hydrogen ion

A hydrogen ion is a hydrogen atom that has lost or gained an electron, and in consequence has a charge. The positive hydrogen ion (H+), having lost its only electron, consists of just a proton.


Chemically free hydrogen ions are rarely formed and dissociation to H+ occurs only when the resultant ion can be complexed. Thus hydrogen chloride (HCl) gas is undissociated but gives [H(H2O)n]+Cl- and [NH4]+Cl- with water or ammonia.