Why is the valency of metal potassium is +1 and of the non-metal chlorine is -1 - Chemistry -

Question

Why is the valency of metal potassium is +1 and of the non-metal
chlorine is -1

Pankaj Singh · Accepted Answer

Electronic configuration of Potassium is 2,8,1
It has only one electron in its valence shell so it can complete
its octet very easily by removing one and only electron from the
valence shell Removal of one electron will produce +1 charge on it
and thus the valency of K is +1
Electronic configuration of Chlorine is 2,8,7
It needs only one electron in its valence shell to complete is
octet so it accept one electron in its valence shell Addition of
one electron will produce -1 charge on it and thus the valency of
Cl is -1

Why is the valency of metal potassium is +1 and of the non-metal chlorine is -1.