What this calculator does
No bond is purely ionic or purely covalent; they sit on a continuum, and electronegativity difference places a bond along it. A difference of 0.96 gives about 21% ionic character, which is firmly polar covalent.
The conventional dividing lines are rules of thumb rather than physics. A difference below about 0.4 is usually called nonpolar, 0.4 to 1.7 polar covalent, and above 1.7 ionic, which corresponds to roughly 50% ionic character. Caesium fluoride, the most extreme natural pair, reaches only about 92%.
The formula
The Pauling relationship gives ionic character as 100 times one minus the exponential of minus the squared half-difference in electronegativity. It is an empirical fit rather than a derivation, and it is best treated as a way of ordering bonds rather than as a precise physical quantity.
| Term | Meaning |
|---|---|
| Electronegativity | How strongly an atom attracts bonding electrons. Pauling scale runs from 0.79 to 3.98. |
| Δχ | The difference between the two electronegativities. |
| Polar covalent | Shared electrons unequally distributed, the middle of the continuum. |
| Pauling scale | The most common electronegativity scale, with fluorine set at 3.98. |
The inputs explained
| Field | What to enter |
|---|---|
| Electronegativity of atom A | Electronegativity of the first atom. Fluorine is 3.98, oxygen 3.44, chlorine 3.16, carbon 2.55, hydrogen 2.20. |
| Electronegativity of atom B | Electronegativity of the second atom. Order does not matter, since only the difference is used. |
When to use it
Classifying a bond
Deciding whether to treat a bond as ionic or covalent affects how a compound properties are predicted.
Predicting polarity
Bond polarity drives dipole moments, solubility and intermolecular forces.
Comparing across a series
Ranking the hydrogen halides or a set of oxides by ionic character shows a clear periodic trend.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How ionic is each bond?
A range of electronegativities paired with hydrogen.
| Electronegativity of atom A | Percent ionic character | Electronegativity difference Δχ | Bond character |
|---|---|---|---|
| χ = 2.2 | 0.000% | 0.00 | nonpolar covalent |
| χ = 2.55 | 3.02% | 0.35 | nonpolar covalent |
| χ = 3.16 | 20.6% | 0.96 | polar covalent |
| χ = 3.44 | 31.9% | 1.24 | polar covalent |
| χ = 3.98 | 54.7% | 1.78 | mostly ionic |
Questions
Is any bond 100% ionic?
No. Even caesium fluoride, the most electronegativity-mismatched pair of stable elements, reaches only about 92% by this relationship. Some electron density is always shared. Purely ionic bonding is an idealisation, useful for predicting properties but never exactly realised.
Where is the line between ionic and covalent?
Conventionally a difference of 1.7, which corresponds to about 50% ionic character. This is a teaching convention rather than a physical boundary, and compounds near it often show properties of both types. Treat it as a guide to expectations, not a classification rule.
Does this predict whether a compound conducts?
Only loosely. Conductivity in the molten state is the practical test for ionic bonding, and it correlates with high ionic character but not perfectly. Structure matters too: aluminium chloride has substantial ionic character yet forms molecular dimers and conducts poorly.
Which electronegativity scale should I use?
Pauling, since the relationship was fitted to it. Mulliken and Allred-Rochow scales give different numbers and would need their own calibration. Mixing scales within one calculation produces a meaningless difference.
For the covalent end described by orbitals, see the bond order calculator. For lattice energy of ionic solids, see the lattice energy calculator.