What is the ionic bond formation of aluminum and chlorine?

1 Answer
Feb 2, 2014

Aluminum and chlorine form covalent bonds, not ionic bonds.

Explanation:

The "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.

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"Cl" has seven valence electrons.

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"Al" and "Cl" must achieve their octets by sharing electrons.

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"AlCl"_3 is still electron deficient. The "Al" has only six electrons in its valence shell.

Measurements show that the formula of the vapour is "Al"_2"Cl"_6.

It exists as a dimer (two molecules joined together) in which two electrons from one "Cl" are shared with the "Al" of the other "AlCl"_3 molecule to form a coordinate bond. In this way. all atoms gain an octet.

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Energy is released when the two coordinate bonds are formed, so the dimer is more stable than two separate "AlCl"_3 molecules.