Worked Example: Classify the H–Cl bond
Given: χ(H) = 2.2, χ(Cl) = 3.2
1. Calculate Δχ: |3.2 − 2.2| = 1.0
2. Classify: Δχ = 1.0 falls in the range 0.5–1.7 → Polar Covalent.
3. Dipole direction: Cl is more electronegative → δ⁻ on Cl, δ⁺ on H.
Answer: H–Cl is a polar covalent bond. The dipole points from H → Cl.
Think About It
The H–F bond has Δχ = 1.8. Should we classify it as ionic or polar covalent?
It sits right on the boundary. In practice, HF is considered polar covalent because fluorine is a non-metal. The Δχ thresholds are guidelines, not rigid rules — we must also consider the bonding continuum and the nature of the atoms involved.