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Boron (B)

Boron is a chemical element of the periodic table with chemical symbol B and atomic number 5 with an atomic weight of 10.806 u and is classed as metalloid and is part of group 13 (boron group). Boron is solid at room temperature.

Boron in the periodic table

Atomic number5
Group13 (Boron group)
Color Black
Number of protons5 p+
Number of neutrons6 n0
Number of electrons5 e-
From Wikipedia, the free encyclopediaBoron 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.

Physical properties

Phase at STPSolid
Density2.08 g/cm3
Atomic weight10.806 u

Thermal properties

Melting point2349 K
2075.85 °C
3768.53 °F
Boiling point4200 K
3926.85 °C
7100.33 °F
Heat of vaporization507.8 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)2.04
Electron affinity26.989 kJ/mol
Oxidation states−5, −1, 0, +1, +2, +3
(a mildly acidic oxide)
Ionization energies
  1. 800.6 kJ/mol
  2. 2427.1 kJ/mol
  3. 3659.7 kJ/mol
  4. 25025.8 kJ/mol
  5. 32826.7 kJ/mol

Electron configuration for boron

Electron configuration
Shorthand configuration
[He] 2s2 2p1
Electron configuration
Full configuration
1s2 2s2 2p1
Electron configuration chart
Electrons per shell2, 3
Valence electrons 3
Valency electrons 3
Bohr model
BoronElectron shell for Boron, created by Injosoft ABB
Figure: Shell diagram of Boron (B) atom.
Orbital Diagram

The history of Boron

DiscoveryJoseph Louis Gay-Lussac, Louis Jacques Thénard (1808)
First isolationHumphry Davy (1808)
Discovery of boron
Boron was not recognized as an element until it was isolated by Sir Humphry Davy and by Joseph Louis Gay-Lussac and Louis Jacques Thénard. In 1808 Davy observed that electric current sent through a solution of borates produced a brown precipitate on one of the electrodes. In his subsequent experiments, he used potassium to reduce boric acid instead of electrolysis. He produced enough boron to confirm a new element and named it boracium. Gay-Lussac and Thénard used iron to reduce boric acid at high temperatures. By oxidizing boron with air, they showed that boric acid is its oxidation product. Jöns Jacob Berzelius identified it as an element in 1824.


List of unique identifiers for Boron in various chemical registry databases
CAS Number7440-42-8
ChemSpider ID4575371
EC number231-151-2
PubChem CID Number5462311