Question

what is the relationship between electronegativity and bond type? Put another way, how could you predict whether a compound would be ionic or covalent if given a list of the elements’ electronegativities?

Answer 1

The greater the difference in electronegativity (ΔEN) between two atoms, the greater the degree in ionic character in the bond.

If you have a bond between atoms A and B (A-B),

ΔEN = |EN_A - EN_B|

The rules for the type of bond are:

• If ΔEN < 0.5, the bond is nonpolar covalent

• If 0.5 ≤ΔEN < 1.7, the bond is polar covalent

• If ΔEN ≥ 1.7, the bond is ionic

Examples:

C-H: ΔEN = |2.55 – 2.20| = 0.35; nonpolar covalent

C-F: ΔEN = |2.55 – 3.98| = 1.43; polar covalent

Na-F: ΔEN = |0.93 – 3.98| = 3.05; ionic