Question

Zn (30) : $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^2$
How to find valency of zinc by electronic configuration?

Answer 1

$Zn\left(30\right):1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}$

K shell can accomodate upto $-2$ electrons.

L shell can accomodate upto $-8$ electrons

M shell can accomodate upto $-18$ electrons

Now, total electrons in K,L and M shells $=2+8+18=28$

Remaining $2$ electrons can be lost to complete its octet thats why its valency will $2$