Question

How to calculate civalency of element in a compound?

Answer 1

Covalency of a element means how many maximum covalent bonds it can form.

The term Covalency is only for smaller elements which can form covalent because the larger elements show variable valency , so for them valency term is replaced by oxidation state or number.

i.e of period 1, 2 of p- block .

B,C,N the Covalency is 4 . Can be seen in compounds like BH4-, CH4, NH4+

For Oxygen Covalency is 3 in O3 .

For Fluorine Covalency is 1 . Etc.

Note : Covalency or valency is used only with period 1 &2 elements of p- block but after that elements can expand its Octet due to d- orbitals.

From third period onwards the term valency or Covalency is replaced by oxidation state or oxidation number.