What is Electronegativity?
Electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons (or electron density) towards itself. The most commonly used scale for measuring this property is the Pauling scale, named after chemist Linus Pauling. Values on this scale generally range from 0.7 (Francium) to 4.0 (Fluorine).
Understanding Bond Types
By calculating the difference in electronegativity (ΔEN) between two atoms in a chemical bond, we can predict the nature of that bond. The electrons in a bond are not always shared equally; the atom with the higher electronegativity will pull the electrons closer.
| Difference (ΔEN) | Bond Type | Description |
|---|---|---|
| 0.0 – 0.4 | Nonpolar Covalent | Electrons are shared relatively equally. Example: C-H bonds. |
| 0.4 – 1.7 | Polar Covalent | Electrons are shared unequally, creating partial charges (dipoles). Example: H-Cl. |
| > 1.7 | Ionic | Electrons are transferred from one atom to the other. Example: Na-Cl. |
How to Calculate Electronegativity Difference
The formula to determine the difference is simple absolute subtraction:
ΔEN = |EN1 – EN2|
Where EN1 and EN2 are the Pauling electronegativity values of the two atoms involved in the bond.
Example Calculation
Let's look at water (H2O), specifically the bond between Oxygen and Hydrogen:
- Oxygen (O) Electronegativity: 3.44
- Hydrogen (H) Electronegativity: 2.20
- Calculation: |3.44 – 2.20| = 1.24
Since 1.24 falls between 0.4 and 1.7, the bond is considered Polar Covalent.
Percentage Ionic Character
No bond is 100% ionic or 100% covalent (except bonds between identical atoms). This calculator estimates the percentage of ionic character using the Pauling equation:
% Ionic Character = 100 × (1 – e-(ΔEN2/4))
As the difference in electronegativity increases, the ionic character of the bond increases.