Question

name three elements which have seven electrons in their outermost shell. How do their non-metallic character and size change down the group.

Answer 1

Halogens have 7 electrons in the outermost shell, in serial order the first three halogens are:
F = 9 = 2,7
Cl = 17 = 2,8,7
Br = 35 = 2,8,18,7

As we can see the atomic no. is increasing and so the no. of orbitals also hence size increases as we go down the group.
Non-metallic character decreases as we ho down the group due to increase in size the distance between nucleus and valence orbital increases making donation of electrons easier than accepting i.e nonmetallic character decreases.