Boron
A hard metalloid essential to heat-resistant glass.
Inside the Boron atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Boron atom step by step.
Electron configuration
[He] 2s2 2p1
A neutral Boron atom has 5 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Solid
- Melting point
- 2349 K (2076 °C)
- Boiling point
- 4200 K (3927 °C)
- Density
- 2.34 g/cm³
- Electronegativity
- 2.04 Pauling
- Atomic radius
- 85 pm
- 1st ionization energy
- 801 kJ/mol
- Category
- Metalloids
Discovery & naming
- Discovered
- 1808
- Discovered by
- Humphry Davy, Gay-Lussac, and Thénard
- Origin of name
- From borax, via Arabic 'buraq'.
Notable uses
Heat-resistant borosilicate glass, detergents, and semiconductors.
Where Boron comes from
Cosmic ray spallation
Like beryllium, chiefly a fragment: cosmic rays striking carbon and oxygen nuclei chip it loose.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 5
- Atomic mass
- 10.81
- Category
- Metalloids
- Group · Period
- 13 · 2
- Block
- p-block
- Shells
- 2 · 3