Elements
Hydrogen ( H )
- Atomic number: 1
- Appearance: colorless gas
- Standard atomic weight: 1.008
- Group: hydrogen
- Period: 1
- Electron configuration: 1s1
- Element category: reactive nonmetal
- Melting point: 13.99 K
- Boiling point: 20.271 K
- Sublimation point: Standard Temperature ( 273.15 ) and Pressure ( 1 bar = 105 Pa )
- Phase at STP: ( H2 ) gas
- Density at STP:
- Heat of fusion: ( H2 ) 0.117 kJ/mol
- Heat of vaporization: ( H2 ) 0.904 kJ/mol
- Molar heat capacity: ( H2 ) 28.836 kJ/(mol·K)
- Oxidation states: +1, -1
- Electronegativity: Pauling scale: 2.2
- Covalent radius: 31 pm (1×10−12 m)
- Van der Waals radius: 120 pm (1×10−12 m)
- Crystal structure: hexagonal
- Speed of sound: 1310 m/s (gas, 27 °C)
- Thermal expansion:
- Thermal conductivity: 0.1805 W/(m·K)