Hydrogen - The lightest element

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Atomic Structure

Hydrogen is the simplest element, consisting of a single proton and one electron, with no neutrons in its most common form (protium). It has an atomic number of 1 and is the most abundant element in the Universe.

Abundance and Role in Nature

Hydrogen makes up roughly 75% of the universe’s elemental mass. It is present in stars (fueling their fusion), in water (H₂O), and in organic molecules. On Earth, it mostly exists bound to other elements, rarely as free H₂ gas because it easily escapes Earth’s gravity.

Industrial and Energy Uses

Hydrogen is central to ammonia synthesis, petroleum refining, and hydrogenation processes, and is increasingly being produced as low-emission “green hydrogen” through water electrolysis—an approach promoted under the Hydrogen Shot initiative of the U.S. Department of Energy.

Isotopes of Hydrogen

Atoms contain Protons and Neutrons in the nucleus, with Electrons orbiting around. Changing neutron number creates different Isotopes of the same element.

${}_1{}^{1}H\text{(Protium: 1 p, 0 n)}$

${}_1{}^{2}H\text{(Deuterium: 1 p, 1 n)}$

${}_1{}^{3}H\text{(Tritium: 1 p, 2 n)}$

They are chemically similar but differ greatly in mass and nuclear stability, which strongly affects their behavior in Nuclear fusion.

Deuterium

Deuterium (²H or D) is stable and makes up about 0.015% of natural hydrogen, mostly in seawater as heavy water (D₂O). The extra neutron doubles its mass, giving it higher density and slightly slower molecular reaction rates while keeping chemistry nearly unchanged.

Deuterons can fuse through two main branches:

${}_1{}^{2}H+{}_1{}^{2}H\to {}_1{}^{3}H+{}_1{}^{1}H+4.0\text{MeV}$

${}_1{}^{2}H+{}_1{}^{2}H\to {}_2{}^3\mathrm{He}+{}_0{}^{1}n+3.3\text{MeV}$

Deuterium is extracted from water by electrolysis or cryogenic distillation and also serves as a neutron moderator in Nuclear fission reactors.

Tritium

Tritium (³H or T) is radioactive with a half-life of 12.3 years. It contains one proton and two neutrons, emits low-energy beta particles, and occurs only in trace amounts naturally from cosmic-ray reactions in the Atmosphere. In reactors, it is bred from Lithium:

${}_3{}^6\mathrm{Li}+{}_0{}^{1}n\to {}_2{}^4\mathrm{He}+{}_1{}^{3}H+4.8\text{MeV}$

Tritium is crucial in fusion because it fuses efficiently with deuterium:

${}_1{}^{2}H+{}_1{}^{3}H\to {}_2{}^4\mathrm{He}+{}_0{}^{1}n+17.6\text{MeV}$

It diffuses readily through metals and biological systems, so fusion facilities use sealed fuel loops, continuous monitoring, and strict containment.