Question

An atom has 4 protons and 5 neutrons.what is its valency?

Answer 1

protons=atomic number
∴atomic number=4
∴electronic configuaration=2,2 
∴valancey=2

Answer 2

Its valency is +2 as no. of proton and no. of electron are same in an atom.
So, electronic configuration is 2,2
So, valency is +2.