how to find valency

 

Hi,

 

Valency is defined as the number of electrons gained or lost by an atom. The electrons present in the last shell determine the valency of a particular element. If,

·   Number of valence electrons ≤ 4

·  Number of valence electrons >4

If you consider the element‘magnesium’and write down its electronic configuration, it comes out to be 2, 8, 2. The electrons present in the outermost shell are 2 (which is less than 4), so the valency is equal to 2.

However, for element ‘oxygen’ the electronic configuration is 2, 6. The electrons present in the outermost shell are 6 (which is greater than 4), so the valency is equal to 8 – 6 = 2.

 

Hope it helps.

Cheers!