# What is the electronegativity gap?

Gives the Pauling electronegativity of two elements and the difference between them, with the bond type it suggests (pure covalent, polar covalent or ionic) and which atom takes the partial negative charge.

- Page: https://www.acalculator.org/chemistry/electronegativity-calculator
- JSON spec: https://www.acalculator.org/chemistry/electronegativity-calculator.json
- Version: 83af54dd5c95

## Default answer

Example with the default inputs (First element Carbon (C) 2.5, Second element Oxygen (O) 3.5): The electronegativity difference between C (2.5) and O (3.5) is 1.0: polar covalent.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| a | First element | The first atom of the bond. |
| b | Second element | The second atom of the bond. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| result | Electronegativity difference | ΔEN with the bond type it suggests. |
| difference | ΔEN | The absolute difference of the two Pauling electronegativities. |
| bond | Bond type (ΔEN guide) | Pure covalent below 0.4, polar covalent from 0.4 to 1.8, ionic above 1.8: a rough guide. |
| enA | First element’s EN | The first element’s Pauling value. |
| enB | Second element’s EN | The second element’s Pauling value. |
| polarity | Partial charges | Which atom pulls the shared electrons and takes the partial negative charge (δ−). |
| pair | Bond | The two elements with their values. |

## Method

ΔEN = |EN(A) − EN(B)| with Pauling electronegativities (OpenStax Figure 7.6). Guide: ΔEN below 0.4 pure covalent, 0.4 to 1.8 polar covalent, above 1.8 ionic. The more electronegative atom takes the partial negative charge.

## Assumptions

- Pauling electronegativities to one decimal as OpenStax prints them; the noble gases, the lanthanides (given only as 1.0 to 1.2), the actinides after uranium (1.3 to 1.4) and the elements after them have no single value and are not listed.
- The bond type is a rough guide with many exceptions: H–F (1.9) is polar covalent and MnI₂ (1.0) is ionic.

## Worked examples

1. a = C, b = O gives difference = 1, bond = polar covalent, polarity = O pulls the shared electrons: Cδ+ and Oδ−. Source: OpenStax, Chemistry 2e, §7.2 Covalent Bonding (Figure 7.6 Pauling electronegativities; Figure 7.8 ΔEN guide), https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding, Example 7.3 Electronegativity and Bond Polarity: C–O, ΔEN = 1.0, Cδ+–Oδ−.
2. a = C, b = H gives difference = 0.4, bond = polar covalent, polarity = C pulls the shared electrons: Hδ+ and Cδ−. Source: OpenStax, Chemistry 2e, §7.2 Covalent Bonding (Figure 7.6 Pauling electronegativities; Figure 7.8 ΔEN guide), https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding, Example 7.3: C–H, ΔEN = 0.4, Cδ−–Hδ+.
3. a = O, b = H gives difference = 1.4. Source: OpenStax, Chemistry 2e, §7.2 Covalent Bonding (Figure 7.6 Pauling electronegativities; Figure 7.8 ΔEN guide), https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding, Example 7.3: O–H, ΔEN = 1.4.
4. a = Na, b = Cl gives difference = 2.1, bond = ionic. Source: OpenStax, Chemistry 2e, §7.2 Covalent Bonding (Figure 7.6 Pauling electronegativities; Figure 7.8 ΔEN guide), https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding, Electronegativity versus Bond Type: Na–Cl, 2.1 (ionic).
5. a = Si, b = O gives difference = 1.7, bond = polar covalent. Source: OpenStax, Chemistry 2e, §7.2 Covalent Bonding (Figure 7.6 Pauling electronegativities; Figure 7.8 ΔEN guide), https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding, Check Your Learning after Example 7.3: Si–O, ΔEN = 1.7.
6. a = C, b = C gives difference = 0, bond = pure covalent (nonpolar). Source: OpenStax, Chemistry 2e, §7.2 Covalent Bonding (Figure 7.6 Pauling electronegativities; Figure 7.8 ΔEN guide), https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding, Check Your Learning after Example 7.3: C–C, ΔEN = 0.0, nonpolar.

## FAQ

### What is electronegativity?

A measure of how strongly an atom attracts the electrons it shares in a bond. Linus Pauling set up the usual scale, a relative scale from 0 to 4 with no units. Fluorine is the most electronegative element at 4.0; values rise across a period and fall down a group.

### How do I find the electronegativity difference?

Look up both values and subtract the smaller from the larger. For a C–O bond, 3.5 − 2.5 = 1.0. The difference ΔEN is always 0 or more; which atom is more electronegative tells you the direction of the polarity.

### How can I tell if a bond is ionic or covalent?

OpenStax gives a rough guide: ΔEN below 0.4 is pure covalent, 0.4 to 1.8 polar covalent, and above 1.8 ionic. It has many exceptions: H–F has ΔEN 1.9 but is polar covalent, while MnI₂ (1.0) is ionic. Metal–nonmetal compounds are usually ionic whatever the difference.

### Which atom gets the partial negative charge?

The more electronegative one. It pulls the shared electrons toward itself and takes δ−, and the other atom takes δ+. In an O–H bond oxygen (3.5) is δ− and hydrogen (2.1) is δ+.

### Why do other tables give oxygen 3.44 instead of 3.5?

Pauling’s values were later refined to two decimals (oxygen 3.44, carbon 2.55, hydrogen 2.20). This page uses the one-decimal Pauling values printed in OpenStax Chemistry 2e, so its differences match the textbook’s worked examples. Near 0.4 or 1.8 the two tables can put a bond on different sides of the guide.

### Why are some elements missing?

OpenStax’s table gives no value for the noble gases, gives the lanthanides only as a range (1.0 to 1.2) and the actinides after uranium as 1.4 to 1.3, and stops at those. The page lists only the 71 elements with a single value.

## Sources

- OpenStax, Chemistry 2e, §7.2 Covalent Bonding: the definition of electronegativity, Figure 7.6 (Pauling electronegativity values, read from the figure), Figure 7.8 (ΔEN below 0.4 pure covalent, 0.4 to 1.8 polar covalent, above 1.8 ionic, a general guide with exceptions such as HF and MnI₂), Example 7.3 (C–H 0.4, C–O 1.0, O–H 1.4) and its Check Your Learning (C–C 0.0, Si–O 1.7), and H–Cl 0.9, Na–Cl 2.1. https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding (retrieved 2026-10-19)
- Wikipedia, Electronegativities of the elements (data page): the revised two-decimal Pauling values (H 2.20, C 2.55, O 3.44) after Allred (1961). https://en.wikipedia.org/wiki/Electronegativities_of_the_elements_(data_page) (retrieved 2026-10-19)