Textbook Question 2A19)

[Ayesha Aslam-Mir 3C]

Why does the Ni 2+ion have two unpaired electrons?

[Siwa Hwang 3G]

Electron configuration of Ni 2+ is [Ar] 3d8. Therefore, there are 3 electron pairs and 2 unpaired single electrons.

[Valerie Tran 2B]

To figure out the number of unpaired electrons predicted for the ground-state configuration of an atom, just find electron configuration and use Hund's rule to determine how many orbitals in the subshells have only one electron.

So for Ni 2+, the electron config: [Ar]3d^8. Since the d subshell has 5 orbitals and there are 8 electrons for 3d, which means two electrons in the first orbital, two electrons in the second orbital, two electrons in the third orbital and only one electron in the fourth and fifth orbital leaving two unpaired electrons.

Basically, you have put one electron in each subshell before you can double up so each orbital gets 1 electron leaving 3 left so you go back and keep adding until you use 8 electrons which leaves the last 2 orbitals without a pair.