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November 8

Reaction of polonium with acids

What are the products of the reactions of Po metal with HNO₃ or H₂SO₄? Are salts of the respective anions formed, or does one get polonium dioxide or polonous acid instead? Double sharp (talk) 04:25, 8 November 2023 (UTC)[reply]

According to a 1983 review on Po chemistry (10.1524/ract.1983.32.13.153), at least the result for sulfuric acid was not really known:

The metal dissolves readily in dilute mineral acids with the initial formation of a pink solution (Po(II)) which oxidizes rapidly to yellow polonium(IV) species. Like selenium and tellurium, the metal reacts with sulphur trioxide and with concentrated sulphuric or selenic acids to yield bright red solids which were originally formulated [39] as PoXO₃ (X = S, Se); these may be analogous to the polymeric selenium and tellurium compounds [40], but it is doubtful whether they contain polymeric cations, such as Po₄²⁺, for the compounds dissolve completely in water to yield a solution containing polonium(II) only, in contrast to the selenium and tellurium analogues which yield precipitates of the elements with water, presumably because of disproportionation. Both polonium compounds decompose spontaneously to PoO on standing, but this does not provide any additional evidence for the make up of these compounds.

Apparently, Po(NO₃)₄ as such was not known. Do any more recent sources address this? Double sharp (talk) 07:51, 8 November 2023 (UTC)[reply]

Given that we are talking about polonium, should we be at all worried about why? ;-) (but seriously, folks, don't try working with polonium at home or if you are not a trained professional) --OuroborosCobra (talk) 17:30, 8 November 2023 (UTC)[reply]

LOL no, this is strictly theoretical. Just curious about whether it behaves more like tellurium or more like bismuth. It really is a pity that the metal-nonmetal boundary dives into dangerous territory in period 6. :) Double sharp (talk) 03:17, 9 November 2023 (UTC)[reply]

How dangerous is ²⁰⁹Po? --Lambiam 10:45, 9 November 2023 (UTC)[reply]

While I'm not 100% certain on how dangerous it is, it isn't naturally occurring. Polonium-209 only exists synthetically, with polonium-210 the naturally occurring form, is generated in uranium and radium decay chains, and is notoriously very dangerous. Polonium-209 undergoes both alpha and beta decay (unlike 210 only having alpha decay), and beta radiation is generally more dangerous than alpha, especially since alpha is very easily blocked. However, the much longer half life of polonium-209 and the vast majority of its decay is still alpha... might make that much less of a risk. Basically all of our polonium safety information on Wikipedia is for polonium-210, again since that is the naturally occurring form and the one most widely used for various legitimate (and some illegitimate) applications. I could do some more digging or back of the napkin calculations, but given that inhaling only about half a milligram of plutonium-241 oxide (half-life of 24110 years) is incredibly likely to give you cancer, and polonium-209 has a half-life of about 125 years, I'd say that polonium-209 is still incredibly dangerous. Probably more so than fissile plutonium. It's just best to not work with polonium (no matter the iosotope) at all unless you are highly skilled, well trained, and have very good engineering controls and PPE in place. --OuroborosCobra (talk) 16:13, 9 November 2023 (UTC)[reply]

Alpha radiation isn't very dangerous as long as the source is outside your body (I think the dead layer of cells at the top of your skin blocks most of it, though I would need to check that).

It's super dangerous inside, especially if the source stays in one place, say a particle in your lung. That's the reason for your point about inhaled plutonium. The alphas keep irradiating that local bit of tissue, and are absorbed almost immediately, in that same spot.

So it's not really possible to compare these risks directly without saying more about the exposure modality. --Trovatore (talk) 19:57, 9 November 2023 (UTC)[reply]

I'm aware of that, which is why I listed the inhalation risk for plutonium oxide as my source of comparison for polonium risk. I also said that alpha radiation is very easily blocked, and that beta radiation is more dangerous. I'm not exactly sure why you've given me this response, since I basically said or addressed all of that. As for polonium-209, a novice is not likely to have the proper training, engineering controls, and PPE to prevent inhalation hazards. So... they shouldn't be working with alpha emitters. --OuroborosCobra (talk) 14:48, 10 November 2023 (UTC)[reply]

Well yes, you said beta radiation was "more dangerous", without qualifying it with something like "outside the body". Alpha radiation is, as I understand it, more dangerous when the source is inside the body, for precisely the same reason it's less dangerous outside (faster deposition in tissue; makes it more easily blocked). --Trovatore (talk) 17:04, 10 November 2023 (UTC)[reply]

@OuroborosCobra: I now see that you specified Pu-241 (which is a beta emitter) but then gave the half-life for Pu-239 (which is an alpha emitter). Which did you mean? I'm pretty sure I thought Pu-239 was the one implicated in lung cancer. --Trovatore (talk) 20:47, 9 November 2023 (UTC) [reply]

The reaction between the reagents you mention would yield polonium tetrasulfide, nitrogen dioxide, and hydrogen gas. Fotzendurchfall (talk) 03:27, 9 November 2023 (UTC)[reply]

Interesting, do you have a source? (If true, the production of H₂ is illuminating; it cannot be produced chemically based on Po's electrode potential. So that would indicate radiolysis as a major factor, as expected for Po, but rather muddying the periodic trends.) Double sharp (talk) 03:46, 9 November 2023 (UTC)[reply]

I think there's only 1 active inorganic PhD here, so maybe you already have, but you're better off asking at Chemistry.StackExchange or Reddit Chempros.

But I'll bite with another question, if an element is radioactive, can it lose that when it bonds to form an ionic or covalent compound? 170.76.231.162 (talk) 15:40, 9 November 2023 (UTC).[reply]

No. Radioactive decay is nuclear, chemistry basically deals with the properties of the electrons outside of the nucleus. You need to ask the question the other way around: when a nucleus undergoes decay and becomes another element, what then happens to the compund? Martin of Sheffield (talk) 16:14, 9 November 2023 (UTC)[reply]

Something like this is possible for electron capturers with a low decay energy. The half-life of ⁷Be changes up to 1.5% depending on its chemical environment. It is stable when stripped of electrons as a bare ion. Double sharp (talk) 16:19, 9 November 2023 (UTC)[reply]

No. The impact of the electron cloud (especially when we are talking about highly radioactive elements that tend to be heavy and have high electron counts) on the nucleus is basically null. Radioactive decay is a nuclear process, so its the nucleus that's doing things. In fact, we depend upon this property (or lack of property?) for a lot of things. Carbon-14 dating, for example, basically depends upon the fact that living organisms uptake carbon-14 from the air and incorporate it throughout our bodies in compound form, with no change in the decay rate. When we die, we stop taking in new carbon-14, but the existing is still in compound form, with an unaltered decay rate. The fact that we can only specify a single decay rate for a given isotope is another example of this. If the decay rate changed depending upon what compound it was in, regardless of covalent or ionic, we would need to list decay rates for every known compound for a given isotope. We don't because it isn't impacted. --OuroborosCobra (talk) 16:19, 9 November 2023 (UTC)[reply]

The situations where decay rates actually change appreciably are illuminating: they either involve low-energy electron capturers (e.g. ⁷Be), or they involve beta decayers where the Q-value is tiny and the beta particle would have to get emitted with an energy level in the middle of an electron cloud, thus getting frustrated by Pauli exclusion (e.g. ¹⁸⁷Re). Only in these rather weird cases is the assumption in OuroborosCobra's comment very noticeably false, and even then, it doesn't tend to matter that much because you'd have to go way down to impacting the inner electrons (which chemistry can't really do) before any big differences happen. ⁷Be has the biggest effects here because it has only four electrons in the first place.

Alpha and SF rates should be affected by charge density near the nucleus, because it affects the height of the Coulomb barrier. In ordinary conditions, this should only be a 0.1%–1% difference in half-life. Double sharp (talk) 03:10, 10 November 2023 (UTC)[reply]

Alas, all the searching I've been doing before and after asking suggests that nobody has actually published new results on this since the Cold War ended or so. Hopefully I'm wrong. :( Double sharp (talk) 16:22, 9 November 2023 (UTC)[reply]

Why are you "hopefully" wrong? --OuroborosCobra (talk) 16:28, 9 November 2023 (UTC)[reply]

Because I'd find the answer interesting, and if I'm right about this, nobody knows what it is. :) Double sharp (talk) 02:56, 10 November 2023 (UTC)[reply]