Talk:Properties of nonmetals (and metalloids) by group

Astatine

Isn't astatine (usually) classified as a nonmetal or metalloid, rarely a metal? Even polonium is sometimes classified as a metalloid, though usually a metal.174.103.211.175 (talk) 04:19, 8 December 2024 (UTC)

It depends on what one means by "metal" and how much weight one puts on predictions. Astatine is calculated to metallise at standard conditions: the halogens metallise at lower pressures as one goes down the group, and apparently relativity should play the deciding role in pushing At to be already metallic at 1 atm (10.1103/PhysRevLett.111.116404). On the other hand, this is currently impossible to actually demonstrate. If one looks at trace-level chemistry, then what we know of At chemistry looks somehow less traditionally "metallic" than Sb. I would also suspect that it currently looks more metallic than it really "should be" because we can only examine it at extreme tracer concentrations, just like how at such concentrations the equilibrium shifts away from I₂ and towards HIO. Against that we would have to note that the typical high-school notion of chemical "metallicity" (forming cations when dissolved in water etc.) does not really apply to heavy transition metals like W and Re.

P.S. regarding polonium: Po has no band gap while Te does, but HgPo has the rock salt structure while HgTe has the zincblende one. :) Double sharp (talk) 13:53, 9 December 2024 (UTC)

P.P.S. but yeah, mostly people tend to assume that since the lighter halogens are nonmetallic, At also should be. Not really a big deal considering how unimportant At is in the grand scheme of things, but yeah, it's probably not true. Double sharp (talk) 10:08, 17 December 2024 (UTC)