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Bond Polarity Calculator

Chemistry

Classify a bond from Pauling electronegativities, check whether a molecule is polar from its VSEPR shape, or work out ionic character from a measured dipole moment.

Textbooks draw these lines in different places. Use your course's values. 1.7 is popular because Pauling's curve gives ≈ 50 % ionic character there.

Hydrogen: χ = 2.20

Chlorine: χ = 3.16

Δχ doesn't depend on bond order: C–O, C=O and C≡O all have Δχ = 0.89.

δ+ H–Cl δ−

Polar covalent

Δχ = |3.16 − 2.20| = 0.96

χ(H)

2.20

χ(Cl)

3.16

Δχ

0.96

Bond type

Polar covalent

δ− atom

Cl (Chlorine)

Pauling % ionic (estimate)

20.6 %

Hannay–Smyth % ionic (estimate)

18.6 %

Convention

0.4 / 1.7

These are empirical fits. Dipole mode shows the measured value for diatomics you can check.

Bond sketch

Hχ 2.20δ+Clχ 3.16δ−

Arrow uses the chemistry convention (points to δ−). The physics dipole vector points the other way. Cloud offset is schematic.

Where the two atoms sit on the Pauling scale

Faint ticks mark every element with a value. F sits alone at the top; most metals crowd into a narrow band.

1.01.52.02.53.03.54.0CsCOFΔχ = 0.96HCl

Ionic character against Δχ

Pauling (solid) and Hannay–Smyth (dashed) estimates, with the class bands of the 0.4 / 1.7 convention.

Bands, left to right:

Nonpolar (Δχ < 0.40)

Polar covalent

Ionic, metal + non-metal (Δχ ≥ 1.70)

Hollow markers are diatomics measured from their dipole moments. They scatter around both curves (LiH 77 % at Δχ 1.22, HF 41.5 % at 1.78), so treat the curves as rough guides.

Compare bonds

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About This Tool

Bond Polarity Calculator – Electronegativity, Ionic Character and Molecular Dipoles

Electronegativity measures how strongly an atom pulls shared electrons toward itself in a bond. When two bonded atoms differ in electronegativity, the electron cloud shifts toward the more electronegative one. That end carries a partial negative charge (δ−) and the other a partial positive charge (δ+). This bond polarity calculator finds the electronegativity difference Δχ for any pair of elements, names the bond type, estimates the percent ionic character, checks whether a whole molecule is polar, and works out ionic character from a measured dipole moment.

Where Pauling's numbers come from

Linus Pauling noticed that a bond between two different atoms is usually stronger than the average of the two like-atom bonds. He took that extra stability as a measure of the charge shift:

Δ = D(A–B) − ½[D(A–A) + D(B–B)] |χA − χB| = 0.102 · √Δ (Δ in kJ/mol)

For HCl, with bond energies of 431, 436 and 242 kJ/mol, Δ = 431 − ½(436 + 242) = 92 kJ/mol, so Δχ = 0.102 × √92 ≈ 0.98. The tabulated difference is 0.96. The calculator uses the revised Pauling values (Allred, 1961) for the whole periodic table and flags the handful the sources list as estimates.

Periodic trends

Electronegativity rises across a period and falls down a group. Across a period the effective nuclear charge grows while the atom shrinks, so the nucleus holds bonding electrons more tightly. Down a group the valence shell sits farther out and is better shielded. Fluorine (3.98) is the most electronegative element, and caesium (0.79) is among the least. The scale strip in Bond mode shows how most metals crowd into a narrow band between about 0.8 and 2.

A continuum, not three boxes

Bonds run smoothly from nonpolar covalent (equal sharing, as in Cl₂) through polar covalent (HCl, H₂O) to ionic (NaCl). The cut-offs are conventions. A popular one puts nonpolar below Δχ = 0.4 and ionic at 1.7 or more, but 1.8 and 2.0 are also common. Bond mode also checks the element types: two non-metals always make a covalent bond, however large Δχ is, and two metals form a metallic bond in the bulk.

Pick your course's convention
Switch between 0.4 / 1.7, 0.4 / 1.8, 0.5 / 2.0 or your own values at the top of the page. The choice is remembered, and it drives both Bond mode and the bond table in Molecule mode.

Two formulas for % ionic character

Pauling's estimate is %IC = 100 × (1 − e^(−Δχ²/4)). It gives about 50 % at Δχ = 1.7, which is why that line became the textbook boundary. The Hannay–Smyth fit, %IC = 16·Δχ + 3.5·Δχ², gives lower values for most bonds. Both are empirical. Dividing a diatomic molecule's measured dipole moment by e × r, the dipole of a full charge transfer, gives a measured ionic character. HCl comes out at 18.1 %, close to the formulas, but LiH (77 %) and HF (41.5 %) sit well away from them, as the chart shows.

Molecular polarity is a symmetry question

A molecule can contain polar bonds and still have no dipole. In linear CO₂ the two C=O dipoles point in opposite directions and cancel, while bent H₂O keeps a net dipole of 1.85 D. Molecule mode takes the shape from the VSEPR predictor and tests whether each set of identical bonds, and the lone pairs, sits symmetrically around the central atom. NH₃ and NF₃ have the same trigonal pyramidal shape. In NH₃ the bond dipoles point toward N and add to the lone pair, giving 1.47 D. In NF₃ they point toward F, against the lone pair, and the molecule measures only 0.23 D.

Exceptions worth knowing

  • HF has Δχ = 1.78 but is a molecular gas, not a salt: a very polar covalent bond.
  • CO has Δχ = 0.89, yet its tiny 0.11 D dipole has carbon at the negative end.
  • LiH and the other saline hydrides are ionic solids containing H⁻, although Δχ is only about 1.2.
  • CsAu is a real salt made of two metals, with gold as the auride anion Au⁻.

Other electronegativity scales

Mulliken defined electronegativity as the average of the ionization energy and the electron affinity. Allred and Rochow based theirs on the electrostatic force of the effective nuclear charge at the covalent radius, and Allen used the average energy of the valence electrons in the free atom. The scales broadly agree on the order of the elements but differ in detail. This calculator uses only the Pauling scale, which most general chemistry courses teach.

Frequently Asked Questions

Is the Bond Polarity Calculator free?

Yes, Bond Polarity Calculator is totally free :)

Can I use the Bond Polarity Calculator offline?

Yes, you can install the webapp as PWA.

Is it safe to use Bond Polarity Calculator?

Yes, any data related to Bond Polarity Calculator only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

What electronegativity difference makes a bond polar or ionic?

There is no single rule. A common convention calls a bond nonpolar below Δχ = 0.4, polar covalent from 0.4 to 1.7 and ionic from 1.7 up, but some courses use 1.8 or 2.0. The 1.7 line is popular because Pauling's formula gives about 50 % ionic character there, so this calculator lets you pick your course's cut-offs.

Why is HF called polar covalent when its Δχ is above 1.7?

Hydrogen and fluorine are both non-metals, and they form a molecular gas made of separate HF molecules, not a salt. Its measured dipole moment corresponds to only about 41 % ionic character, so the bond is very polar but still covalent.

How is percent ionic character calculated?

Pauling's formula estimates it as 100 × (1 − e^(−Δχ²/4)), and the Hannay–Smyth formula as 16·Δχ + 3.5·Δχ². For a diatomic molecule you can also measure it: divide the observed dipole moment by the dipole a full ±e charge would give at the bond length, e × r.

Can a molecule with polar bonds be nonpolar?

Yes. In CO₂, BF₃ and CCl₄ every bond is polar, but identical bonds point symmetrically around the central atom, so their dipoles add to zero. A molecule is polar only when its shape or its mix of outer atoms leaves a net dipole.

Why is NF₃ so much less polar than NH₃?

Both are trigonal pyramidal with one lone pair on nitrogen. In NH₃ the N–H bond dipoles point toward nitrogen and add to the lone pair's dipole, giving 1.47 D. In NF₃ the N–F dipoles point toward the fluorines, against the lone pair, so they largely cancel and the molecule measures only 0.23 D.

Which electronegativity scale does this calculator use?

It uses the revised Pauling values (Allred, 1961) as tabulated in the CRC Handbook, and marks the few that the sources list as estimates. Other scales such as Mulliken, Allred–Rochow and Allen give slightly different numbers, so check which one your textbook uses.