Question

State why the valency of the metals potassium is +1 and of of the non metal chlorine -1

Answer 1

metals lose electrons to be stable and nonmetals gain electrons to be stable that's why the valency of metal Potassium is + 1 and nonmetal chlorine is -1 .
hope it helps you.

Answer 2

Electronic configuration of potassium is -
2,8,8, 1

Whereas electronic configuration of chlorine is 2, 8, 7

Hence for completing their respective octate they lose and gain 1 electron respectively