Hydrogen

Hydrogen is the chemical element with atomic number 1. Its atoms have one proton, and its most abundant isotope, protium, has no neutrons.

Protium: The most abundant hydrogen isotope, with one proton and no neutrons. This isotope matches the usual hydrogen atom described by the element’s simplest model.
Hydrogen oxidation: The loss of electrons by hydrogen, often producing hydrogen ions or water. Oxidation explains how hydrogen releases energy in cells, flames, and fuel cells.
Haber–Bosch process: An industrial process that synthesizes ammonia from nitrogen and hydrogen. It consumes large quantities of hydrogen to supply the nitrogen fertilizer industry.
Big Bang nucleosynthesis: The formation of the lightest atomic nuclei during the first minutes of the universe. It produced most primordial hydrogen nuclei along with helium and traces of other light elements.
Helium: The chemical element with atomic number 2, whose atoms contain two protons. The next element shows how adding one proton changes nuclear stability and chemical behavior.
Deuterium: A stable hydrogen isotope with one proton and one neutron. Its extra neutron changes hydrogen’s mass and enables heavy-water chemistry.
Hydrogen evolution reaction: An electrochemical reaction that produces molecular hydrogen from protons or water. This reaction forms H₂ in electrolysis and is a key step in water splitting.
Steam reforming: A process that reacts hydrocarbons with steam to produce hydrogen-rich synthesis gas. It is the leading industrial route for producing hydrogen from natural gas.
Stellar nucleosynthesis: The formation of atomic nuclei through nuclear reactions inside stars. Hydrogen fusion powers stars and initiates the chain that builds heavier elements.
Alkali metal: An element in Group 1, characterized by one valence electron and strong chemical reactivity. Hydrogen shares a single valence electron with this group but is not an alkali metal.

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