Question

What are some examples of halogens?

Answer 1

All the group 17 (7B) elements except astatine are definitively considered halogens.

So, fluorine (`"F"`), chlorine (`"Cl"`), bromine (`"Br"`), and iodine (`"I"`) are the known, definitively accepted halogens. Astatine is bit of a problem child, being radioactive, and rapidly vaporizing and all...

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Basically the lowdown on astatine's oddball self is:

This person clearly states that although it's just speculation due to his interpretation of someone else's potentially problematic relativistic density functional theory calculations (including the relativistic effects of `1s`-orbital contraction and spin-orbit coupling)...

...it is unclear/disputed how "halogenic" the condensed-phase astatine really is (y'know, before it rapidly vaporizes).

I guess its speculated metallic character isn't so surprising though...

• Fluorine is a gas.
• Chlorine is a denser gas.
• Bromine is a liquid.
• Iodine is a solid.
• Astatine has an apparently unknown density for some sources, but here, the melting point is over twice that of iodine...

For now, I think we should put the idea of astatine as a definitive halogen aside.