What is the electronegativity gap?
Pick the two elements of a bond. The calculator shows each element’s Pauling electronegativity, the difference ΔEN, the bond type that difference suggests, and which atom takes the partial negative charge.
- Electronegativity difference
- ΔEN = 1.0: polar covalent
The electronegativity difference between C (2.5) and O (3.5) is 1.0: polar covalent.
- ΔEN
- 1.0
- Bond type (ΔEN guide)
- polar covalent
- First element’s EN
- 2.5
- Second element’s EN
- 3.5
- Partial charges
- O pulls the shared electrons: Cδ+ and Oδ−
- Bond
- C (2.5) and O (3.5)
Electronegativity difference: ΔEN = 1.0: polar covalent. The electronegativity difference between C (2.5) and O (3.5) is 1.0: polar covalent.
How to calculate
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.
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.
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.
- 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
Each example is checked against the calculator on every build.
- First element Carbon (C) 2.5, Second element Oxygen (O) 3.5 gives ΔEN 1, Bond type (ΔEN guide) polar covalent, Partial charges 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−
- First element Carbon (C) 2.5, Second element Hydrogen (H) 2.1 gives ΔEN 0.4, Bond type (ΔEN guide) polar covalent, Partial charges 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+
- First element Oxygen (O) 3.5, Second element Hydrogen (H) 2.1 gives ΔEN 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
- First element Sodium (Na) 0.9, Second element Chlorine (Cl) 3.0 gives ΔEN 2.1, Bond type (ΔEN guide) 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)
- First element Silicon (Si) 1.8, Second element Oxygen (O) 3.5 gives ΔEN 1.7, Bond type (ΔEN guide) 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
- First element Carbon (C) 2.5, Second element Carbon (C) 2.5 gives ΔEN 0, Bond type (ΔEN guide) 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
How it works
Values. Pauling electronegativities to one decimal, as printed in OpenStax Chemistry 2e, Figure 7.6:
| Period | Elements |
|---|---|
| 1 | H 2.1 |
| 2 | Li 1.0, Be 1.5, B 2.0, C 2.5, N 3.0, O 3.5, F 4.0 |
| 3 | Na 0.9, Mg 1.2, Al 1.5, Si 1.8, P 2.1, S 2.5, Cl 3.0 |
| 4 | K 0.8, Ca 1.0, Sc 1.3, Ti 1.5, V 1.6, Cr 1.6, Mn 1.5, Fe 1.8, Co 1.9, Ni 1.9, Cu 1.9, Zn 1.6, Ga 1.6, Ge 1.8, As 2.0, Se 2.4, Br 2.8 |
| 5 | Rb 0.8, Sr 1.0, Y 1.2, Zr 1.4, Nb 1.6, Mo 1.8, Tc 1.9, Ru 2.2, Rh 2.2, Pd 2.2, Ag 1.9, Cd 1.7, In 1.7, Sn 1.8, Sb 1.9, Te 2.1, I 2.5 |
| 6 | Cs 0.7, Ba 0.9, Hf 1.3, Ta 1.5, W 1.7, Re 1.9, Os 2.2, Ir 2.2, Pt 2.2, Au 2.4, Hg 1.9, Tl 1.8, Pb 1.9, Bi 1.9, Po 2.0, At 2.2 |
| 7 | Fr 0.7, Ra 0.9, Ac 1.1, Th 1.3, Pa 1.4, U 1.4 |
The figure gives no value for the noble gases, a range of 1.0 to 1.2 for La to Lu, and 1.4 to 1.3 for Np to No; those elements are not offered.
Difference. ΔEN = |EN(first) − EN(second)|, exact to one decimal.
Bond type (OpenStax Figure 7.8, a rough guide).
- ΔEN below 0.4: pure covalent (nonpolar).
- ΔEN from 0.4 to 1.8, both ends included: polar covalent.
- ΔEN above 1.8: ionic.
Partial charges. When the values differ, the more electronegative atom takes the partial negative charge (δ−) and the other the partial positive charge (δ+). Equal values give no partial charges.
Worked examples by hand
C–O (OpenStax Example 7.3). 3.5 − 2.5 = 1.0: polar covalent, with Cδ+ and Oδ−.
C–H. 2.5 − 2.1 = 0.4: at the lower end of polar covalent; carbon is δ−, hydrogen δ+.
O–H. 3.5 − 2.1 = 1.4: polar covalent.
Na–Cl. 3.0 − 0.9 = 2.1: above 1.8, ionic.
Si–O. 3.5 − 1.8 = 1.7: polar covalent.
C–C. 2.5 − 2.5 = 0.0: pure covalent.
Other questions people ask
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.