Hydrogen. Molecular model of hydrogen gas. The two white spheres represent individual hydrogen atoms and the grey bar represents the single bond between them. Two forms of hydrogen exist:- orthohydogen (75%) and parahydrogen (25%). The former's two nuclei spin in parallel, the latter's spin antiparallel. They have slightly different boiling and melting points. Hydrogen is the lightest element, and is a widespread constituent of water, minerals, and organic matter. It is produced by electrolysis of water or reactions between acids and metals. Hydrogen is used industrially in hydrogenation of fats and oils, and in hydrocarbon synthesis.