Boron Facts

Boron is the fifth element of the periodic table. These boron facts contain chemical and physical data along with general information and history.

Element cell for Boron
Boron periodic table cell.

Basic Boron Facts

Name: Boron

Atomic Number: 5

Element Symbol: B

Group: 13

Period: 2

Block: p

Element Family: metalloid

Atomic Mass: [10.806; 10.821] IUPAC guidelines. For single value, use 10.811.

Electron Configuration: [He]2s22p(shorthand) or 1s22s22p(full)

Discovery: Three different scientists isolated boron in 1808.
Borax has been known and used for centuries. It was used in ceramic glazes and in metallurgy but no one isolated any element from borax. In 1808, Sir Humphry Davy used electrolysis on borax solutions and noticed a brown mass forming at one electrode. He later used potassium to reduce boron from boric acid. Across the channel in France, Joseph Louis Gay-Lussac and Louis Jacques Thénard isolated boron by reducing boric acid with iron at high temperatures. It wasn’t until 1824 boron was identified as an element by Swedish chemist Jöns Jakob Berzelius.

Name Origin: The name boron comes from mineral it was extracted from: borax. That name comes from the Arabic word buraq, the common name for the stone.

Natural Isotopes:

Natural boron is comprised of two stable isotopes: B-10 and B-11. Eleven other isotopes have been produced in laboratory conditions ranging from B-7 to B-17.

Boron-10 is a stable isotope containing 5 neutrons. 19.78% of natural boron is boron-10.

Boron-11 is a stable isotope containing 6 neutrons. 80.22% of natural boron is boron-11.

Small sample of boron.(Jurii)

Physical Data

Density: 2.34 g/cm3

Melting Point: 2350 K (2077 ºC or 3771 ºF)

Boiling Point: 4000 K (4273 ºC or 7232 ºF)

State at 20ºC: Solid

Heat of Fusion: 50.2 kJ/mol

Heat of Vaporization: 508 kJ/mol

Molar Heat Capacity: 11.087 J/mol·K

Boron Atom
Electron configuration of a boron atom.

Atomic Data

Atomic Radius: 0.90 Å (empirical)

Covalent Radius: 0.84 Å

Van der Waals Radius:  1.92 Å

Electron Affinity: 26.989 kJ/mol

Electronegativity: (Pauling scale): 2.04

1st Ionization Energy: 800.637 kJ/mol

2nd Ionization Energy: 2427.069 kJ/mol

3rd Ionization Energy: 3659.751 kJ/mol

4th Ionization Energy: 25025.905 kJ/mol

5th Ionization Energy: 32826.802 kJ/mol

Common Oxidation States: +3 (common), +2, +1, -5 (uncommon)

Green Fire
Green fire can be produced using borax or boric acid and methanol. Credit: Anne Helmenstine

Fun Boron Facts

  • Pure boron is a dark amorphous powder.
  • Boron has the highest melting point of the metalloids.
  • Boron has the highest boiling point of the metalloids.
  • The boron-10 isotope is used as a neutron absorber in nuclear reactors and is part of the emergency shutdown systems.
  • Boron is used in semiconductor production as dopant to make p-type semiconductors.
  • Boron burns bright green in flame tests.
  • Boron’s green flame properties are used in fireworks.
  • Boron is added to glass to increase its resistance to heat shock. Most laboratory glassware is made from borosilicate glass.
  • Boron is a major component of the super strong neodymium magnets. Nd2Fe14B is the chemical formula for these magnets.
  • Boron is an essential nutrition element for plants. It is mildly toxic to humans and deadly to arthropods. Boric acid is often used for pest control.
  • The United States and Turkey have the largest deposits of borax.

Learn more about elements on the periodic table.