Question

Why zinc metal and ${Zn}^{++}$ ions are diamagnetic?

Answer 1

Diamagnetic means the orbitals are fully paired ie. have paired electron and no unpaired electron. So in Zn whose electronic configuration is: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{1}0$

So here the d orbital is fully paired and no unpaired electron is present.

Similarly $Z{n}^{2+}$ looses 2 electrons from the 4s orbital. So again you will get fully filled 3d orbital and no unpaired electrons. Hence $Zn$ and $Z{n}^{2+}$ are Diamagnetic.