ELEMENTLE

Element 5 · Metalloid

Boron

Period 2 · Group 13

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.

Three reasons Boron stands out

  1. 1

    Used in heat-resistant glass.

  2. 2

    Used in nuclear reactor control rods because it absorbs neutrons so effectively.

  3. 3

    It is an essential nutrient for plant growth and reproduction.

Boron’s talent for extremes

Boron sits between metallic and nonmetallic behavior. Its strong covalent networks help borosilicate glass survive sudden temperature changes, while boron carbide ranks among the hardest known materials. The isotope boron-10 captures neutrons so readily that it is used to help control nuclear reactions.

Boron at a glance
Atomic number / protons5
SymbolB
Family (Elementle)Metalloid
Classification (PubChem)Metalloid
Period2
Group13
Atomic mass (u)10.81
Standard stateSolid
Electron configuration[He]2s2 2p1
Reported oxidation states+3
Electronegativity (Pauling)2.04
Atomic radius (pm)192
First ionization energy (eV)8.298
Electron affinity (eV)0.277
Density (g/cm³)2.37
Melting point2348 K (2,074.85 °C)
Boiling point4273 K (3,999.85 °C)
Discovery (PubChem)1808

Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.

Sources & further reading

PubChem: Boron · Boron on Wikipedia

The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.