Percent Ionic Character Calculator
Ionic character of a bond from the electronegativity difference (Pauling’s equation) or from the measured dipole moment and bond length — with the bond type and the Hannay–Smyth estimate.
How it works
% ionic = 100·[1 − exp(−0.25·Δχ²)] (Pauling); ≈ 16Δχ + 3.5Δχ² (Hannay–Smyth); = 100 × μ_measured ÷ (e·r)
No bond is purely ionic or covalent; electronegativity difference sets where it sits. Pauling’s exponential relation gives 50% ionic character at Δχ ≈ 1.7, the conventional covalent/ionic boundary. The dipole-moment method compares the measured dipole with what full charge separation over the bond length would produce — for HF that is 41%, agreeing well with Pauling’s 43%. Percent ionic character predicts bond polarity, solubility trends and infrared intensities.
Worked example
H–F: Δχ = 1.78 → Pauling 55%, Hannay–Smyth 40%; from μ = 1.83 D over 91.7 pm (μ_ionic = 4.40 D) → 41.6% — a strongly polar covalent bond.
Frequently asked questions
Which estimate is best?
The dipole method is measured; Pauling’s tends to overestimate for small differences and the Hannay–Smyth fit is closer to experiment for many diatomics.
Is NaCl 100% ionic?
Δχ = 2.23 gives 71% by Pauling — real “ionic” bonds still have substantial covalent character.
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This calculator is for educational purposes. Double-check important results before acting on them.