B
Boron
Element 5 · Metalloid
Boron (B)
Boron is a hard, black metalloid that is rare in the universe but concentrated in Earth’s crust in borate minerals.
- Metalloid
- Period 2
- Group 13
- p-block
- solid at room temperature
Key properties
- Atomic mass
- 10.81
- u
- Electron configuration
- [He] 2s2 2p1
- Melting point
- 2,074.9 °C
- 2,348 K
- Boiling point
- 3,999.9 °C
- 4,273 K
- Density
- 2.37 g/cm³
- Electronegativity
- 2.04
- Pauling
- Atomic radius
- 192 pm
- van der Waals
- 1st ionisation energy
- 8.298 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about boron
- 01
Boron is made almost entirely by cosmic rays splitting heavier nuclei, not by stars.
- 02
Boron carbide is one of the hardest known materials and is used in tank armour and body armour.
- 03
Plants need boron to build cell walls; a shortage causes hollow stems and cracked fruit.
Applications
What is boron used for?
- Borosilicate (Pyrex) glass
- Fibreglass insulation
- Neutron-absorbing control rods
- Detergents and bleach
History
Discovery & name origin
Discovered by
Joseph Louis Gay-Lussac, Louis Jacques Thénard, Humphry Davy
Year
Where
France and England
Name origin
From borax, which comes from Arabic buraq and Persian burah.
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 5
- Atomic mass
- 10.81 u
- Group
- 13
- Period
- 2
- Block
- p-block
- Electron configuration
- [He] 2s2 2p1
- Full configuration
- 1s2 2s2 2p1
- Electrons per shell
- 2, 3
- Electronegativity (Pauling)
- 2.04
- Electron affinity
- 0.277 eV
- Atomic radius (van der Waals)
- 192 pm
- Stable isotopes
- 2
Oxidation states
Highlighted: common oxidation states (+3).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st800.6
- 2nd2,427.1
- 3rd3,659.7
- 4th25,025.8
- 5th32,826.7
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 2,348 K · 2,074.9 °C · 3,766.7 °F
- Boiling point
- 4,273 K · 3,999.9 °C · 7,231.7 °F
- Density
- 2.37 g/cm³
- Molar heat capacity
- 11.087 J/(mol·K)
- Appearance
- Black-brown
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Boron questions
What is B on the periodic table?
B is the symbol for boron, element 5 on the periodic table. It sits in group 13, period 2, in the metalloid category, and has an atomic mass of 10.81.
What is the atomic number of boron?
Boron has atomic number 5, so every boron atom has 5 protons in its nucleus. Its symbol is B and its atomic mass is 10.81.
Who discovered boron?
Boron was discovered by Joseph Louis Gay-Lussac, Louis Jacques Thénard and Humphry Davy in 1808 (France and England). The name comes from from borax, which comes from Arabic buraq and Persian burah.
What is boron used for?
Boron is used for: borosilicate (Pyrex) glass; fibreglass insulation; neutron-absorbing control rods; detergents and bleach.
Is boron a metal?
No. Boron is classed as a metalloid, with properties between metals and nonmetals.
What is the electron configuration of boron?
The electron configuration of boron is [He] 2s2 2p1. Its 5 electrons are arranged in shells as 2, 3.