Chemistry – The Periodic Table - Group VII properties | e-Consult

The Group VII halogens (chlorine, bromine, and iodine) are diatomic non-metals, existing as molecules (Cl₂, Br₂, and I₂). Down the group, density increases due to increasing atomic mass. This is because the halogens become heavier as you move down the group. Reactivity decreases down the group. This is because the effective nuclear charge on the valence electrons decreases, making them less attracted to other atoms and therefore less likely to participate in chemical reactions. Iodine is the least reactive, while chlorine is the most reactive.