# Question #77ee9

Feb 13, 2017

Note that iron is NOT a main group element, and thus it does not really follow the octet rule.

#### Explanation:

For iron, $Z = 26$

The full electronic configuration of the iron atom is:

$1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 4 {s}^{2} 3 {d}^{6}$

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

As is standard for a transition metal, upon oxidation, the $4 s$ electrons are removed FIRST to give $\text{ferrous ion}$, $F {e}^{2 +}$:

$1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 3 {d}^{6}$

And further oxidation can occur to give $\text{ferric ion}$, $F {e}^{3 +}$:

$1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 3 {d}^{5}$.

In general, iron exhibits $F e \left(I I +\right)$ and $F e \left(I I I +\right)$ oxidation states......