Boron
Boron is a metalloid chemical element with symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in both the Solar system and the Earth's crust. Boron is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals.
A stylized shell model. Electrons are quantum objects, not particles following these literal paths. Sizes and motion are illustrative.
At a glance
- Atomic number
- 5
- Atomic mass
- 10.81 u
- Phase
- Solid
- Density
- 2.08 g/cm³
- Melting point
- 2,349 K
- Boiling point
- 4,200 K
- First ionization energy
- 800.6 kJ/mol
- Electronegativity
- 2.04
- Electron affinity
- 26.989 kJ/mol
- Molar heat capacity
- 11.087 J/(mol·K)
- Period
- 2
- Appearance
- black-brown
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.