Nascent hydrogen is claimed to non-ionised, monatomic hydrogen (formula: H), which is claimed to exist transiently but long enough to effect chemical reactions. According to one claim, nascent hydrogen is generated in situ usually by the reaction of zinc with an acid, or by electrolysis at the cathode. Being monoatomic, H atoms are much more reactive and thus much more effective reducing agent than ordinary diatomic H₂, but again the key question is whether H atoms exist in any chemically meaningful way under the conditions claimed. The concept is more popular in engineering and in older literature on catalysis. “Multivalent” redirects here. ... In physics and chemistry, monatomic is a combination of the words mono and atomic, and means single atom. ... This article is about the chemistry of hydrogen. ... In situ is a Latin phrase meaning in the place. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... Acidity redirects here. ... It has been suggested that Electrolytic process be merged into this article or section. ... Diagram of a copper cathode in a Daniells cell. ... A reducing agent (also called a reductant or reducer) is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. ...

High energy and highly reactive nascent hydrogen atoms form and exist only temporarily, transiently, and in absence of anything to react with, they irreversibly react with each other to combine to H₂.

Nascent hydrogen is claimed to reduce nitrites to ammonia, or arsenic to arsine even under mild conditions. Detailed scrutiny of such claims usually points alternative pathways, not H atoms. // Definition The nitrite ion is NO2−. A nitrite compound is one that contains this group, either an ionic compound, or an analogous covalent one. ... Ammonia is a compound with the formula NH3. ... General Name, Symbol, Number arsenic, As, 33 Chemical series metalloids Group, Period, Block 15, 4, p Appearance metallic gray Atomic mass 74. ... Arsine, the simplest compound of arsenic, is AsH3. ...

Notes:

Occasionally, chemisorbed hydrogen chemisorbed on metal surfaces is referred to as "nascent", although this terminology is fading with time. Other views hold that such chemisorbed hydrogen is "a bit less reactive than nascent hydrogen because of the bonds provided by the catalyst metal surface." Also, such catalyst provided atoms are not called nascent hydrogen, because they don't need to be captured and reacted in their instanteneous, temporary, "just generated" state, because the catalyst is able to reversibly generate them from the hydrogen gas supply at any time.

Nascent hydrogen refers to is "room temperature atomic hydrogen." Of course hydrogen atoms can also form at temperatures severe enough to provide the activation energy needed to rupture H₂ into atoms. At room temperature high energy molecular hydrogen can also be generated with electromagnetic irradiation providing the "right energy" to dissociation:

H₂ + hʋ(photon) → 2 H

Although not as efficiently as by reaction or electrolysis, because of quantum yield issues - basically not all photons get absorbed to create a reaction, and the majority get wasted to simply generate heat, it is claimed. The word light is defined here as electromagnetic radiation of any wavelength; thus, X-rays, gamma rays, ultraviolet light, microwaves, radio waves, and visible light are all forms of light. ... The Quantum Yield of a radiation-induced process is the number of times that a defined event (usually a chemical reaction step) occurs per photon absorbed by the system. ...