Question

Why is `ZnCl_2` a lewis acid?

Answer 1

`ZnCl_2` is a Lewis acid because it can accept an electron pair from a Lewis base.

A Lewis acid is a molecule that can accept an electron pair and a Lewis base is a molecule that can donate and electron pair. When a Lewis base combines with a Lewis acid an adduct is formed with a coordinate covalent bond.

A zinc atom has the electron configuration [Ar]4s²3d¹⁰.

Using only the s electrons, VSEPR theory predicts ZnCl₂ to have a linear AX₂ structure with only four valence shell electrons. This is an incomplete octet. Thus, ZnCl₂ will behave as a Lewis acid in an attempt to acquire more valence electrons.

In many of its compounds, Zn has eight or twelve valence electrons.