# How many unpaired electrons are in a iron atom?

Feb 20, 2017

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

#### Explanation:

The ground state configuration of Fe is

$\left[A r\right] 4 {s}^{2} 3 {d}^{6}$

The $4 s$ electrons are paired, and with six electrons in the $3 d$ 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 $3 d$ 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.)