In chemistry, a lyonium ion is the cation derived by the protonation of a solvent molecule. For example, a hydronium ion is formed from the protonation of water and CH
2 is the cation formed by the protonation of methanol. Lyate ion which is the anion formed by the deprotonation of a solvent molecule. These ions resulting from molecular autoionization contribute to the molar conductivity of protolytic solvents.