# Why is FeCl3 a Lewis acid?

Feb 6, 2014

${\text{FeCl}}_{3}$ is a Lewis acid because it can accept an electron pair from a Lewis base.

#### Explanation:

$\text{Fe}$ is in Period 4 of the Periodic Table.

Its electron configuration is ${\text{[Ar]4s"^2"3d}}^{6}$. It has eight valence electrons.

In order to obtain a $\text{[Kr]}$configuration, it can add up to ten more electrons.

In ${\text{FeCl}}_{3}$, the three $\text{Cl}$ atoms contribute three more valence electrons to make a total of 11.

The $\text{Fe}$ atom can easily accept more electrons from an electron-pair donor.

For example,

$\text{Cl"^"-" + "FeCl"_3 → "FeCl"_4^"-}$

Since ${\text{FeCl}}_{3}$can accept electrons, ${\text{FeCl}}_{3}$ is a Lewis acid.