Hydrogen (H)

Hydrogen is the lightest and most abundant chemical element in the universe, with atomic number 1, consisting of one proton and one electron in its neutral atomic form, and existing primarily as the diatomic molecule H2 under standard conditions. It is a colorless, odorless, highly flammable gas with the lowest density of any gas, low boiling point (-252.87°C), and high thermal conductivity due to weak intermolecular forces and rapid molecular diffusion. Chemically, hydrogen exhibits unique properties, forming strong covalent bonds in compounds like water (H2O) and hydrocarbons, acting as both a reducing agent and, in hydrides, an oxidizing agent; its H-H bond dissociation energy is 435.7 kJ/mol, making H2 relatively unreactive without catalysts. Hydrogen plays essential roles in biological molecules through C-H, O-H, and N-H bonds and hydrogen bonding that stabilizes structures like proteins and DNA. While ubiquitous in organic chemistry and energy applications like fuel cells, hydrogen is not a therapeutic target such as a receptor, enzyme, or transporter; it lacks specific drug-binding sites or disease-modifying roles amenable to pharmacological modulation. Safety challenges include its explosiveness in air (4-74% concentrations) and invisibility of flames, but these relate to industrial handling rather than therapeutic contexts.

Other names

Dihydrogenmolecular hydrogenH2