Nascent hydrogen

In chemistry, nascent hydrogen is non-ionised, monatomic hydrogen (H⁰) that exists transiently after the reduction of hydrogen ions. Generated in situ usually by the reaction of zinc with an acid, it is a much more effective reducing agent than ordinary gaseous hydrogen, but can also cause embrittlement of metals.

Nascent hydrogen can reduce nitrites to ammonia, or arsenic to arsine even when cold.