How many unpaired electrons are there in Ni2 + (Z = 28)?

A 0
B 8
C 2
D 4

To determine the number of unpaired electrons in Ni^2+ (nickel ion with a +2 charge), let's first find the electron configuration of neutral nickel (Ni) and then adjust it for the +2 charge.

The electron configuration of neutral nickel (Ni) is: 1s^2 2s^2 2p^6 3s^2 3p^6 3d^8 4s^2.

When nickel loses two electrons to form Ni^2+, it loses them from its 4s and 3d orbitals. So, the electron configuration of Ni^2+ becomes: 1s^2 2s^2 2p^6 3s^2 3p^6 3d^8.

In the 3d subshell, there are 8 electrons. To determine if there are any unpaired electrons, we'll use Hund's rule, which states that electrons occupy orbitals of the same energy singly before filling them doubly.

So, in the 3d orbital of Ni^2+, there are no unpaired electrons because all the electrons are paired.

Thus, the correct answer is:

A) 0