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 of B (Boron) Enhanced Bohr Model of B (Boron) Bohr Model: B (Boron) Orbital Diagram of B (Boron)

Properties

Atomic Radius
85 pm
Molar 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
Energy
Proton Affinity
Electron Affinity
0.279723 eV/particle
Ionization Energy
8.298019 eV/particle
Heat of Vaporization
504.5 kJ/mol
Heat of Fusion
23.6 kJ/mol
Heat of Formation
565 kJ/mol
Electrons
Electron Shells2, 3
Valence Electrons3
Electron Configuration[He] 2s2 2p1
Oxidation States-5, -1, 0, 1, 2, 3
Electronegativity
2.04
Electrophilicity
1.1470276511768214 eV/particle
Phases
PhaseSolid
Gas Phase
Boiling Point
4,273.15 K
Melting Point
2,350.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color
Black
Appearanceblack-brown
Refractive Index
Thermodynamic Properties
Thermal Conductivity
27.4 W/(m K)
Thermal Expansion
0.000006 1/K
Molar Heat Capacity
11.087 J/(mol K)
Specific Heat Capacity
1.026 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
TypeInsulator
Electrical Conductivity
0.0000000001 MS/m
Electrical Resistivity
10,000 m Ω
Superconducting Point
Magnetism
Typediamagnetic
Magnetic Susceptibility (Mass)
-0.0000000087 m³/Kg
Magnetic Susceptibility (Molar)
-0.0000000000941 m³/mol
Magnetic Susceptibility (Volume)
-0.0000214
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal StructureSimple Trigonal (TET)
Lattice Constant
8.73 Å
Lattice Angles1.01334, 1.01334, 1.01334
Mechanical Properties
Hardness
9.3 MPa
Bulk Modulus
320 GPa
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound
16,200 m/s
Classification
CategoryMetalloids, Metalloids
CAS GroupIIIB
IUPAC GroupIIIA
Glawe Number86
Mendeleev Number81
Pettifor Number86
Geochemical Class
Goldschmidt Classlitophile
Other
Gas Basicity
Dipole Polarizability
20.5 ± 0.1 a₀
C6 Dispersion Coefficient
99.5 a₀
AllotropesAlpha Rhombohedral Boron, Beta Rhombohedral Boron, Alpha Tetragonal Boron
Neutron Cross Section
760
Neutron Mass Absorption
2.4
Quantum Numbers2P1/2
Space Group166 (R_3m)

Isotopes of Boron

Stable Isotopes2
Unstable Isotopes14
Radioactive Isotopes13

6B

AbundanceRadioactive ☢️
Relative Atomic Mass
6.0508 ± 0.00215 Da
Mass Number6
G-Factor
Half Life
Spin2
Quadrupole Moment
Discovery Year
Parity-

6B Decay Modes
Decay ModeIntensity
2p (2-proton emission)%

7B

AbundanceRadioactive ☢️
Relative Atomic Mass
7.029712 ± 0.000027 Da
Mass Number7
G-Factor
Half Life
570 ± 14 ys
Spin3/2
Quadrupole Moment
Discovery Year1967
Parity-

7B Decay Modes
Decay ModeIntensity
p (proton emission)100%

8B

AbundanceRadioactive ☢️
Relative Atomic Mass
8.024607315 ± 0.000001073 Da
Mass Number8
G-Factor
0.51775 ± 0.00015
Half Life
771.9 ± 0.9 ms
Spin2
Quadrupole Moment
0.0643 ± 0.0014
Discovery Year1950
Parity+

8B Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
β+α (β+-delayed α emission)100%

9B

AbundanceRadioactive ☢️
Relative Atomic Mass
9.013329645 ± 0.000000969 Da
Mass Number9
G-Factor
Half Life
800 ± 300 zs
Spin3/2
Quadrupole Moment
Discovery Year1940
Parity-

9B Decay Modes
Decay ModeIntensity
p (proton emission)100%

10B

Abundance
19.65 ± 0.44
Relative Atomic Mass
10.012936862 ± 0.000000016 Da
Mass Number10
G-Factor
0.60015453333333 ± 0.00000026666666666667
Half Life
Spin3
Quadrupole Moment
0.0846 ± 0.0002
Discovery Year1920
Parity+

11B

Abundance
80.35 ± 0.44
Relative Atomic Mass
11.009305166 ± 0.000000013 Da
Mass Number11
G-Factor
1.792252 ± 0.00000066666666666667
Half Life
Spin3/2
Quadrupole Moment
0.04059 ± 0.0001
Discovery Year1920
Parity-

12B

AbundanceRadioactive ☢️
Relative Atomic Mass
12.014352638 ± 0.000001418 Da
Mass Number12
G-Factor
1.003 ± 0.001
Half Life
20.2 ± 0.02 ms
Spin1
Quadrupole Moment
0.0132 ± 0.0003
Discovery Year1935
Parity+

12B Decay Modes
Decay ModeIntensity
β (β decay)100%
βα (β-delayed α emission)0.6%

13B

AbundanceRadioactive ☢️
Relative Atomic Mass
13.017779981 ± 0.000001073 Da
Mass Number13
G-Factor
2.1185333333333 ± 0.00033333333333333
Half Life
17.16 ± 0.18 ms
Spin3/2
Quadrupole Moment
0.0365 ± 0.0008
Discovery Year1956
Parity-

13B Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)0.266%

14B

AbundanceRadioactive ☢️
Relative Atomic Mass
14.02540401 ± 0.000022773 Da
Mass Number14
G-Factor
0.5925 ± 0.0025
Half Life
12.36 ± 0.29 ms
Spin2
Quadrupole Moment
0.0297 ± 0.0008
Discovery Year1966
Parity-

14B Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)6.04%
2n (2-neutron emission)%

15B

AbundanceRadioactive ☢️
Relative Atomic Mass
15.031087023 ± 0.000022575 Da
Mass Number15
G-Factor
1.7726666666667 ± 0.01
Half Life
10.18 ± 0.35 ms
Spin3/2
Quadrupole Moment
0.0379 ± 0.0011
Discovery Year1966
Parity-

15B Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)98.7%
2n (2-neutron emission)1.5%

16B

AbundanceRadioactive ☢️
Relative Atomic Mass
16.039841045 ± 0.000026373 Da
Mass Number16
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year2000
Parity-

16B Decay Modes
Decay ModeIntensity
n (neutron emission)%

17B

AbundanceRadioactive ☢️
Relative Atomic Mass
17.046931399 ± 0.000219114 Da
Mass Number17
G-Factor
1.7 ± 0.013333333333333
Half Life
5.08 ± 0.05 ms
Spin3/2
Quadrupole Moment
0.0385 ± 0.0015
Discovery Year1973
Parity-

17B Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)63%
2n (2-neutron emission)12%
3n (3-neutron emission)3.5%
4n0.4%

18B

Abundance
Relative Atomic Mass
18.055601683 ± 0.00021918 Da
Mass Number18
G-Factor
Half Life
Spin2
Quadrupole Moment
Discovery Year2010
Parity-

18B Decay Modes
Decay ModeIntensity
n (neutron emission)100%

19B

AbundanceRadioactive ☢️
Relative Atomic Mass
19.064166 ± 0.000564 Da
Mass Number19
G-Factor
Half Life
2.92 ± 0.13 ms
Spin3/2
Quadrupole Moment
Discovery Year1984
Parity-

19B Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)71%
2n (2-neutron emission)17%
3n (3-neutron emission)9.1%

20B

AbundanceRadioactive ☢️
Relative Atomic Mass
20.074505644 ± 0.000586538 Da
Mass Number20
G-Factor
Half Life
Spin1
Quadrupole Moment
Discovery Year2018
Parity-

20B Decay Modes
Decay ModeIntensity
n (neutron emission)100%
β n (β-delayed neutron emission)%
2n (2-neutron emission)%

21B

AbundanceRadioactive ☢️
Relative Atomic Mass
21.084147485 ± 0.00059975 Da
Mass Number21
G-Factor
Half Life
Spin3/2
Quadrupole Moment
Discovery Year2018
Parity-

21B Decay Modes
Decay ModeIntensity
2n (2-neutron emission)100%

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
Etymology (Name Origin)From Arabic and Persian words for borax.
PronunciationBO-ron (English)
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).

Abundance
Abundance in Earth's crust
Abundance in Oceans
4.44 mg/L
Abundance in Human Body
0.00007 %
Abundance in Meteor
0.00016 %
Abundance in Sun
0.0000002 %
Abundance in Universe
0.0000001 %

Nuclear Screening Constants

1s0.3205
2p2.5786
2s2.4238