1H1.008

Hydrogen

Diatomic Nonmetal

Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.

Phase: GasAppearance: colorless gas

Physical Properties

Atomic Mass1.008 u

Density0.08988 g/cm³

Melting Point13.99 K

Boiling Point20.271 K

Molar Heat28.836 J/(mol·K)

Period1

PhaseGas

Chemical Properties

Electron Configuration1s1

Semantic Config1s1

Shells1

Electron Affinity72.769 kJ/mol

Electronegativity2.2

Ionization Energies

IE1: 1312 kJ/mol

Discovery

Discovered byHenry Cavendish

Named byAntoine Lavoisier

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