Question

valency of copper is 1 but when shell is configuration in shell k.l.m.n.so the valency is 3 because 2.8.8.8.3 so the outer most shell is 3 so that is valency

Answer 1

there are two types of copper one is cuprous it's valency is 1 and another one is cupric it's valency is 2
this is because of spdf
thanks