Why is FeCl3 a Lewis acid?

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Answer 1 · 2014-02-06T01:25:10

#"FeCl"_3# is a Lewis acid because it can accept an electron pair from a Lewis base.

#"Fe"# is in Period 4 of the Periodic Table.

Its electron configuration is #"[Ar]4s"^2"3d"^6#. It has eight valence electrons.

In order to obtain a #"[Kr]" #configuration, it can add up to ten more electrons.

In #"FeCl"_3#, the three #"Cl"# atoms contribute three more valence electrons to make a total of 11.

The #"Fe"# atom can easily accept more electrons from an electron-pair donor.

For example,

#"Cl"^"-" + "FeCl"_3 → "FeCl"_4^"-"#

Since #"FeCl"_3#can accept electrons, #"FeCl"_3# is a Lewis acid.