Question

How do you claculate the valency of an element from it electronic configuration.

Answer 1

HERE IS YOUR ANSWER

In general , valency is the 'combining capacity of ' of an element. To get the valency of an element from electronic configuration ,we must see the electrons present in its outermost shell which are called valence electons.

But valence electons = valency of an atom only when electon present in its outermost shell are less than or equal to four.
To find the valency of an element whose valence electons ( i.e no.of electrons present in its outermost shell ) are greater than four than subtract valence electrons from eight.

For ex. 1) Li( atomic no. 3) : 1s^2 2s^1 , valence electon is 1 therefore valency is also

2) N(atomic no. 7) : 1s^2 2s^2 2p^3 , electrons in outermost shell are( 3+2)= 5 ..since it is greater than 4 ..subtract the no. of valence electon from 8.. i.e 8-5= 3 .
Therefore valency of nitrogen is 3 and as mentioned earlier valency is the combining capacity of an element , hence nitrogen can form only 3 bonds
HOPE IT HELPED YOU DEAR!