Polarising Power
The ability of a cation to distort the electron cloud of a neighbouring anion.
Formula / equation
∝ charge / radius²
Unit
Dimensionless
In depth
Polarising power rises with charge density, so small, highly charged cations such as Al³⁺ and Be²⁺ are strongly polarising. High polarising power introduces covalent character, lowers melting points, increases solubility in organic solvents and makes the hydrated cation acidic in water.
Examples in the real world
Be²⁺ polarises so strongly that BeCl₂ is a covalent chain polymer; Al³⁺ makes AlCl₃ solutions distinctly acidic.