compared to those of metals and nonmetals" were subsets of "Physical and chemical"... but now I'm not sure. One other thing. May I suggest pipelinking the first Metalloid (comparison of properties with those of metals and nonmetals)? It's just that having it in the middle of a sentence is a bit jarring, and you have the exact same link two paragraphs below. Maybe something like: "Most of the other physical and chemical properties of metalloids are intermediate in nature". Besides that, magnifique. :D--Coin945 (talk) 14:16, 9 February 2013 (UTC)

OK, that's great, thank you! Pipelinking done. I toyed around with adding an intro to the section. Decided against it---starting to get too much duplication. If there are issues with section structure try and fix these. Have added 'Of the above properties…' to the front of the 'Distinctive' subsection to make its relationship to the 'Physical and chemical' subsection clearer. Also changed the order of the opening of the 'Compared to those of metals and nonmetals' subsection, to better distinguish this as a discrete subsection. And added a concluding paragraph after the table. Oh and I moved the old draft to the end of the sandbox. Sandbh (talk) 02:17, 10 February 2013 (UTC)

Well, I went ahead and did it. Hope it looks OK. Sandbh (talk) 06:43, 10 February 2013 (UTC)

English language variety

The question of which English variety this article should be written in has been posted here Sandbh (talk) 01:01, 17 February 2013 (UTC)

Use of the hyphenated word 'in-between' in the generic definition

I restored the generic definition of metalloid from…

A metalloid is a chemical element with properties that are between, or a mixture of, those of metals and nonmetals, and which is considered to be difficult to classify unambiguously as either a metal or a nonmetal.

…back to its original form:

A metalloid is a chemical element with properties that are in-between or a mixture of those of metals and nonmetals, and which is considered to be difficult to classify unambiguously as either a metal or a nonmetal.

The hyphenated word 'in-between' was taken from Deming & Hendricks (1942, p. 170), who wrote that, 'A metalloid is a chemical element with properties that are in-between…'.

Use of 'in-between' is also supported by examples such as:

1. 'Adolescence is an awkward, in-between age.'
2. 'The switch is either on or off; there's no in-between.'
3. 'available in small, large, and in-between sizes'
4. 'a coat for in-between weather.'
5. 'he's at the in-between stage, neither a child nor an adult'
6. 'Boron is an in-between element.'

The first five examples are from:

• The American Heritage Dictionary of the English Language, 5th ed., 2011;
• Merriam-Webster's Learner's Dictionary, 2008;
• Dictionary.com Unabridged, based on the Random House Dictionary (2013); and
• Collins English Dictionary, 10th Edition (2009).

Example number 6 is from Parry et al. 1975, Chemistry: experimental foundations, 2nd ed., Prentice Hall, p. 449

Reference
Deming HG & Hendricks BC 1942, Introductory college chemistry: a course for beginners, John Wiley & Sons, New York

I can see you've put a lot of effort into tracking down instances of "in between" being hyphenated, but unfortunately you haven't understood the grammar behind it. English compound#Hyphenated compound modifiers might be helpful. Basically, when a set of words acts an adjective, it is most often often hyphenated. You can see this in the examples you provided: in #1, "in-between" modifies the noun "age; in #6, "in-between" modifies the noun "element". In the lead to Metalloid, however, "in between" isn't working as an adjective, but as a preposition (as it normally does), in which case it takes no hyphen: "in between A and B". An easy way to test which is which is to try slapping an article ("a" or "the") in front of it. Can you say "the in between A and B"? No? Then don't hyphenate. Can you say "the in-between place"? Yes? Then hyphenate. Curly Turkey (gobble) 21:25, 12 March 2013 (UTC)

Would this mean that the following sentence (which is a little contrived) would be grammatically correct(?): 'Boron, which has in-between properties, is a metalloid, a class of elements with properties that are in between or a mixture of those of metals and nonmetals.' I gather the first use of 'in-between' is as an adjective, hence hyphenated, whereas the second use (i.e. 'in between') is a preposition, hence unhyphenated? Sandbh (talk) 22:51, 16 March 2013 (UTC)

Yes, that's right. Curly Turkey (gobble) 23:55, 16 March 2013 (UTC)

Crushing weight of semantic clarification

I can't believe how much page space this article devotes to what or what isn't a metalloid. There's not enough payoff for reading all that, and it discourages readers. As a semantic issue, it's not that crucial. No one is disputing any chemical properties, just how to classify. It's minutiae that can be summed up in a single paragraph.

I now click 'save page', hoping someone will.

173.25.54.191 (talk) 03:08, 18 April 2013 (UTC)

Thank you for taking the time to record your well-crafted feedback. One paragraph descriptions of what is (and, by implication, what isn't) a metalloid are "a dime a dozen" so I'm not sure what purpose would be served by another one of these. The actual amount of space taken up on this question is relatively small and seems about right for an article of this size. The importance of metalloids to society, noting the exploitation of their properties enable modern telecommunications (and the internet), arguably warrants more than a one paragraph description of what is or isn't a metalloid. Statements in the chemistry literature attempting to addressing this question go back nearly one hundred and fifty years, and overlap into the fields of classification science and, more recently, fuzzy logic. Discrepancies occur even within the field of chemistry, where selenium is generally not regarded as a metalloid within inorganic chemistry but is more commonly so regarded within environmental chemistry. In light of all of the preceding, and noting there is no agreed definition of what is metalloid, I think the amount of space devoted to this (difficult) question is proportionate. It is certainly succinctly addressed in the lead, and that may be enough for some people. Whereas people such as myself will (or may) appreciate a more nuanced explanation. Sandbh (talk) 04:40, 25 April 2013 (UTC)

Trendbreakers

Hydrogen and helium should be metalloids due to they electronic configuration (hydrogen maybe even a metal). They are in 1 period and one or two valence electrons. Beryllium (metal) and boron (metalloid) are in 2 period. Be has 2 valence electrons, B has three. In third period Al (metal) has 3 valence electrons, Si (metalloid) - four. In fourth period Ge has 4 valence electrons (metalloid or metal), As has five (metalloid). In fifth Sb has 5 valence electrons (metalloid or metal), Te has 6 (metalloid). In sixth period Po has 6 valence electrons (metal), At has seven (due to the trend it should be a metalloid, but is probably a metal and next "trendbreaker" after H and He). What about elements 117 and 118? Can element 118 be metalloid or metal?

About metallicity of astatine:

http://www.rsc.org/chemistryworld/2013/09/astatine-metallic-superconductor-predictions

If that ever happens, new first-principles calculations published in Physical Review Letters predict that it will be a metallic solid. That’s perhaps not so surprising given that iodine, the halogen above it in the periodic table, is itself a dark silvery solid (although not truly metallic itself) and that astatine’s melting point is 302oC. But the real surprise of the new results is that the solid wouldn’t be composed of diatomic molecules, like all the other halogens, but would be monatomic. The calculations were performed by Andreas Hermann, now at the University of Edinburgh in Scotland, and veteran theorists Roald Hoffmann and Neil Ashcroft of Cornell University in Ithaca, New York.

Theoretical physicist Yanming Ma of Jilin University in Changchun, China, who has worked on high-pressure solid phases of the other halogens, calls this ‘a wonderful paper.’ ‘The authors present convincing evidence of this surprising behavior of solid astatine,’ he says, adding that the surprise is twofold: ‘its non-molecular form and its metallicity at ambient pressure.’

This behaviour would be easy to miss, because it only manifests when the calculations take full account of the effects of special relativity on the electronic structure of the very heavy atoms: the increase in effective mass of fast-moving electrons close to the massive nucleus. Such effects are known to have significant consequences for heavy elements, famously giving gold its yellow tint and mercury its low melting point.

Importance of spin orbit coupling

In density-functional calculations of the electronic structure of molecules and materials, relativistic effects are commonly split into two components. The so-called scalar approximation considers just the effects of the electrons’ very high speed, whereas their energy is also affected by spin-orbit coupling between the electron spin and the magnetic field created by electron motions around the nucleus. Hermann and colleagues found that a scalar-relativistic calculation predicted a diatomic ground state for astatine, whereas the monatomic form appeared only with spin-orbit coupling included. ‘These effects influence the atoms’ propensity to form certain bonds and crystal structures, usually by reducing molecular binding energies,’ says Hermann. Earlier calculations have indicated that in the gas phase astatine would still form a weakly bound diatomic molecule.

The fully relativistic solid state has no band gap between the valence and conduction electrons: it is a metal even at ambient pressure. In fact, by analogy with high-pressure iodine, the researchers say astatine might even be a superconductor.

79.191.197.55 (talk) 13:40, 1 November 2013 (UTC)

Metallicity of elements

Course of differnece of metal charcter between C, P and Se is interesting. I think that there are some misleading stereotypes. P is less nonmetallic than it is popularily thought, especially in its black allotropes. Se is also an interesting element beause of its grey allotrope. Graphite, black P and grey Se are metalloids rather than nonmetals.

From other discussion: "black P apparently sublimes at 394º C". Why it is written that it has melting point about 610 C? 394 C = 667 K. Phosphorus has atomic mass 31 u. Arsenic has 75 u, but it sublimation point / atomic mass qoutient is lower than the same quotient for black phosphorus. Sublimation point of grey arsenic is about 887 K, only about 220 K higher than 394 C. As and P have almost the same electronegativities. Is yellow arsenic more volatile than grey? I think that it even should not be, because white phosphorus has boiling point about 280 C (553 K). Yellow As should have it about 1335 K, far much less than sublimation point of grey form of As. Does violet P sublime at 620 C? It is qutite high temperature. In addition, violet form is less metallic than black.

S (32,06 u, Bp 717.8 K) and Se (78,971u, Bp 958 K) have quite wide liquid range for nonmetals. It is especially interesting in S, which is quite significantly nonmetallic light element. Iodine and sulfur - it is interensting. Iodine belongs to carbon diagonal, sulfur to nitrogen diagonal. Therefore iodine should be more metallic. It is heavier (Z = 53) than C, P and Se, but less metallic than they.

194.29.130.244 (talk) 07:51, 29 October 2013 (UTC)

My reference for black P subliming at 394 C was Yu Tonkov (1992, p. 630). However Wiberg (2001, p. 682) says black P is only stable up to 550 C at which point it is converted to violet P, which sublimes at 620 C, or melts at a pressure of about 4.9 MPa.

• Wiberg N, Holleman AF & Wiberg E (eds) 2001, Inorganic chemistry, Academic Press, San Diego.
• Yu Tonkov E 1992, High pressure phase transformations: A handbook, Gordon and Breach, Philadelphia.

Diamond is not so nonmetallic. It only has wide band gap, which makes it colorless and insulating (gives some typically nonmetllic properties). It is more similar to boron, silicon and germanium. Other properties are often very similar or even better than in typical metalloids (B, Si, Ge). They have high melting and boiling points, hardnesses, thermal conductivities (unlike nonmetals). Diamond is extremely dense when we compare its density and atomic number or molar mass (even denser than all metals). It has higher hardness, melting point and thermal conductivity than all measured metals. It does not pass to nonmetals so well, it better pass to metalloids. Diamond is one of the most unique element forms at ambient conditions. Diamond is not so metallic than Ge, Si, B, but it is also not so much nonmetallic. It is unique example of (semi)metalloidal allotrope. — Preceding unsigned comment added by 79.191.197.55 (talk) 13:50, 1 November 2013 (UTC)

Another interesting question: is Al more metallic than Sn? Al has: 1.Higher melting point 2. Better hardness 3. Better electrical conductivity 5. Better thermal conductivity 6. Lower electronegativity 7. Lower first ionisation energy. 8. Nonvolatile (polymeric) hydride, Sn has very volatile tetrahydride 9. Sn has metalloidal allotrope with band gap about 0,08 eV. 10. Tetrachloride of Sn is monomeric liquid, trichloride of l is dimeric solid. First eight points are also true when Pb and Al are compared. Sn has slighly higher boiling point than Al, Pb has much lower. Aluminium is really metallic. More than Sn, I think. It would be strange because Al belongs to diagonal beryllium group and Sn to diagonal lithium group (Pb even to diagonal sodium group). — Preceding unsigned comment added by 178.42.158.85 (talk) 19:53, 1 November 2013 (UTC)

Strange (and wrong) classification - boron a nonmetal, silicon a "semimetalloid" and selenium a metalloid:

http://www.docbrown.info/page03/3_34ptable.htm#2c.

For me, carbon definately does not pass to typical nonmetalloidal elements (boron, of course, even more). It can't be classified as less metallic than selenium, such as phosphorus, which metallicity is also (even more) "underestimated". Selenium oxides and hydrides are more acidic than carbon and phosphorus ones. Boron is more metallic than selenium, it has high melting point, boiling point, theraml conductivity, hardness, it is far much better conductor at higher temperatures and form metal-like compound with more metallic elements. B and Si are on the typical metalloid diagonal. Silicon is maybe even more metallic than arsenic. Arsenic is toxic and tricky element. It has very metallic main allotrope, but unstable yellow allotrope is very nonmetallic (it is also true for Sb). Trioxide of arsenic (dimer) is very volatile when we compare its molar mass to boiling (sublimation) point. Silicon dioxide is very semimetalloidal substance, Si has lower electronegativity (the lowest of all metalloids). Silicon dioxide is very NONvolatile due to low electronegativity of silicon. Metalloid have rather significally amphoteric oxides, semimetalloid rather only acidic (C, P, Se). Allotropes of semimetalloidal or even metalloidal elements can be transparent and highly insulating. Typical nonmetals does not form large covalent structures, they have only molecular nonmetallic form at normal pressure, have low electrical and thermal conductivities and melting and boiling points. Typical nonmetals easier form anions. They oxides are volatile and highly acidic. Hydrogen oxides and fluorides are even less volatile than oxides and fluorides of typical semimetalloids (C, P, Se) - compare molar masses and boiling (sublimation) points. Hydrogen has atypically low electronegativity for a nonmetal, but its physical appearance is clearly nonmetallic (volatile, diatomic and transparent). H is less metallic than phosphorus, but more than oxygen. Rn, S, I also are more metallic than typical nonmetals, but less than C, P and Se. Graphite in many properties is definately much metallic and metalloidal than grey selenium. Melting, boiling point (huge difference), band gap, electrical (in the darkness at least) and thermal conductivity... Diamond is not so clearly nonmetallic (in my opinion semimetalloidal), it is generally more similar to crystalline forms of B, Si and Ge. Diamond "suffers" because of very wide band gap which makes it insulating and colorless.

Boron and silicon oxides can also reacts with acids, such as oxides of As and Te. B, Si, As, Te are very similar in average metallic properties and can be named as "typical metalloids". Germanium has the same structure as diamond and is even worse electrical condutor than graphite (a "nonmetal" which is in fact highly metalloidal) at normal conditions. Germanium lies on beryllium diagonal, such as Al, Sb, Po. Metallic character of germanium is lowe than of aluminium. Sb is more metallic than Ge (for me) because main allotrope of Sb conducts electricity as a metal. Sb is the most metallic from commonly recognised metalloids.

C, P and Se does not pass to nonmetals so good, they have borderline properties between nonmetal and metalloids. Oxides are still acidic (especially selenium trioxide), but most stable allotropes are metalloidal - grey, shiny, highly conducting and with higher melting point than typical nonmetallic substances. They are the most metallic class of "nonmetals". Second class is more nonmetallic - I, S, H, Rn, electronegativities still low as for a nonmetal, iodine has metallic appearance and sulfur is polyatomic, two gases have electronegativity 2,2 in the Pauling scale, lower than some heavy metals. Other nonmetals are less metallic than they (Xe, Br, N, Kr, Cl, O, F, Ne). Helium has strange properties - it is superfluidal and very, very good theraml conductor at very low temperatures (superfluid). Helium is in first period and has two valence electrons. Difference between number of valence electrons and number of period is 1, such as for B, Si, As, Te and At. Due to this helium should be a metalloid, but it is not a metalloid. It breaks the trend. Hydrogen does the same - it should ba a metal or metalloid, but is nonmetal (weak semimetalloid).

194.29.130.244 (talk) 09:00, 4 November 2013 (UTC)

Persistent error in (not only) German Wikipedia

In German Wikipedia (such as in many other sources) selenium is consequently classified as metalloid, but other elements which have the same general level of metallicity (carbon and phosphorus (which metallicity is not well-known)) are classified only as nonmetals. Carbon has more marked (sometimes even blatantly) breakings of nonmetallic traits (melting and boiling points, hardness and electrical or thermal conductivity) in graphite and (or) diamond. Selenium has stronger acids, such as selenic acid and significantly acidic monohydride. I think that this error should be consequently correcting (selenium is even named as "non-ferrous metal" in English Wikipedia). Less metallic iodine also looks very metallic (quite bright grey solid with metallic luster). Selenium definately better passes do carbon and phosphorus than to boron, silicon, arsenic and tellurium in terms of general level of metallic character.

79.191.195.142 (talk) 17:04, 9 November 2013 (UTC)

Semimetalloids

I think that classified selenium as a metalloid when carbon and phosphorus are classified only as nonmetals is inappropiate and flawless.

Carbon (especially graphite) is really metalloidal substance. Maybe even more than toxic selenium. Selenium has more acidic oxide and hydride than carbon and phosphorus. Carbon is probably often associated with biology, not with severe not-nonmetallic properties (melting point of carbon evidently do not pass to nonmetals, such as condcutivity of graphite), and phosphorus is associated with most nonmetallic white allotrope. Graphite is a metalloid. If grey selenium is classified as metalloid, graphite and black phosphorus have to be also. Many periodic tables are wrong because they mark only metallicity of selenium and omit metalloidal properties of most stable allotropes of C and P.

Diamond is not so nonmetallic. Nonmetals does not have such high melting, boiling or sublimation points. Diamond is similar to aluminium oxide or cubic zirconia (compounds contains metal and nonmetal atoms) more than to any nonmetal.

Elements in diagonal from carbon to iodine are typical semimetalloids. They have less metallic properties than typical metalloids (diagonal boron group), but much more than diagonal nitrogen group. Most stable forms of semimetalloids (graphite, black phosphorus, grey selenium, iodine crystals) have metallic luster and grey color. They looks similar to more metallic elements. Chemically they are also more metallic than elements on the right. They acids are weaker. Iodine is also a semimetalloid, especially due to it metalloidal appearance at ambient conditions.

Some questions:

Is carbon more metallic than selenium? In many characteristics yes (melting point, conductivity at ambient conditions). In some characteristic carbon is more similar to typical metalloids (boron and silicon). Glassy carbon is hard, such as silicon, and is far much better conductor of heat and electricity than nonmetals. It is lso a metlloidal allotrope of carbon. Chemically, carbon is at the same grade of metallicity as phosphorus and selenium (which often is highly similar to sulfur).

Is selenium more metallic than phosphorus? Rather phosphorus is generally more metallic.

Black phosphorus have higher melting point than gray Se and have lesser electronegativity. Oxide of P is less acidic than oxide of Se. Phosphorus hydride is not (so) acidic, contrary to hydrogen selenide. Phosphoric acid has similar properties and acidity to arsenic acid (arsenic is a typical metalloid), but selenic acid is similar to sulfuric acid and has acidity like sulfuric acid (sulfur is more nonmetallic than carbon, phosphorus and is most nonmetallic known solid element). Selenic acid is far much acidic than carbonic, oxalic and phosphoric.

Is carbon more metallic than phosphorus?

Phophorus can be more metallic due to lower electronegativity.

79.191.191.243 (talk) 20:27, 23 October 2013 (UTC)

— Preceding unsigned comment added by 79.191.191.243 (talk) 20:07, 23 October 2013 (UTC) 

I agree with you about C, P (black), Se and I. P is a bit tricky because the standard state is defined as white P rather than black P. While all of these elements have been identified as metalloids in the literature, only for Se are there are a reasonable number of such mentions and even then three times as many authors categorise it as a nonmetal. There are no sources in the literature that I know of that categorise these elements as semimetalloids. The closest there is is 'near metalloid' for C, P and Se. If you have a look at the nonmetal article you will see that C, P, and Se are categorised as polyatomic nonmetals which is the closest we get to the concept of semimetalloids. I is categorised as a diatomic metal but the article notes that it is almost a polyatomic nonmetal. Sandbh (talk) 00:00, 24 October 2013 (UTC)

Iodine is more metallic than sulfur. Sulfur belongs to nitrogen diagonal group, iodine to carbon diagonal group. We can look at pure crystalline iodine and it looks really like a metal, more than like a nonmetal. Sulfur (in ll allotropes) looks far much nonmetallic.

If classification to "polyatomic" and "diatomic" nonmetal is used, the difference in metallicity in iodine and sulfur is not marked appropiately. It can suggest that sulfur is generally more metallic than iodine becuse sulfur is then classified with C, P and Se and iodine with N, O, F, Cl and Br (more typical nonmetals). But that classification is better than (used in example in German Wikipedia) classification in which selenium is classified as metalloid (despite it place in periodic table at carbon diagonal), but P and C are only nonmetals. It can be named as wrong. The differences in metallicity between C, P and Se are so small. Carbon (especially graphite) is too exceptional among nonmetals (melting point, conductive allotropes, appearance of graphite), but is less metallic than typical nonmetals (B, Si, As, Te) from diagonal boron group (which is easy to understnd when we look at periodic table). In metallicity, carbon is definately more similar to it diagonal counterparts, especially P and Se. Oxides of carbon, although gaseous (due to very low atomic mass of carbon and its electronegativity on par with electronegativity of selenium, gaseousness of carbon dioxide is very important for life), are not so soluble in water and not so acidic. Carbon atom is nearly 3 times lighter than phosphorus and about 7,5 times than selenium. Boron trichloride and silicon tetrachloride (heavier) have lower melting and bolinig point than carbon tetracloride, these metalloids are very similar to carbon and nonmetals it this way. In addition, selenium has more acidic oxide and hydride than carbon and phosphorus. Selenium is really similar chemically to sulfur.

95.49.94.63 (talk) 15:21, 24 October 2013 (UTC)

S and I are not that clear. S has a lower electronegativity (Pauling); lower first ionization enthalpy; lower electron affinity; lower standard reduction potential; higher melting point (just); higher boiling point; and a longer liquid range than I. The most stable oxidation state for S is +6 whereas that of I is –1. S has a ductile form; I does not. I, on the other hand looks like a metal, has a higher Goldhammer-Herzfeld metallicity ratio, has a smaller band gap, is a better conductor, and has a lower electronegativity (Allen scale).

It doesn't matter, in any event. Sulfur is a polyatomic nonmetal; iodine is diatomic nonmetal. Each one is the outlier in their category, just as radon, which shows cationic behaviour, is the outlier among the noble gases. The outliers form overlap zones at the edges of each category just as there are overlaps, for example, between lithium and magnesium; beryllium and aluminium; the lanthanides/actinides and the transition metals; the group 11 metals and the poor metals; the poor metals and the metalloids; and the metalloids and the polyatomic nonmetals, as the first IP editor observed.

There is no perfect categorisation scheme, even one as simple as metals, metalloids and nonmetals or simpler yet, just metals and nonmetals. As long as the categories are reasonably coherent, and useful, then a few borderline cases or boundary overlaps won't matter. Given the large variation of properties even within the supposedly homogenous category of metals, overlaps are inevitable and simply a reflection of Mendeleev's observation that metallic properties gradually give way to nonmetallic properties, there being no simple delineation between the two. Personally, I view the overlaps as links that join all of the categories together. To have no overlaps would require too many categories to be meaningful. Either that or show some elements as split categories, such as metalloid/polyatomic nonmetal, a suggestion which was made some years ago and more recently but which never garnered much support. Sandbh (talk) 08:07, 25 October 2013 (UTC)

And what with selenium and phosphorus? Which is more metallic? Difference is not too much. It is quite interesting. It is possible that phosphorus is more metallic than selenium and carbon. Iodine has electronegativity 2.66, sulfur 2.58 (difference 0.07). Phosphrorus has 2.19, C and Se 2.55 (difference 0.36). Black phosphorus has bandgap 0.34 - 0.35 eV (silicon 1.11 eV, germanium 0.64, grey selenium - 1,8 eV). I can not find informations about boiling point of black phosphorus. Melting point of black P is significantly higher (610 C) than melting point of grey Se (221 C). Electron affinities: C 122, P 72, Se 195, I 295 (S 200, H 73, Si 134). Interestingly, selenium has the lowest first ionisation energy of them (but phosphorus have lower second and third than Se). Thermal conductivity of black phosphorus - 12.1 W·m−1·K−1, grey selenium - (2,344 W·m−1·K−1? (http://encyclopedia2.thefreedictionary.com/selenium+sulfide,+selenium+disulfide)), resistance - about 100 Ωcm in the dark (black P - very anisotropic, 0.1, 1 and 100 - 1000 Ωcm), both are very significantly worse than graphite in some classifications (electrical and thermal conductivity, melting and boiling point). Phosphorus looks very slightly better.

Some informations about conductivity of black phosphorus are on this page:

http://www.tandfonline.com/doi/abs/10.1080/00268948208073686#.Umr3ilMjpNM

I think that making difference in metallicity between C, P and Se is wrong (but very popular in the case of Se named as a metalloid). It is even annoying.

79.185.135.200 (talk) 23:43, 25 October 2013 (UTC)

In the case of sulfur and iodine, both elements are normally classified as nonmetals. But selenium is very often classified as metalloid as only element on the diagonal on the right from typical metalloid. Why there is so prejudice? It suggests non-existing difference between C, P and Se. Under sufficiently high pressures, just over half of the nonmetals, starting with phosphorus (not selenium) at 1.7 GPa, have been observed to form metallic allotropes. Carbon behaves very oddly (due to its position in periodic table and electronic configuration) because it "diamondizes" (not metallizes, such as oxygen) at high pressures, which makes it non-conductive (of electricity). At standard conditions (pressure, darkness, temperature), "metallic carbon" (graphite) is far much better conductor of heat and electricity than metallic allotropes of P and C. Boiling point of black phosphorus is really interesting. When graphite is a solid at very high temperature (about 3000 C), selenium is a gas, but black phosphorus? Diamond itself is unique allotrope due to its abnormal hardness, density compared to atomic number or atomic mass, thermal conductivity and remaining solid at hery high temperatures (even above 3500 C at ambient conditions) (these traits are popularily asscociated with... metals). Substances similar to diamond contains metal or metalloid atoms. Diamond is far much less metallic than graphite (because it is insulator, transparent subsatnce with wide bandgap), but still other than typical nonmetallic substances. Carbon looks less metallic than phosphorus due to its high electronegativity at all scales. They are significantly closer to selenium than to phosphorus.

95.49.68.75 (talk) 10:41, 26 October 2013 (UTC)

Some comparison between phosphorus and selenium:

http://chemical-elements.findthedata.org/compare/69-87/Phosphorus-vs-Selenium

Phosphorus - reference to less metallic allotropes is usual. Especially about melting and boiling point. Crbon and phosphorus seems to be more tricky than selenium.

95.49.68.75 (talk) 12:12, 26 October 2013 (UTC)

Se is more often thought of as a metalloid than C and P because C tends to be associated with the diamond form, which doesn't look like a metal and is an insulator, and the standard state of P is white P which doesn't look like a metal and is also an insulator. Grey Se is a semiconductor and also has a conductivity many times that of other forms (although this tends to be overstated due to impurities in commercial grade Se). As well, at least in the environmental sciences, Se tends to be thought of as a metalloid or heavy metal on account of similarities in its aqueous chemistry with As and Sb. Other 'metallic' properties of Se are given in the metalloid article, under Selenium. Sandbh (talk) 00:16, 27 October 2013 (UTC)

By my reckoning, and for the following fifteen properties: first ionization energy; electron affinity; standard reduction potential; melting point (black P apparently sublimes at 394º C); boiling point; liquid range; most stable oxidation state; ductility or malleability; appearance; Goldhammer-Herzfeld metallicity ratio; band gap; conductivity; and cationic chemistry(?): Se is tied with C and black P in terms of which is more metallic, but is ahead of white P in 10 of these properties; white P is more metallic than S in 8 properties; and S is ahead of I on 9 properties (with one, cationic chemistry?) a tie. Sandbh (talk) 00:53, 28 October 2013 (UTC)

From: http://en.wikipedia.org/wiki/Wikipedia_talk:WikiProject_Elements/Archive_15#Time_to_deprecate_.27other_nonmetals.27

IMPs (incipient metallic properties) of iodine include:

• residual metallic luster;

• semi-conductivity (band gap = 1.35 ev, similar to grey Se(?));

• photoconductivity;

• electron delocalization within the layers of the solid iodine lattice;

• its metallic transformation under the application of relatively modest pressure;

• the metal-like electrical conductivity of the liquid form;

• the existence of the +1 iodine cation in pyridine solution and associated salts;

• and the polymeric structure of its most stable oxide, I2O5.

All five solid elements currently classified as nonmetals are not the best examples of nonmetals. I am not sure about larger metallicity of sulfur (compared to metallicity of iodine)... Sulfur is polyatomic, has higher boiling point, less acidic hydride, less soluble salts (can be less stable than iodides), lower electronegativity in Pauling scale, slightly lower first ionisation energy. Iodine looks better for me, not so much more metallic than sulfur. But sulfur differs from less metallic elements because of its polyatomic character and quite high melting and boiling points. Sulfur allotropes are less metallic than iodine in other charcteristics: electrical and thermal conductivity and metallic luster.

79.191.195.142 (talk) 18:00, 9 November 2013 (UTC)

Arsenic more metallic than phosphorus

The example AsPO₄ has a structure very like As₂O₄ (see Corbridge book Phosphorus: Chemistry, Biochemistry and Technology, Sixth Edition) - its is essentially a covalent mixed oxide. The so-called sulfate As₂(SO₄)₃ is an odd beast with AsO₃ trigonal pyramids (as in any arsenite). The formulae suggest straightforward ionic formulations, with As³⁺ but this is far from the truth. Axiosaurus (talk) 12:21, 2 December 2013 (UTC)

That would be worth noting. As far as I can recall, As³⁺ does not have an independent existence. The language used by Corbridge is not that helpful. Earlier he refers to AsPO₄ as a double oxide, sometimes described as arsenic phosphate. He then says, 'it is "virtually" a covalent oxide'. I'm not sure why he uses "virtually". Almost, but not quite, for some reason? It certainly is another remarkable construct, apparently made up of a network of AsO₃ 'pyramida' and PO₄ tetrahedra, joined together by all their corner atoms to form a continuous polymeric structure. Sandbh (talk) 10:20, 3 December 2013 (UTC)

For your amusement,you might also look at the series of phosphates AlPO₄ and the B, and gallium anologs. All have the berlinite structure all mimic to a lesser or greater extent SiO₂ polymorphism, AlPO₄ to a remarkable extent- it is isoelectronic with SiO₂. Axiosaurus (talk) 12:57, 4 December 2013 (UTC)

Phosphorus is generally more similar to typical metalloid (arsenic) than to typical nonmetal (nitrogen). It can even be named as a "metalloid closer to nonmetals", such as C and Se. Electronegativity of phosporus in revised Pauling scale is closer to the values of the recognised metalloids (such as B, As, Te, even Sb, Ge and Si) than other "near-metalloids" (C, Se).

AlPO₄ has 1 atom of a metal and 5 atoms of "nonmetals". BPO₄ (boron phosphate) is even more interesting. It has really high melting point and contains quite small of boron (a typical metalloid) per cent. Metallic character of phosphorus is strongly associated with marked nonmetallic properties of white allotrope (tetraatomic oligomer with low melting and boiling point). Red allotrope is more metallic, but not fully metalloidal, black (grey) is practically a metalloid, such as graphite and grey selenium.

95.49.248.144 (talk) 13:37, 7 December 2013 (UTC)

Phosphorus and bismuth sections (Elements less commonly recognised as metalloids)

From the list of metalloid lists: citation frequency of P is 5,2%, of Bi - 5,9% (Al 9,3%, C 8,5%). Phosphorus section looks especially important, because its general metallic properties looks not like N, S, Br, but like its diagonal neighbors (C and Se). Black, quite metal-looking polymeric allotrope is the most stable and is quite good conductor with narrow band gap, in revised Pauling scale P has even minimally lower electronegativity than platinum group metals (Ru, Rh, Pd, Os, Ir, Pt). What about polymeric phosphorus pentoxide? Is it stable at STP? Melting point of 580 C is very high for an oxide of nonmetal, especially if it does not contain bonds between non-oxygen (especially C-C bonds). Simple oxoacids of As have almost identical acidity (pKa) as phosphorus counterparts.

95.49.81.178 (talk) 07:59, 14 December 2013 (UTC)

Why there is no section about phosphorus? It is generally as metallic as C and Se.

194.29.134.246 (talk) 13:17, 18 December 2013 (UTC)

The list of propetries

Which list of metalloids does this refer to? Characteristic sort of implies these are the properties that define the metalloids, but I don't think that is the intention. Axiosaurus (talk) 15:07, 18 December 2013 (UTC)

No list in particular although application to the recognised metalloids would be closest. It's the same as all the other tables in the literature that list the properties of metals, metalloids, and nonmetals, without definitively saying just which elements they intend each column to apply to. I don't believe I intended 'characteristic' to mean or imply 'definitive' but if you think this may be an issue then I'd be happy to reword. Sandbh (talk) 22:03, 18 December 2013 (UTC)

Names or formulae of compounds (or both)?

Note for reference: Sometimes this article uses names for compounds; at other times formulae; and in some cases, both. I believe the approach I have tried to follow is to use just prose, with the following exceptions: (a) when saying something like, 'the oxides…readily form glasses', where the ellipsis = the formulae of the oxides in question; (b) when there is no easy prose equivalent for a compound; (c) when the formula is not obvious, in which case the formula is added after the prose; (d) when industry usage is to refer to a compound by its formula moreso than its prose name (e.g. CdTe) in which case the formula is included, even if it is simple. I had a look at WP:MOSCHEM and it doesn't address this topic. Sandbh (talk) 23:03, 23 January 2014 (UTC)

Bismuth

According to many textbooks, Bismuth is not a metalloid? AstroBlue403 6:19pm Feb 1st, 2006

Are you asking a question? From everything I've read, bismuth pretty much is the textbook example of a semimetal. eaolson 01:36, 2 February 2006 (UTC)

yoohhh, I was saying that in a lot of textbooks at our school, it says Bismuth is not a metalloid. I'm not sure, so I just put a question mark on the end. Still lots of homework to do, so I tried to make it fast on the last comment.AstroBlue403 11:46pm Feb 1st, 2006

• If you have an "official" definition of metalloid or semimetal, please feel free to put it up here, or even just the citation. Verifiability is always a good thing. I'm not yet convinced that metalloid and semimetal are exact synonyms, but haven't done significant research on it. I'm pretty sure that Bi is generally considered a semimetal, though. eaolson 20:35, 2 February 2006 (UTC)

Doesn't Bismuth form positive ions, if it does then it is a metal — Preceding unsigned comment added by Doctor mosh splosh (talk • contribs) 17:39, 4 February 2014 (UTC)

Bismuth is not a metalloid

From what I've seen (in school textbooks) bismuth is always considered a metal. The Wikipedia article on bismuth states that it is a poor metal, which Wikipedia defines as "occuring between the metalloids and the transition metals". From this BLA BLA BLAit seems that bismuth is, in fact, a real metal (though maybe not the best example of one!).

220.235.249.246 04:18, 10 February 2006 (UTC)

Agreed. Webelements.com describes all the metalloid elements as "semi-metallic", but Bismuth is described as "metallic". I'm for removing Bismuth from the list. Polonium is described as metallic too, though it is worth remembering that Chemistry is not black-and-white. CaptainVindaloo 22:26, 11 February 2006 (UTC)

I disagree. I am pretty sure that Bi has either a very small bandgap or that the conduction and valence bands overlap only indirectly. (I forget.) I will try to find some references as soon as I can. eaolson 22:49, 11 February 2006 (UTC)

On Monday, I'll check with my Chemistry teacher. CaptainVindaloo 23:02, 11 February 2006 (UTC)

Eight years later, still no evidence for the claim that bismuth is a metalloid. Now we are REALLY convinced by the claim that it is one ... Wiki itself states that it is a metal. — Preceding unsigned comment added by 92.2.218.19 (talk) 23:36, 7 February 2014 (UTC)

Aluminum is not a metalloid

The 8 metalloids are Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, Polonium, Astatine. "... the majority of known elements are metals; only 17 elements are nonmetals, and 8 elements are metalloids."(Chang, Raymond. 2005. Chemistry, Eight Edition.) Sorry, there is no direct quote saying Aluminum is not a metalloid. However there is a periodic chart showing the metals, non - metals and metalloids. It shows aluminum as a metal. —The preceding unsigned comment was added by 70.73.254.247 (talk • contribs) .

• Citation? eaolson 22:56, 15 October 2006 (UTC)

Yes please, a citation would be lovely, considering the amount of ruffled feathers over bismuth. CaptainVindaloo ^{t c e} 00:16, 16 October 2006 (UTC)

• Yeah, in my textbook, it says that Aluminum IS one. Ctifumdope 20:20, 16 October 2006 (UTC)

--Sterlinggreeson (talk) 17:38, 8 February 2013 (UTC)Aluminum is not a metalloid, it is a metal, it may be confusing because it is close to the “stair case” of metalloids, it may also be confusing because it is shiny, and it may be brittle, but that’s only in foil, when it’s a bar, its malleable, because you can have gold, or iron foil, and its brittle, but its shiny, so, if you follow that rule, you’d end up with all metals as metalloids!

Wait--neither polonium, or astatine are metalloids--they just usally say that they are. —Preceding unsigned comment added by Wd930 (talk • contribs) 01:38, 5 December 2010 (UTC) — Preceding unsigned comment added by Sterlinggreeson (talk • contribs)

---

Wait--neither polonium, or astatine are metalloids--they just usally say that they are. —Preceding unsigned comment added by Wd930 (talk • contribs) 01:38, 5 December 2010 (UTC)

For me Sn looks much more metalloidal than Al, even if it is not so close to the metal-nonmetal dividing line.

I think that Al can't be named as metalloid. Au is even more metalloidal in some ways (for example, it can create quite stable monoatomic anion). Ga looks also a bit more metalloidal than Al, such as Bi. Be is the most similar in the level of metallicity to Al.

I think that C, P, Se, maybe even iodine could be named as half-metalloids (intermediates between nonmetals and metalloids), near-metalloids. Aluminium is too metallic, it is to a higher degree a metal than C, P and Se are nonmetals. Some metals are generally poorer than Al.

95.49.248.238 (talk) 21:09, 13 November 2013 (UTC)

Indeed. Calling alluminium a 'metalloid' robs the term of all meaning. — Preceding unsigned comment added by 92.2.218.19 (talk) 23:39, 7 February 2014 (UTC)

carbocations as indicators of metallicity ? ?

Using e.g. CH₃⁺ as an indication of metallicity surprises me. Yes they exist, but do the references quoted say that their existence indicates metallicity of carbon or are you extrapolating? One could I guess argue in a similar vein that NH₄⁺, a nitrogen cation, indicates metallicity of nitrogen.Axiosaurus (talk) 13:13, 25 January 2014 (UTC)

Oh, I missed this one. Response soon. Sandbh (talk) 03:51, 8 February 2014 (UTC)

Yes, Traynham (1989, p. 930) notes that the word carbonium was introduced in analogy to metallic character:

'The term carboniumion [sic] first appeared in the chemical literature in early 1902 in an article on color theory by Adolf Baever and Victor Villiaer. Baever and Villiaer attempted to explain the color that developed when triphenylmethanol was mixed with sulfuric acid or triphenylmethyl chloride with aluminum chloride. They likened these reactions to salt formation from metal hydroxides and likened the carbon center to the metal: natrium–carbonium. The designation carbonium was apparently intended merely to convey that metal-like behavior: carbon-ium. (The strong favor toward Latin words at that time in Germany may have led to that choice instead of Kohlenstoffiuni for the new term.) Baeyer and Villiger did not use a formula representation for the carboniumsalze, and the term was used only in the generic sense. That is, it was not used as part of the name of any specific substance. The focus was clearly on the metal analogy. The originating authors used the terms carboniumsalze, carboniumnitrate, and Carbonium- und Oxonium-Salze.

Sandbh (talk) 01:12, 16 February 2014 (UTC)

Perhaps "triphenylmethanol" is the "metal" and not carbon? Personally I think its a bit of a stretch and a 1902 reference (John McEnroe famous quotespings to mind)- but if you argue that a +ve carbon entity => metallic carbon then at least mention carbanions .Axiosaurus (talk) 09:26, 16 February 2014 (UTC)

I've gone one better and added some content about carbon anions rather than 'mere' carbanions. That was a good suggestion re adding balance. Thank you. Sandbh (talk) 11:16, 18 February 2014 (UTC)

Infobox (periodic table part) content improvement

About {{periodic table (metalloid)}}, as used in this article. Content issue: currently the undisputed metalloids are colored brown   , the same as the brown category color in all our general periodic tables (with legend=metalloids). But since this article details that polonium is uncommonly classified as metalloid, it has a different color (light blue). From there, the two brown categories differentiate (Po in or out the brown group). This difference shows with the micro PT that is in top. To restore consistency, I suggest that the brown legend color in this table should change into something new & unrelated. Our general periodic tables & legends stay unchanged then. (note to self: when I have some more time, I can do this myself. By the way, there are also some layout & accessability improvements to be considered). -DePiep (talk) 10:23, 23 February 2014 (UTC)

Agree a colour change. Are there any other colours left? :) Sandbh (talk) 22:15, 23 February 2014 (UTC)

Used   #90ee90. Away from the brown, now we use a red-green-yellow-blue. -DePiep (talk) 13:20, 24 February 2014 (UTC)

Review Feb 19 by John

I took a series of hacks at the article today. It is looking very good. Besides a tendency to wordiness, I mainly fixed:

• An over-focus on definitions of terms rather than explanations of those terms; we are an encyclopaedia, not a dictionary.
• A slight confusion between groups and periods at one point
• An apparent misapprehension about alloys; it is entirely characteristic of alloys that one or more component can be a non-metal, so no "however" is required when discussing this. However is best avoided if possible.
• A slightly confusing tendency to talk for example about differences in properties of elements and their compounds as though this was unusual. It is not; sodium and sodium chloride is a canonical example
• A related tendency to talk about elements "in the form of" a compound of the element; this is correct but confusing to the non-chemist. Silicon and silicone are very different in their properties.
• In a biological context, there is no contradiction at all in an element or compound being essential in small quantities but lethal in greater quantities. Look at dihydrogen monoxide if you doubt me. This too is highly typical of biological systems' response to substances and does not therefore need to be marked with "however" or equivalent.
• Overlinking.
• We can't say one temperature is half of another temperature unless we are using absolute units. Even with that, I'm not sure comparing everything to the melting point of steel is particularly useful.
• Changed IEs from kcal/mol to the SI unit kJ/mol. WP:UNIT recommends using the SI unit on Science articles. I hadn't noticed this earlier but this would be a fail at FA.

I hope you will agree the article is improved as a result. I would like to see a few more passes by both subject specialists and prose experts (I am lucky enough to be both) before resubmitting this for FA. The sourcing is excellent. --John (talk) 11:15, 20 February 2014 (UTC)

Just looking at the un-thatched version now. Comparing b4 and after versions I can see some very impressive snipping. I'm going to have to print out and read carefully, checking for preservation of intended meaning, and nuances. More detailed feedback soon. Appreciate the compliment re sourcing. Sandbh (talk) 11:24, 21 February 2014 (UTC)

Phew, I'm glad you thought it was ok. I certainly think it reads a lot better now and I will step back from it to let you have a proper look. --John (talk) 13:54, 21 February 2014 (UTC)

At first pass most of your edits look good. A minority I'll have to look at closely. I think this will take me longer than I anticipated. It certainly is thought-provoking and insightful to be exposed to copy-editing of this order. Sandbh (talk) 03:03, 22 February 2014 (UTC)

I see you have restored kcal/mol; I don't think I agree that this is better. --John (talk) 15:21, 23 February 2014 (UTC)

Acknowledged. I have a dozen more edits to check and will then stand back and look at where things are up to, including more detailed feedback on your points above. I don't mind so much about the kcal/mol kJ/mol thing but would like to chat about that then. In the interim I've thought about listing both units as a possible solution. I much appreciate your work and ongoing interest---the article has benefited significantly. Thank you, Sandbh (talk) 22:06, 23 February 2014 (UTC)

Edit checking done. Now going to to check for orphaned references. Stand-back, and detailed feedback will then follow. Sandbh (talk) 12:15, 24 February 2014 (UTC)

John: I'm done. I have no detailed feedback as the article has sharply improved as a result of your copy-editing and trimming, thank you. It does indeed read a lot better now, and I've learnt about the value of copy-editing. I left the ionization energy values in kcal/mol as those are the units that Masterton and Slowinski used when they wrote that metalloids have ionization energies around 200 kcal/mol and electronegativity values close to 2.0. I suspect they were pleased that they were able to use such easily remembered round numbers. MOS:NUM appears to accomodate use of the older units, in a case such as this. Converting 'around 200 kcal/mol' to 'around 863.8 kJ/mol' (or should that be 837 kcal/mol) seems awkward to me. Please let me know if this would still be an issue for you. I will ask User:Dirac66 about his availability for a combined copy-editing and a subject matter expertise sweep, as I have always appreciated his ce/sme work. Sandbh (talk) 11:33, 27 February 2014 (UTC)

Re units, I take your point and could compromise on 200 kilocalories per mole (837 kJ/mol) or suchlike. --John (talk) 22:31, 27 February 2014 (UTC)

Actually, maybe 840 kJ/mol (200 kcal/mol) would be more in keeping with MoS. --John (talk) 11:36, 28 February 2014 (UTC)

Hmm. I was just about to say that I'd changed the article by adding (kJ/mol) values, when I arrived here. Let me just have a look at this again then. Sandbh (talk) 11:48, 28 February 2014 (UTC)

Wow. How does that converter work? One (thermochemical) kcal = 4.184 x 10³ joules. So 200 kcal = 836.8 kJ? Sandbh (talk) 12:03, 28 February 2014 (UTC)

It's very clever, isn't it? --John (talk) 13:52, 28 February 2014 (UTC)

See Template talk:Convert#kcal/mol to kJ/mol and vice versa. --John (talk) 21:28, 28 February 2014 (UTC)

• Coming back a week later, most of the subsequent changes look good. Two I want to query are the use of "paradoxically" to describe the selection of white phosphorus as the standard state of P; this is not a paradox. It might be described as arbitrary, expedient or even surprising (though of course any of these would need a source), but it cannot be described as a paradox. The second is the creeping back in of "however" and "although". Using terms like this has to be extremely thoughtful and in practice should almost never be done because of NPOV concerns. Other than these two comments I think it looks great. --John (talk) 19:49, 5 March 2014 (UTC)

That's beaut! Thank you very much. 'Paradoxically' has been fixed. I found two 'however's and twelve 'although's. One 'however' is in a quote; the other one has been copy edited away. I replaced one 'although' with a more direct 'but'. Six others have been copy edited away (possibly back to the way you did in some cases, as it's taken me some practice to write like that). Two of the remaining 'although's are used in an explanatory sense. The other three don't appear to raise unsupported implications, as far as I can see. Sandbh (talk) 11:21, 6 March 2014 (UTC)

I think the paradox (for nonexpert readers) is that the least stable form is the most common. The origins of the metastability can be addressed in the article on phosphorus.

Also I have just revised the article standard state which claimed that for (all) elements the standard state is defined as the most stable allotrope. I have inserted a mention that phosphorus is an exception. Dirac66 (talk) 14:51, 6 March 2014 (UTC)

Comments as requested

My name has been suggested above for a combined copy-editing and a subject matter expertise sweep. After a quick reading, I think that (1) the copy-editing is very good already, and (2) as a physical chemist I am not really a subject matter expert in this type of inorganic chemistry. However I will make a few comments.

Many thanks for these.

The charts showing which elements are included are arbitrary. The first color chart shows elements ascommonly recognized, inconsistently, less commonly, rarely. Do we have a source for these categories? Or is this OR by some editor based on ... what exactly? But the chart in the section Location is probably worse, as the category Common to rare includes for example C, Si, and Ge. This suggests that comparable numbers of chemists consider C and Si to be metalloids - I doubt that this is true. Perhaps the best solution would be to use a chart (or two) directly from a widely used book or review article. That would still be arbitrary but at least it would not be OR.

The names of the categories in the first colour chart are the simplest descriptive labels I could come up with. They're based mainly on three review articles and two books (and the content and sources in the Main article: List of metalloid lists):

• Chedd G 1969, Half-Way Elements: The Technology of Metalloids, Doubleday, New York
• Rochow EG 1966, The Metalloids, DC Heath and Company, Boston
• Goldsmith RH 1982, 'Metalloids', Journal of Chemical Education, vol. 59, no. 6
• Hawkes SJ 2001, 'Semimetallicity', Journal of Chemical Education, vol. 78, no. 12
• Vernon RE 2013, 'Which Elements Are Metalloids?', Journal of Chemical Education, vol. 90, no. 12

The terminology used in these and other sources varies.

Commonly recognised. Rochow (pp. 1–8) says B, Si, Ge, As, Sb and Te come firmly within his qualitative and (single) quantitative criteria. Chedd (p. 14) asserts that B, Si, As, Ge, Sb and Te can 'truly' be called metalloids. Goldsmith (1982) says the elements mentioned most frequently as metalloids are B, Si, As, Ge, Sb and Te. Mann et al. (2000, p. 2783) refer to these elements as 'the recognized metalloids'.

• Mann JB, Meek TL & Allen LC 2000, 'Configuration Energies of the Main Group Elements', Journal of the American Chemical Society, vol. 122, no. 12

Inconsistently. Rochow is in two minds about Po and At. He first shows them as metalloids on his periodic table (p. 3), and then leaves open the question of whether they 'are (or are not) metalloids…' (p. 8). Chedd says that Po and At 'might' be considered metalloids. He later changes his mind and says they are metalloids (pp. 14, 24). Goldsmith (1982) says Po and At are 'sometimes' included in metalloid lists. Hawkes (2001) says most metalloid lists, 'exclude either polonium or astatine or neither but not both.' He then wrote a series of articles disputing the metalloid status of At, and later changed his mind (Vernon 2013). Holt, Rinehart, and Wilson (c. 2007) dispute the metalloid status of Po and At. Cobb (2012, p. 145) adds Po to his list of elements commonly recognised as metalloids (B, Si, Ge, As, Sb and Te).

• Cobb HM 2012, Dictionary of Metals, ASM International, Materials Park, OH
• Holt, Rinehart & Wilson c. 2007 'Why Polonium and Astatine are not Metalloids in HRW texts'

Personal observation: It's relatively easily to find examples in the literature of metalloid lists supporting what the above sources say.

Less commonly. Selenium is an oddity. Rochow (1957, p. 224) says that, 'In some respects selenium acts like a metalloid and tellurium certainly does.' Meyer et al. (2005, p. 284) says that '…Selenium traditionally is considered a metalloid in aquatic chemistry...'. It transpires that this is because Se moves through the aquatic environment like arsenic and antimony do (US Environmental Protection Agency 1988, p. 1; Uden 2005, pp. 347‒8). And its water-soluble salts, in higher concentrations, have a toxicological profile similar to that of arsenic (De Zuane 1997, p. 93; Dev 2008, pp. 2‒3). Weiner (2012, p. 181), writing on the behaviour of metal species in the aqueous environment, says it often happens that 'little or no distinction is made between metals and metalloids, especially for the metalloids As, Se and Sb, which are often classifed with metals in tables of standards...discharge limits, chemical properties, "and so on".' He adds a note saying that Se is most commonly listed as a nonmetal, like sulfur, however some crystalline forms resemble metals closely enough that it is sometimes called a metalloid. Vernon (2013) says the electronegativity of Se is too high to warrant calling it a metalloid.

• Dev N 2008, 'Modelling Selenium Fate and Transport in Great Salt Lake Wetlands', PhD dissertation, University of Utah, ProQuest, Ann Arbor, Michigan
• De Zuane J 1997, Handbook of Drinking Water Quality, 2nd ed., John Wiley & Sons, New York
• Meyer JS, Adams WJ, Brix KV, Luoma SM, Mount DR, Stubblefield WA & Wood CM (eds) 2005, Toxicity of Dietborne Metals to Aquatic Organisms, Proceedings from the Pellston Workshop on Toxicity of Dietborne Metals to Aquatic Organisms, 27 July–1 August 2002, Fairmont Hot Springs, British Columbia, Canada, Society of Environmental Toxicology and Chemistry, Pensacola, FL
• Rochow EG 1957, The Chemistry of Organometallic Compounds, John Wiley & Sons, New York
• Uden PC 2005, 'Speciation of Selenium,' in R Cornelis, J Caruso, H Crews & K Heumann (eds), Handbook of Elemental Speciation II: Species in the Environment, Food, Medicine and Occupational Health, John Wiley & Sons, Chichester, pp. 346–65
• US Environmental Protection Agency 1988, Ambient Aquatic Life Water Quality Criteria for Antimony (III), draft, Office of Research and Development, Environmental Research Laboratories, Washington
• Weiner ER 2012, Applications of Environmental Aquatic Chemistry: A Practical Guide, 3rd ed., CRC Press, Boca Raton, FL

Personal observation: In my experience of reading the literature, Se is the next most frequently found element in metalloid lists, after the commonly recognised metalloids.

Rarely. Rochow (1966, pp. 7–8) says that 'for one reason or another,' it is sometimes desirable to think of neighbouring elements such as C, P and Bi as metalloids (he later says P, Bi and Se). Hawkes (2001) further says that 'lists of "semimetallic" elements differ' and that 'Most exclude bismuth and selenium…'. Aluminium is sometimes classified as a metalloid (Cobb & Fetterolf 2005, p. 64; Metcalfe, Williams & Castka 1974, p. 539). Cobb (2012, p. 145) says that Se and Bi are sometimes included as metalloids. Vernon (2013) cites the List of metalloid lists and says 'of the menagerie of other elements occasionally identified as metalloids'—over and above B, Si, Ge, As, Se, Sb, Te, Po and At—that carbon (9), Al (9) and Bi (6) are the front runners. (Figures = % appearance frequencies from the List of metalloid lists.) Then there are the outriders: elements not specifically mentioned by Chedd, Rochow, Goldsmith or Hawkes, but for which isolated references to their categorisation as metalloids can nevertheless be found in the literature, as given in the List of metalloid lists.

• Cobb C & Fetterolf ML 2005, The Joy of Chemistry, Prometheus Books, New York
• Metcalfe HC, Williams JE & Castka JF 1974, Modern Chemistry, Holt, Rinehart and Winston, New York

Personal observation: It's hard to find examples of metalloid lists in the literature that include C or Al, (or even P or Bi) but they're out there.

Quote But the chart in the section Location is probably worse, as the category Common to rare includes for example C, Si, and Ge. This suggests that comparable numbers of chemists consider C and Si to be metalloids - I doubt that this is true. Unquote

Oh, the 'Common to rare' category means the elements so coloured have appearance frequencies ranging from common (Si, Ge) to rare (C). This is explained in the text accompanying the chart: 'Elements with grey shading (B, C, Al, Si, Ge, As, Se, Sb, Te, Po, At) appear commonly to rarely in the list of metalloid lists.'

Words describing atomic or bulk properties should be wikilinked on first appearance. For example, ionization energy, electronegativity, conductor, insulator, semiconductor.

Will check for missing links.

The section title Typical or shared applications is confusing. What exactly is a shared application? Also this section on applications should probably be placed later in the article.

'Shared' was intended to mean an application that is common to some, but not all metalloids. I'll change the title to 'Common applications' as I reckon this covers both meanings well enough. The location of this section has been the subject of previous comments. It is where it is now because the main focus of the article, it was suggested, should be on metalloids, not so much their individual properties (although this is still pertinent).

Done Sandbh (talk) 11:14, 3 March 2014 (UTC)

Organometallic compounds of boron have been known since the 19th century. But can we speak of organometallic compounds of boron if boron is not a metal? I would prefer to say Organoboron compounds have been known since the 19th century, and are similar to organometallic compounds. Similarly the references to organometallic chemistry of Ge, As, Sb and Te should be changed. The last sentence on Si is more acceptable: Traditional organometallic chemistry includes the carbon compounds of silicon (see organosilicon), as it does not actually say that organosilicon compounds are organometallic.

I'm inclined to do this but let me check my notes on metalloids in organometallic chemistry.

Looking through my papers, it's apparently a long standing tradition that organic compounds of the metalloids fall within scope of the definition of organometallic compounds. See, for example, the IUPAC Gold book definition and the Author guidelines for the ACS journal, Organometallics. (I had a feeling there was a reason I worded these parts of the article the way I did). I've added a note to this effect. Sandbh (talk) 11:14, 3 March 2014 (UTC)

Carbon: the formulas of some ionic salts (sulfate, perchlorate) would be of interest. On the other hand, much of the last part of this section is irrelevant to any metalloid nature of carbon - I would delete organic carbocations, as well as all the anions and carbonic acid.

Will add formulae. The mini-bios of each element are generally divided into metallic properties and non-metallic properties. Unless you consider it a showstopper I'd prefer to keep carbocations, as the carbocation nomenclature originated with reference to metal-like behaviour by carbon. Mention of carbon anions and carbonic acid is intended to show the nonmetallic behaviour of carbon.

Formulae added Sandbh (talk) 12:00, 3 March 2014 (UTC)

Finally, Honourable mentions is an overly cute section title. Perhaps delete the title and just have two separate sections for Near metalloids and Allotropes. Dirac66 (talk) Dirac66 (talk) 02:15, 1 March 2014 (UTC)

I used 'Honourable mentions' to avoid giving undue weight to the 'near metalloid' nomenclature. I'll change it to 'Nearby elements and allotropic phases'. Sandbh (talk) 10:44, 2 March 2014 (UTC)

OK, thanks for the detailed replies. Much of this new information would improve the article. It is probably best that you consider exactly what to add, since it is clear that you have read extensively on this subject. I have merely added a few wikilinks which was very easy. Dirac66 (talk) 00:27, 3 March 2014 (UTC)

Cheers, and it was good to see that you added those links. 11:14, 3 March 2014 (UTC)

The basis and supporting sources for the simple descriptive category labels are given, albeit in less detail, in the Main article, List of metalloid lists. Is this an acceptable approach? I do intend to make some fine tuning adjustments to the text in List of metalloid lists, in light of the above elaboration. Sandbh (talk) 11:41, 7 March 2014 (UTC)

Yes, I agree that placing these lists in another article is a good idea, especially since this article is quite long already at 200K. Dirac66 (talk) 12:10, 7 March 2014 (UTC)

Super. Adjustments done. Sandbh (talk) 04:01, 8 March 2014 (UTC)

Aluminium is not a metalloid

Classing it as one robs the term of any meaning. — Preceding unsigned comment added by 92.2.218.19 (talk) 23:34, 7 February 2014 (UTC)

I somewhat agree. However, there is no standard division of the elements into metals, metalloids and nonmetals. And there is a more or less continuous progression from the metallic to the nonmetallic. A specified subset of this continuum, i.e. one which includes Al as a metalloid, can potentially serve its particular purpose as well as any other. Having said that, most authors would treat Al as a metal. Sandbh (talk) 11:26, 4 March 2014 (UTC)

I would personally use the metalloid designation only for elements where it is not immediately obvious (after a quick glance at physical and chemical properties) whether metallic or nonmetallic properties dominate, and I suspect most authors would do so as well: but there may be good reasons for treating other elements, whose properties are weighted more on one side or the other, together with the metalloids.

Why does including Al "[rob] the term of any meaning"? It has claims to metalloid character, although definitely not as strong as the next element in the period, Si. For instance, Al has important nonmetallic properties (e.g. amphoteric oxide, many compounds have covalent character) while still having the expected strong electropositivity of a metal. There are good reasons for such a classification, even though I would personally not make it my general classification (perhaps I would use it for specialized purposes). Double sharp (talk) 12:34, 11 March 2014 (UTC)

Gallium also has an amphoteric oxide, it is very similar to Al in much of its chemistry. It has Ga₂ units in the metal, which is VERY low melting by metal standards, but in spite of all of this is not a classed as a metalloid, funny that. Article is fine - as someone (misguidedly IMO) once said that Al is metalloid (probably just because it is next to the Zintl border and follows boron and "therefore should be" ) then it has to be mentioned. Axiosaurus (talk) 17:24, 11 March 2014 (UTC)

Axiosaurus: Are you aware of any precedent for calling the dividing line between metals and nonmetals the Zintl Border? There are a few sources that call it by this name however I've not been able to determine the origin of this practice. As I understand it the Zintl Border still formally refers to the line between groups 13 and 14? I don't know but presumably some author must have thought the dividing line between metals and nonmetals ought to be given a name and perhaps decided to borrow the Zintl Border handle. I suppose if such a thing can happen to a term such as metalloid, which is currently in its third meaning incarnation then the same thing could happen to Zintl Border. But Zintl Border has retained its original meaning and is still being used in that sense. Grateful for your thoughts. Sandbh (talk) 10:49, 12 March 2014 (UTC)

Sorry , the only reference I have is Encyclopedia of Inorganic chemistry 1994, ed R Bruce King. Inside cover shows the infamous ladder as "Zintl border"- and the entry on p 4467 says "step like separation of metals and non-metals of the periodic table, it runs from B and Al diagonally from the top left of the main group elements of group 13 to 18." No reference is given. Zintl himself did say splitting 13 and 14. This whole area is fuzzy, full marks for trying to tame it!Axiosaurus (talk) 17:07, 12 March 2014 (UTC)

Cheers. I suspect King was the first time I saw the line called that. Which I found surprising as I'd already by then heard of the Zintl Border between 13 and 14. I'll see if I can ask King why he used ZB in his Encyclopedia. Sandbh (talk) 22:17, 12 March 2014 (UTC)

Ga has very occasionally been classified (in this instance together with Al, Sn, Bi, and Po) as a metalloid: see Selwood PW 1965, General chemistry, 4th ed., Holt, Rinehart and Winston, New York, inside back cover. I do think though that Al's position right next to the dividing line, as opposed to Ga's, has resulted in it being called a metalloid more frequently (though it's still not a majority view at all). Double sharp (talk) 13:19, 12 March 2014 (UTC)