What this calculator does
Electronegativity measures how strongly an atom pulls shared electrons toward itself when it forms a bond. This calculator holds the standard Pauling-scale electronegativity value for each of 21 commonly taught elements and reports the value for either one, plus the difference between two chosen elements, which is the figure actually used to judge what kind of bond forms between them.
The two elements do not need to be different: choosing the same element twice returns a difference of zero, which is the expected result for a bond between two atoms of one element, such as the O-O bond in O2, where no electron is pulled preferentially either way.
The formula
Electronegativity difference is the absolute value of one element's Pauling value minus the other's, so the order the two elements are chosen in does not change the result. A difference under about 0.4 indicates a nonpolar covalent bond, where electrons are shared close to evenly; a difference roughly between 0.4 and 1.7 indicates a polar covalent bond, where electrons sit closer to the more electronegative atom; and a difference above about 1.7 indicates a bond that behaves as mostly ionic, where an electron effectively transfers rather than being shared.
| Term | Meaning |
|---|---|
| Electronegativity | A dimensionless number on the Pauling scale describing how strongly an atom attracts shared electrons in a bond. Fluorine, at 3.98, is the most electronegative element; caesium and francium sit at the low end. |
| Pauling scale | The most widely used electronegativity scale, developed by Linus Pauling from measured bond energies, running roughly from 0.7 to 4.0 across the periodic table. |
| Bond polarity | How unevenly a shared pair of electrons sits between two bonded atoms. Larger electronegativity differences produce more polar, more ionic-leaning bonds. |
The inputs explained
| Field | What to enter |
|---|---|
| Element A | The first element in the comparison. |
| Element B | The second element in the comparison. Difference is calculated regardless of which order the two are chosen in. |
When to use it
Predicting whether a bond is covalent or ionic
Comparing two elements' electronegativity values before drawing a Lewis structure or predicting molecular polarity is a standard first step in introductory chemistry.
Explaining why water is a polar molecule
Oxygen (3.44) and hydrogen (2.20) differ by 1.24, enough to pull shared electrons noticeably toward oxygen, which is the underlying reason water molecules are polar and why water dissolves so many other substances.
Checking a textbook table without paging through the periodic table
Looking up two specific values to settle a homework question or check working is often faster than searching a printed periodic table for the same two figures.
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 does carbon's bond character change with different partners?
Carbon (electronegativity 2.55) compared against a spread of common bonding partners.
| Element B | Electronegativity difference (Δχ) | Likely bond character |
|---|---|---|
| Hydrogen | 0.35 | nonpolar covalent |
| Nitrogen | 0.49 | polar covalent |
| Oxygen | 0.89 | polar covalent |
| Fluorine | 1.43 | polar covalent |
| Chlorine | 0.61 | polar covalent |
| Sodium | 1.62 | polar covalent |
Questions
What is the most electronegative element?
Fluorine, at 3.98 on the Pauling scale, is the most electronegative element on the periodic table. It sits at the top right of the table, since electronegativity generally increases moving right and up across the periodic table.
What does a difference of zero mean?
A difference of zero means both atoms pull on shared electrons equally, which happens for a bond between two atoms of the same element, such as the H-H bond in hydrogen gas. Electrons are shared exactly evenly in that case.
Are the exact cutoffs (0.4 and 1.7) strict rules?
No, they are commonly taught guidelines rather than hard boundaries. Real bonds sit on a continuous spectrum from purely covalent to purely ionic, and the cutoffs are a convenient way to categorise where a given bond falls on that spectrum, not a precise physical threshold.
Why do metals generally have low electronegativity?
Metal atoms hold their outer electrons relatively loosely and readily lose them rather than pulling in more, which is the same underlying property that makes metals good electrical conductors and explains their generally low electronegativity values.
To work out the resulting percentage ionic character of a bond rather than just its category, see percent ionic character. For the actual proton, neutron and electron counts an ion, see atom composition.