Example 8

Solution

a) The Lewis diagram

shows that Be is electron deficient. Therefore BeCl₂(g) is a Lewis acid. Because of the lone pairs on the Cl atoms, BeCl₂ can also act as a Lewis base, but Cl is rather electronegative and reluctant to donate electrons, so the Lewis base strength of BeCl₂ is less than the Lewis acid strength.

b) There are lone pairs on O in CH₃OH, and so it can serve as a Lewis base.

c) The S atom in SO₂ can accept an extra pair of electrons, and so SO₂ is a Lewis acid. The O atoms have lone pairs but are only weakly basic for the same reason as the Cl atoms in part (a).

d) Although there are lone pairs on the F atoms, the high electronegativity of F prevents them from being donated to form coordinate covalent bonds. Consequently CF₄ has essentially no Lewis-base character.