So , I have done some searching and found that melting points of groups 17 and 18 increase going down the group whereas group 1 decreases.
However , the explanation seem to all be the same.
Number of shells increase
atomic radii increases
Van der waals force between atoms increases
more heat energy needed to overcome said forces
But for group 1, the explanation is that even when atomic radii increases , the metallic bond between atoms decreases and thus lower melting point.
So , I'm a little confused about this metallic bond , and why doesn't group 1 alkali metals also create Van Der Waals forces?
I may be wrong on some parts so please do correct me.