3.1.1—Electronegativity

Electronegativity is the power of an atom to attract the bonding pair of electrons towards itself in a covalent bond. It is a comparative property of bonded atoms, not the charge on an isolated ion and not the energy needed to remove an electron.

When two bonded atoms have different electronegativities, the bonding electrons are attracted more strongly towards the atom with the higher value. This unequal attraction can make the bond polar; similar values indicate more equal sharing.

Use electronegativity to describe the direction and relative strength of attraction within a bond. Periodic trends and the factors that cause them belong to the neighbouring objectives; numerical differences used to predict ionic or covalent bonding also belong to the later application card.

Do not treat electronegativity as a fixed whole-atom charge, confuse it with first ionisation energy, or infer the polarity of an entire molecule from one bond without considering the other bonds and molecular shape. This card establishes the definition only.