Boron

5
B
Group
13
Period
2
Block
p
Protons
Electrons
Neutrons
5
5
6
General Properties
Atomic Number
5
Atomic Weight
10.811
Mass Number
11
Category
Metalloids
Color
Black
Radioactive
No
From the Arabic word Buraq, Persian Burah
Crystal Structure
Simple Trigonal
History
Boron compounds have been known for thousands of years, but the element was not discovered until 1808 by Sir Humphry Davy and by Gay-Lussac and Thenard.

Boron was not recognized as an element until it was isolated in 1808 by Sir Humphry Davy and by Joseph Louis Gay-Lussac and Louis Jacques Thénard.

Jöns Jakob Berzelius identified boron as an element in 1824.
Electrons per shell
2, 3
Electron Configuration
[He] 2s2 2p1
B
Boron is an essential nutrient for all green plants
Physical Properties
Phase
Solid
Density
2.34 g/cm3
Melting Point
2349.15 K | 2076 °C | 3768.8 °F
Boiling Point
4200.15 K | 3927 °C | 7100.6 °F
Heat of Fusion
50 kJ/mol
Heat of Vaporization
507 kJ/mol
Specific Heat Capacity
1.026 J/g·K
Abundance in Earth's crust
0.00086%
Abundance in Universe
1×10-7%
Pure
Image Credits: Images-of-elements
Pure crystalline boron, front side
CAS Number
7440-42-8
PubChem CID Number
5462311
Atomic Properties
Atomic Radius
90 pm
Covalent Radius
84 pm
Electronegativity
2.04 (Pauling scale)
Ionization Potential
8.298 eV
Atomic Volume
4.6 cm3/mol
Thermal Conductivity
0.274 W/cm·K
Oxidation States
1, 2, 3
Applications
Boron oxide is used in glassmaking and ceramics.

Borax is used in making fiberglass, as a cleansing fluid, a water softener, insecticide, herbicide and disinfectant.

Boric acid is used as a mild antiseptic and as a flame retardant.

Boron shielding is used as a control for nuclear reactors.
Elemental boron, boron oxide, boric acid, borates and many organoboron compounds are non-toxic
Isotopes
Stable Isotopes
10B, 11B
Unstable Isotopes
7B, 8B, 9B, 12B, 13B, 14B, 15B, 16B, 17B, 18B, 19B