hydrogen1

Hydrogen-1, commonly referred to as protium, is the most abundant isotope of hydrogen. Its nucleus consists of a single positively charged proton and no neutrons; it has one electron in neutral atoms. The mass of protium is about 1.007825 u and it has nuclear spin 1/2. It is stable and non-radioactive.

Natural abundance: In the universe, almost all hydrogen is protium. On Earth, natural hydrogen consists of about 99.98% protium, with deuterium and tritium present only in trace amounts.

Chemistry and bonding: Protium forms the diatomic molecule H2, the simplest and most abundant molecule in the universe. Its chemical behavior mirrors that of other hydrogen isotopes, with small kinetic isotope effects that can influence reaction rates and equilibrium in some cases.

Nuclear and spectral properties: Protium is stable, with ionization energy 13.598 eV. The 1H nucleus has spin 1/2, which underpins proton NMR and contributes to various spectral features used in chemistry and astronomy.

Applications and significance: Protium features prominently in fusion research, isotopic labeling, and as the primary reference form of hydrogen in chemistry and physics. Its ubiquity and simplicity make it a central reference in both laboratory studies and observational astrophysics.