1
H
Hydrogen
1.008
Hydrogen (H)
NonmetalGroup 1Period 1s-block-block
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.
Latin name: Hydrogenium
Atomic Number
1
Atomic Mass
1.008 g/mol
Phase (STP)
Gas
Electron Config.
1s¹
General
SymbolH
Atomic Number1
Atomic Mass1.008 g/mol
CategoryNonmetal
Group1
Period1
Blocks-block
Electron Configuration1s¹
Valence Electrons1
ColourColorless
Appearancecolorless gas
CAS NumberCAS1333-74-0
Physical Properties
Phase (STP)Gas
Density0.00009 g/cm³
Melting Point-259.14°C · -434.45°F · 14.01 K
Boiling Point-252.87°C · -423.17°F · 20.28 K
Atomic Properties
Atomic Radius53 pm
Covalent Radius31 pm
Van der Waals Radius120 pm
Electronegativity2.2 Pauling
Ionization Energy1312 kJ/mol
Electron Affinity72.8 kJ/mol
Oxidation States-1, +1
Ion ChargeH⁺
Thermodynamic
Molar Heat28.836 J/(mol·K)
Electromagnetic
Electrical TypeInsulator
Abundance
In Universe75.0000%
In Sun75.0000%
In Earth's Crust0.1400%
In Oceans11.0000%
In Humans10.0000%
In Meteorites2.4000%
Discovery & History
Discovery Year1766
Discovered ByHenry Cavendish
Country of DiscoveryEngland
Named ByAntoine Lavoisier
Isotopes of Hydrogen
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| H-1 | 99.9885% | Stable | — |
| H-2 | 0.0115% | Stable | — |
| H-3 | — | 12.32 years | β⁻ |