001Reactive nonmetal · Group 1 · Period 1
Hydrogen
Hydrogen (H) is element 1, a reactive nonmetal in the s-block — group 1, period 1. It is a gas at room temperature with 1 electron shells (1) and an atomic mass of 1.008 u.
- Atomic mass
- 1.008 u
- Phase · STP
- gas
- Melting
- 14 K · -259 °C
- Boiling
- 20 K · -253 °C
- Electronegativity
- 2.2
- Density
- 0.08988 g/cm³
Photograph — User:Jurii, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, source: https://images-of-elements.com/hydrogen.php
Emission spectrum
The visible light Hydrogen emits when energised — its unique spectral fingerprint.
Identity
- Atomic number
- 1
- Standard atomic weight
- 1.008 u
- Category
- Reactive nonmetal
- Group
- 1
- Period
- 1
- Block
- s-block
- Oxidation states
- +1, -1
Physical properties
- Melting point
- 14 K · -259 °C
- Boiling point
- 20 K · -253 °C
- Density
- 0.08988 g/cm³
- Molar heat capacity
- 28.836 J/(mol·K)
- Atomic radius
- 120 pm
- Electron affinity
- 72.769 kJ/mol
Atomic structure
1protons
0neutrons
1electrons
1valence e⁻
- Noble-gas notation
- 1s1
- Full configuration
- 1s1
- Electrons per shell
- 1
Periodic trends
Where Hydrogen ranks across all 118 elements.
Discovery
- Discovered
- 1766
- Discovered by
- Henry Cavendish
- Named by
- Antoine Lavoisier
- Appearance
- colorless gas