# What factors determine acid strength?

Acid strength is determined by the amount of that acid that actually ionizes. Acids are molecular covalent compounds which you don't expect to ionize (release an ${H}^{+}$ and leave behind the conjugate base, or $C {l}^{-}$ for example).
The strongest acids ionize 100%. There are 6 that most consider to be the "STRONG" acids: HCl, HI, HBr, HNO_3$, {H}_{2} S {O}_{4}$ and HClO_4#. These split apart 100%.