Oxoacid
An acid in which the ionisable hydrogen is attached to oxygen, which in turn is bonded to a central atom.
Formula / equation
HₙXOₘ
Unit
Dimensionless
In depth
For a given central element, acid strength rises sharply with the number of terminal oxygen atoms, because each one withdraws electron density and delocalises the negative charge of the conjugate base. Strength also increases with the electronegativity of the central atom.
Examples in the real world
HClO (pKa 7.5), HClO₂ (2.0), HClO₃ (−1) and HClO₄ (−8) show the trend over fifteen orders of magnitude.