How many unpaired electrons are present in a ground state gaseous${\mathrm{Ni}}^{2+}$ ion?

The atomic number of Ni is 28. Its electronic configuration is$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^8$.

Now, the electronic configuration of ${\mathrm{Ni}}^{2+}$(losing two-electron ) is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^8$

${\mathrm{Ni}}^{2+}$ has 8 electrons in its outermost shell, out of which there are six paired electrons and two unpaired electrons.

Therefore, the unpaired electrons present in a ground state gaseous  ${\mathrm{Ni}}^{2+}$ is 2