Electronegativity
Electronegativity is how strongly an atom pulls shared electrons toward itself in a bond. It rises across a period and falls down a group. Fluorine is the highest on the Pauling scale, at 4.0.
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Analogy
A tug of war over a shared rope. The atom with the stronger pull gets the rope closer.
Example
F 4.0 O 3.5Cl 3.0 C 2.5H 2.1 Na 0.9Na–Cl gap = 2.1 (ionic)
In practice
The gap in electronegativity between two atoms tells you if their bond is ionic, polar covalent or nonpolar covalent.
Practice
Flashcards
- Which element has the highest electronegativity?Fluorine, at 4.0 on the Pauling scale.
Questions people ask
How is electronegativity different from electron affinity?
Electron affinity is the energy change when a lone gas atom gains an electron. Electronegativity describes how strongly an atom attracts shared electrons while it is bonded to another atom. One is measured on a single atom, the other is a bonding tendency, so they are related but not the same.
What electronegativity difference makes a bond ionic?
There is no sharp line, but a difference above about 1.7 to 2.0 is usually treated as ionic. Between about 0.4 and 1.7 the bond is polar covalent. Below 0.4 it is nearly nonpolar. Real bonds sit on a smooth scale, so these cut-offs are only guides.