Why can sulfuric acid form both hydrogen sulfate salts and sulfate salts?

Sulfuric acid (${\text{H}}_2{\text{SO}}_4$) can form two series of salts—hydrogen sulfates (${\text{HSO}}_4^{-}$) and sulfates (${\text{SO}}_4^{2-}$)—because it is a diprotic acid.123

This means that each molecule of sulfuric acid contains two hydrogen atoms bonded to oxygen atoms, which it can donate as hydrogen ions (${\text{H}}^{+}$) in two distinct ionization stages.123

• First Ionization: In aqueous solution, the loss of the first hydrogen ion is essentially complete, resulting in the formation of the hydrogen sulfate ion (${\text{HSO}}_4^{-}$).23
• Second Ionization: The second hydrogen ion is released partially, producing the sulfate ion (${\text{SO}}_4^{2-}$).23

Because the acid can donate these ions in sequence, it is capable of forming salts corresponding to both the partial and complete removal of its hydrogen atoms.23