User:Double sharp/Halogen

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The halogens are a group (column) in the periodic table consisting of the chemical elements fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and possibly also the synthetic element tennessine (Ts). This group lies in the p-block of the periodic table of elements as all halogens have seven valence electrons, arranged in the electron configuration ns2np5. Since all the halogens are one electron short of a full octet, they exhibit well-characterised homologous behaviour and provide one of the the best examples of group trends in properties in the periodic table.

In their standard states, the halogens are all quite volatile

say something about diatomicity (sharing)

Oh dear I've gotten myself stuck into the astatine problem again, haven't I? I think I need to take care of occurrence in the first paragraph so I can mention that At is rare because it's so radioactive so a negligible amount accumulates from U decay (and Ts is even more ephemeral, but has no naturally occurring parent). Then we can sya that not much is known about it