Boron

Boron (B)

An element of group 13 of the periodic table. There are two allotropes, amorphous boron is a brown power, but metallic boron is black. The metallic form is hard (9.3 on Mohs' scale) and a bad conductor in room temperatures. It is never found free in nature. Boron-10 is used in nuclear reactor control rods and shields. It was discovered in 1808 by Sir Humphry Davy and by J.L. Gay-Lussac and L.J. Thenard.
Atomic Number5
Atomic Weight10.81
Mass Number11
Group13
Period2
Blockp
Protons5 p+
Neutrons6 n0
Electrons5 e-
Boron.jpg Electron shell 005 Boron.png Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram

Properties

Atomic Radius
85 pm
Atomic Volume
Covalent Radius
85 pm
Metallic Radius
80 pm
Ionic Radius
1 pm
Crystal Radius
15 pm
Van der Waals radius
192 pm
Density
2.34 g/cm³
Boiling Point
3,931 K
Melting Point
2,573 K
Electrons per shell2, 3
Electronegativity
2.04
Electrophilicity
1.1470276511768 eV/particle
Proton Affinity
Electron Affinity
0.279723 eV/particle
Ionization Potential
8.298019 eV/particle
Heat of Vaporization
504.5 kJ/mol
Heat of Fusion
23.6 kJ/mol
Heat of Formation
565 kJ/mol
Molar Heat Capacity
11.087 J/(mol K)
Specific Heat Capacity
1.026 J/(g⋅K)
Thermal Conductivity
27.4 W/(m K)
Gas Basicity
Dipole Polarizability
20.5 a₀
C6 Dispersion Coefficient
99.5 a₀
Oxidation States1, 2, 3
Color
Black
Crystal StructureSimple Trigonal (TET)
Lattice Constant
8.73 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration[He] 2s2 2p1
Magnetic Ordering
Magnetic Susceptibility
PhaseSolid
Poisson Ratio
Shear Modulus
Young's Modulus
Allotropes
Alternate Names
Adiabatic Index
Appearance
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Electrical
Hardness
Magnetic Susceptibility
Magnetic
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
Classification
CategoryMetalloids, Metalloids
CAS GroupIIIB
IUPAC GroupIIIA
Glawe Number86
Mendeleev Number81
Pettifor Number86
Geochemical Class
Goldschmidt Classlitophile
Radioactivity
RadioactiveNo
Decay Mode
Half-Life
Lifetime
Abundance
Abundance in Earth's crust
Abundance in Oceans
4.44 mg/L
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universe1×10-7%

Isotopes of Boron

Stable Isotopes
10B 11B
Unstable Isotopes
6B 7B 8B 9B 12B 13B 14B 15B 16B 17B 18B 19B

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. From the Arabic word Buraq, Persian Burah

DiscoverersSir H. Davy, J.L. Gay-Lussac, L.J. Thénard
Discovery LocationEngland/France
Discovery Year1808
Name OriginFrom Arabic and Persian words for borax.
Elemental boron, boron oxide, boric acid, borates and many organoboron compounds are non-toxic
Boron is an essential nutrient for all green plants

Uses

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. Used with titanium & tungsten to make heat resistant alloys for jets & rockets.

Sources

Obtained from kernite, a kind of borax (Na2B4O7.10H2O). High purity boron is produced by electrolysis of molten potassium fluroborate and potassium chloride (KCl).