How many unpaired electrons are in a iron atom?

1 Answer
Feb 20, 2017

There are four unpaired electrons in the 3d subshell of iron.

Explanation:

The ground state configuration of Fe is

[Ar]4s23d6

The 4s electrons are paired, and with six electrons in the 3d subsell, Hund's rule tells us these will consist of one pair and four single, unpaired electrons.

(If you are not familiar with Hund's rule, it states that when electrons populate a set of orbitals having identical energy - such as the five 3d orbitals - they do so by placing one electron in each orbital until all the orbitals are half-filled, then the electrons start to form pairs.)