# What is the ionic bond formation of aluminum and chlorine?

Feb 2, 2014

Aluminum and chlorine form covalent bonds, not ionic bonds.

#### Explanation:

The $\text{Al-Cl}$ bond is polar covalent.

This is consistent with the fact that aluminum chloride changes directly from a solid to a gas at the relatively low temperature of 180 °C.

Al has three valence electrons.

$\text{Cl}$ has seven valence electrons.

$\text{Al}$ and $\text{Cl}$ must achieve their octets by sharing electrons.

${\text{AlCl}}_{3}$ is still electron deficient. The $\text{Al}$ has only six electrons in its valence shell.

Measurements show that the formula of the vapour is ${\text{Al"_2"Cl}}_{6}$.

It exists as a dimer (two molecules joined together) in which two electrons from one $\text{Cl}$ are shared with the $\text{Al}$ of the other ${\text{AlCl}}_{3}$ molecule to form a coordinate bond. In this way. all atoms gain an octet.

Energy is released when the two coordinate bonds are formed, so the dimer is more stable than two separate ${\text{AlCl}}_{3}$ molecules.