Hydrogen is a chemical element with chemical symbol H and atomic number 1. Hydrogen is the lightest element and its monatomic form (H) is the most abundant chemical substance, constituting roughly 75% of the Universe's baryonic mass. Non-remnant stars are mainly composed of hydrogen in its plasma state.Symbol: H
Atomic number: 1
Electron configuration: 1s1
Van der Waals radius: 120 pm
Atomic mass: 1.00794 ± 0.00001 u
Discoverer: Henry Cavendish