Question

if number of valence electrons are given then how can we find the group number of an element of an element ?

Answer 1

the valence electrons itself tells us about the group number.
if elements valence electrons is 4 then it will belong to group 4.

Answer 2

ANSWER...

THE GROUP OF ELEMENTS CAN BE DEFINED BY THE NUMBEF OF VALENCE ELECTRON THEY HAVE..

EXAMPLE...

Na has valance electron--1
so it's group is 1

while after if the valence electrons are greater than 2 then the group number will be..

valance electrons +10.

EXAMPLE..

NITROGEN HAVE VALENCE ELECTRON 5...SO ITS GROUP WILL BE...
5+10=15 GROUP...

HOPE IT HELPS