Question

What is periodic trend in the variations of the valency while going down the group?explain your ans with reference to group 1 ,2 and 18

Answer 1

In a group, outer electronic configuration is same for all the elements so all have the same number of valence electrons and therefore the valency.
In Group 1, all the elements have valency = 1
In Group 2, all the elements have valency=2
But in Group 18, the electronic configuration of the last shell has a complete octet. Due to which the last group that is group 18 has zero valency.