Skip to content
CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Polar covalent bond

A covalent bond in which the electrons are shared unequally, so the more electronegative atom carries a partial negative charge (δ−\delta^-) and the other a partial positive charge (δ+\delta^+). This course uses 0.4≤ΔEN<1.80.4 \leq \Delta\text{EN} < 1.8.

From nonpolar covalent to ionicBond type depends on the electronegativity difference ΔEN. Cl–Cl (ΔEN 0) shares electrons equally: nonpolar covalent. H–Cl (ΔEN ≈ 1.0) shares unequally: polar covalent. Na⁺Cl⁻ (ΔEN ≈ 2.1) transfers an electron: ionic. Course cut-offs: below 0.4 nonpolar, 1.8 and above ionic.ClClshared equallyHClδ+δ−shared unequallyNa⁺Cl⁻e⁻ transferred00.41.83nonpolarpolar covalentionicΔEN (electronegativity difference)

Polar covalent bonds lie between equal sharing and full electron transfer.

Example

C–O: ΔEN=3.44−2.55=0.89\Delta\text{EN} = 3.44 - 2.55 = 0.89, polar covalent, with δ−\delta^- on O and δ+\delta^+ on C.

See alsoPartial charge (δ+ / δ−)Bond dipoleElectronegativity difference (ΔEN)Nonpolar covalent bond