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January 9

Element 172

Extended periodic table: "Element 172 (unseptbium) is expected to be a noble gas with chemical behaviour similar to that of xenon, as their ionization energies should be very similar (Xe, 1170.4 kJ/mol; element 172, 1090 kJ/mol). The only main difference between them is that element 172, unlike xenon, is expected to be a liquid or a solid at standard temperature and pressure due to its much higher atomic weight." However, due to the periodic trends, Uub is the 8th noble gas, and it should be more reactive than Og (the 7th noble gas), and it should have higher melting point and higher boiling point than Og, but Og is reactive and it is excepted to be a solid at standard temperature. 2402:7500:918:A8FE:A474:8A0A:804A:9C97 (talk) 06:58, 9 January 2024 (UTC)[reply]

You're not really comparing like with like, because relativistic effects mean that the late 8th period is a different situation from the late 7th period in terms of orbital energies and the order of filling. To oversimplify it: down the table, noble gases increasingly don't think they have a full shell because np_3/2-(n+1)s_1/2 gap gets smaller. (Ng⁺ monocations in excited states with energies under the first ionisation energy of the noble gas can populate (n+1)s for Kr, Xe, and probably Rn and Og, but not for Ne and Ar.) But by the time you hit element 172, this gap becomes negative, so it's really the np_3/2-(n+2)s_1/2 gap that now matters, and that's huge. You can kind of see what's going on in the figure to the right (although it doesn't have 10s there yet).

In the late 7th period, due to the spin-orbit interaction, the 7p subshell is split into one more stabilised p-orbital (7p_1/2) and one less stabilised p-orbital (7p_3/2). The split is so much that by the time 7p_3/2 fills, it's not actually that far from 8s in energy. 7s_1/2 is also quite stabilised by relativistic effects. So what happens is that Cn (6d¹⁰7s²) acts like a closed shell (more so than Hg), that Fl (7s²7p_1/2²) also acts like a closed shell (also more so than Hg), and finally Og (7s²7p_1/2²7p_3/2⁴) "thinks" it is a tetravalent element with four valence electrons and should be able to involve 8s in hybridisation.

Whereas in the 8th period, this happens to such an extent that by the time you get to elements in the 160s or so, 8s is already in the core, and so is 8p_1/2. Instead, 8p_3/2 is so destabilised that it ends up very close in energy to 9s and 9p_1/2. Consequently, the situation from elements 157–172 is that 7d_3/2, 7d_5/2, 9s_1/2, 9p_1/2, and 8p_3/2 are quite similar in terms of energy differences to the way 4d_3/2, 4d_5/2, 5s_1/2, 5p_1/2, and 5p_3/2 behave in the fifth period. On the other hand 10s_1/2 is much higher in energy, and in essence that's the next valence shell just like 6s_1/2 is for xenon. That makes 172 resemble a super-xenon.

(Obligatory caveat that we don't really know if elements that heavy will be stable enough to even call chemical elements.) Double sharp (talk) 09:04, 9 January 2024 (UTC)[reply]

If the reciprocal of the fine-structure constant is 299792458 rather than 137, then the physical properties and the chemical properties of the elements in the period 8 will be completely different? 2402:7500:918:A8FE:A474:8A0A:804A:9C97 (talk) 09:39, 9 January 2024 (UTC)[reply]

The higher the reciprocal of α, the weaker the electromagnetic interaction is between particles. So atoms would, to put it bluntly, instantly fly apart due to electromagnetism being very weak.

I do wonder how long a hydrogen atom would last if α = 1/c instead of around 1/137. Stoplookin9 (talk) 02:55, 10 January 2024 (UTC)[reply]

The fine-structure constant, being dimensionless, cannot be equal to 1/c, as that would have a dimenion of inverse velocity. By choosing different units of measurement, I could make the numerical value of c anything I like, including 1/α. PiusImpavidus (talk) 09:10, 10 January 2024 (UTC)[reply]

In the Hartree atomic units, the value of

c

is

1/\alpha

. 2402:7500:901:720D:FC88:A133:EB79:3B45 (talk) 14:05, 12 January 2024 (UTC)[reply]

Denis Walsh on Evolution?

What is the current view of evolution biologies about the ideas of the university of Toronto professor Denis M. Walsh?
Is his view werth to consider it? 2A02:8071:60A0:92E0:D059:5B33:4DE5:1E8 (talk) 22:21, 9 January 2024 (UTC)[reply]

He is a philosopher of science or historian of science rather than a biologist. tgeorgescu (talk) 22:51, 9 January 2024 (UTC)[reply]