Fluoronium (systematically named fluoranium, and μ-fluorido-dihydrogen(1+)) is an inorganic cation with the chemical formula H2F+ (also written [H2F]+). It contributes no colour to fluoronium salts. It is a very strong acid, and dilute fluoronium solutions are corrosive and can attack the skin. It can be formed by protonation or self-ionic dissociation of hydrogen fluoride: HF + H+ → H2F+ or 3HF ⇌ H2F+ + HF−2 The fluoronium ion is isoelectronic with water and the amide ion.