Answer:
We can calculate the number of valence shell electrons by the group number from group number ,for 1 and 2 group,1,2 are valency or charge simply,for groups lying 3–8(boron to helium family)if number is between 3–4 the group number is the charge,if number lies between 5–8 then add -8 to it,it will give a -ve which would imply it's affinity for electron
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