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About Boron

Boron Bohr

Boron is the only non-metallic element of the periodic table family that includes aluminum, gallium, and indium. Classified as a metalloid, or semimetal, the element can mimic the typical behavior of either a metal or a nonmetal, depending on the type of reaction involved. The only nonmetal with 3 electrons in its outer shell to contribute to bonds, boron is a strong electron-pair acceptor (a strong Lewis acid) with a very high affinity for oxygen and is one of the few elements along carbon and nitrogen known to form stable compounds with triple bonds. Like its neighbor carbon, elemental boron has multiple allotropes, or structural forms, all of which are extremely hard: crystalline boron is a brittle, lustrous sold ranging in appearance from jet black to silvery gray that is a poor electrical conductor; another crystalline form is red in appearance; and amorphous boron is a dark brown powder lower in density than the crystalline forms. Boron is also similar to carbon in that both are able to form covalently bonded networks of molecules, and the two are the only elements that form multiple hydride compounds.

The name boron comes from the Persian or Arabic terms for the mineral borax (burah or buraq, respectively). Borax and boric acid have been known since ancient times in Europe, Tibet, and China, being used by craftsmen to reduce melting point of other materials used in glassmaking and other applications. The first written reference to boron-containing compounds was by the 9th century Persian alchemist Rhazes who classified one of six groups of minerals as “boraces.” The element was first isolated in 1808 independently by English chemist Sir Humphry Davy and French chemists Joseph-Louis Gay-Lussac and Louis-Jacque Thenard. Later, Henry Moisson isolated a more pure sample by reducing boron trioxide with magnesium, a method that still bears his name.

The chief commercial application for boron is the use of borax (sodium tetraborate pentahydrate, Na2B4O7• 10H2O) in soaps and household detergents, water-softening compounds to remove alkaline-earth ions like calcium and magnesium from water, adhesives, cosmetics, fire retardants, and glazes. It is also used to disinfect fruit and lumber, and additionally plays a role in the manufacturing of paper, leather, and plastics. Sodium borate is used to manufacture borosilicate glass, a high-strength glass that is resistant to heat, chemical attack, and thermal shock; applications for borosilicate glasses include bakeware, laboratory containers, and high quality optical glass, as well as serving as precursor materials for glass fiber insulation and textile glass fibers. Boron-containing glasses are generally preferred for flat display panel glass, as in LCDs, as such glasses have superior electrical and strength characteristics as compared to other glasses available for these applications.

Boron is also used in a number of alloy products, including neodymium iron boron magnets, which are the strongest magnets available and are found in microphones, magnetic switches, speakers, particle accelerators, and dozens of other electronic applications. Boron is also an important dopant molecule used in the production of semiconductor crystals. A number of boron compounds are also important in electronics, including the neutron-detecting scintillator material cadmium borate, and boron subphtalocyanines, organoboron dye molecules with optical properties that are of use in organic LEDs and photovoltaics. Some other organoboron compounds have medical uses, either as treatment agents, or as diagnostic markers.

Though not technically a metal, boron is playing an increasingly important role in advanced materials science due in part to the unique properties of hexagonal boron nitride, a semiconducting material capable of forming two-dimensional sheets similar to carbon-based graphene. Boron nitride and boron carbide are both superhard materials, and are used widely in cutting tools and as abrasives. Boron carbide is also a strong, heat-resistant material with a high strength-to-weight ratio, making it useful for armor and bulletproof vests. Additionally, boron carbide can absorb neutrons without forming dangerous long-lived radioactive waste, and it is therefore an important material in nuclear power plants. A number of other engineered advanced materials also contain boron. These include borane derivatives, of interest for a variety of specialized applications including hydrogen storage, and lithium borosilicide, a key component of lithium ion batteries.

Boron is relatively scarce element in the universe, produced only via cosmic ray spallation rather than in the cores of stars. Despite composing merely 0.0003% of the earth’s crust by mass, boron is very susceptible to fractionation in the earth’s crust and therefore tends to be concentrated in an deposits of an extensive array of borate (boron oxide)-containing minerals such as borax and kernite (its most common sources), colemanite, and ulexite. It is also present in meteorites, seawater, as a trace element in soils, and silicate minerals like tourmaline and datolite. Methods of obtaining boron include heating the oxide with powdered magnesium or aluminum, or passing an electric current through molten boron trichloride. The city of Boron in California, United States was named after the element and is home to the U.S. Borax Boron Mine, the world’s largest borax mine. The other major source of the element is deposits in Turkey, although the element also is known to accumulate in areas of thermal and volcanic activity.

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Compounds
Organometallics

Summary. Boron has an energy band gap of 1.50 to 1.56 eV, which is higher than that of either silicon or germanium. Optical characteristics include transmitting portions of the infrared. Boron is a poor conductor of electricity at room temperature but a good conductor at high temperature. Amorphous boron is used in pyrotechnic flares to provide a distinctive green color, and in rockets as an igniter. Boric acid is an important boron compound with major markets in textile products. Boron compounds High Purity (99.999%) Boron Oxide (B2O3) Powder High Purity (99.999%) Boron (B) Sputtering Target are used extensively in the manufacture of borosilicate glasses. The isotope Boron-10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons. Boron nitride has remarkable properties and can be used to make a material as hard as diamond. The nitride also behaves like an electrical insulator but conducts heat like a metal. Boron is available in forms with purities from 99% to 99.999% (ACS grade to ultra-high purity). Elemental forms include pellets, rod, wire and granules for evaporation source material purposes. Boron oxide isavailable in powder and dense pellet form for such uses as optical coating and thin film applications. Boron fluorides is an insoluble source of fluoride for uses in which oxygen is undesirable such as metallurgy, chemical and physical vapor deposition and in some optical coatings. Boron is also available in soluble forms including chlorides, and acetates. These compounds can be manufactured as solutions at specified stoichiometries.

Boron Properties

Boron (B) atomic and molecular weight, atomic number and elemental symbolBoron is a Block P, Group 13, Period 2 element. Boron Bohr ModelThe number of electrons in each of boron's shells is 2, 3 and its electron configuration is [He] 2s2 2p1. The boron atom has a radius of 90.pm and its Van der Waals radius is 192.pm. Elemental Boron In its elemental form, CAS 7440-42-8, boron has a black-brown appearance. Along with carbon and nitrogen, boron is one of the few elements in the periodic table known to form stable compounds featuring triple bonds. Boron is found in borates, borax, boric acid, colemanite, kernite, and ulexite. Boron was discovered by Joseph Louis Gay-Lussac and Louis Jacques Thénard in 1808. It was first isolated by Humphry Davy, also in 1808. The name Boron originates from a combination of carbon and the Arabic word buraqu meaning borax.

Symbol: B
Atomic Number: 5
Atomic Weight: 10.81
Element Category: metalloid
Group, Period, Block: 13, 2, p
Color: black
Other Names: Bore, Bor
Melting Point: 2077 °C, 3770.6 °F, 2350.15 K
Boiling Point: 4000 °C, 7232 °F, 4273.15 K
Density: 2.3 g/cm3 @ 20 °C
Liquid Density @ Melting Point: 2.08 g/cm3
Density @ 20°C: 2.34 g/cm3
Density of Solid: 2460 kg·m3
Specific Heat: 0.245 Cal/g/K @ 25 °C
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 22.2
Heat of Vaporization (kJ·mol-1): 504.5
Heat of Atomization (kJ·mol-1): 557.64
Thermal Conductivity: 0.274 W/cm/K @ 298.2 K
Thermal Expansion: 5–7 µm·m-1·K-1 @ 25 °C
Electrical Resistivity: 1.8 x 1012 µΩ·cm @ 0 °C
Tensile Strength: N/A
Molar Heat Capacity: 11.087 J·mol-1·K-1
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: N/A
Poisson Ratio: N/A
Mohs Hardness: ~9.5
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: (20 °C) 16,200 m·s-1
Pauling Electronegativity: 2.04
Sanderson Electronegativity: 2.28
Allred Rochow Electronegativity: 2.01
Mulliken-Jaffe Electronegativity: 2.04 (sp2 orbital)
Allen Electronegativity: 2.051
Pauling Electropositivity: 1.96
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 5
Protons: 5
Neutrons: 6
Electron Configuration: [He] 2s2 2p1
Atomic Radius: 90 pm
Atomic Radius,
non-bonded (Å):
1.92
Covalent Radius: 84±3 pm
Covalent Radius (Å): 0.84
Van der Waals Radius: 192 pm
Oxidation States: 3, 2, 1 (mildly acidic oxide)
Phase: Solid
Crystal Structure: rhombohedral
Magnetic Ordering: diamagnetic
Electron Affinity (kJ·mol-1) 26.98
1st Ionization Energy: 800.64 kJ·mol-1
2nd Ionization Energy: 2427.09 kJ·mol-1
3rd Ionization Energy: 3659.78 kJ·mol-1
CAS Number: 7440-42-8
EC Number: 231-151-2
MDL Number: MFCD00134034
Beilstein Number: N/A
SMILES Identifier: B
InChI Identifier: InChI=1S/B
InChI Key: ZOXJGFHDIHLPTG-UHFFFAOYSA-N
PubChem CID: 5462311
ChemSpider ID: 4575371
Earth - Total: 9.6 ppb
Mercury - Total: 0.11 ppb
Venus - Total: 10.0 ppb
Earth - Seawater (Oceans), ppb by weight: 4440
Earth - Seawater (Oceans), ppb by atoms: 2500
Earth -  Crust (Crustal Rocks), ppb by weight: 8700
Earth -  Crust (Crustal Rocks), ppb by atoms: 17000
Sun - Total, ppb by weight: 2
Sun - Total, ppb by atoms: 0.2
Stream, ppb by weight: 10
Stream, ppb by atoms: 1
Meterorite (Carbonaceous), ppb by weight: 1600
Meterorite (Carbonaceous), ppb by atoms: 3000
Typical Human Body, ppb by weight: 700
Typical Human Body, ppb by atom: 410
Universe, ppb by weight: 1
Universe, ppb by atom: 0.1
Discovered By: Joseph Louis Gay-Lussac and Louis Jacques Thénard
Discovery Date: 1808
First Isolation: Humphry Davy (9 July 1808)

Health, Safety & Transportation Information for Boron

Boron in its elemental form is not toxic. Safety data for Boron and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab. The below information applies to elemental Boron.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Warning
Hazard Statements H302
Hazard Codes Xn
Risk Codes 22
Safety Precautions N/A
RTECS Number ED7350000
Transport Information N/A
WGK Germany 3
Globally Harmonized System of
Classification and Labelling (GHS)
Exclamation Mark-Acute Toxicity

Boron Isotopes

Boron has two stable isotopes: 10B and 11B.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
6B 6.04681(75)# N/A Unknown N/A N/A -0.74 -
7B 7.02992(8) 350(50)E-24 s [1.4(2) ] p to 6Be (3/2-) N/A 23.08 -
8B 8.0246072(11) 770(3) ms EC to 8Be; 4He; EC + 2 α to n 2+ 1.0355 36.1 -
9B 9.0133288(11) 800(300)E-21 s [0.54(21) keV] 2α to 1H; p to 8Be 3/2- 1.8006 54.71 -
10B 10.0129370(4) STABLE - 3+ 1.80065 64 19.9
11B 11.0093054(4) STABLE - 3/2- 2.688637 74.87 80.1
12B 12.0143521(15) 20.20(2) ms β- to 12C; β- + 3α to n 1+ 1.0031 78.29 -
13B 13.0177802(12) 17.33(17) ms β- to 13C; β- + n to 12C 3/2- 3.17778 83.58 -
14B 14.025404(23) 12.5(5) ms β- to 14C; β- + n to 13C 2- N/A 84.2 -
15B 15.031103(24) 9.87(7) ms β- + n to 14C; β- to 15C; β- + 2n to 13C 3/2- N/A 86.69 -
16B 16.03981(6) <190E-12 s [<0.1 ] n to 15B 0- N/A 87.32 -
17B 17.04699(18) 5.08(5) ms β- + n to 16C; β- to 17C; β- + 2n to 15C; β- + 3n to 14C; β- + 4n to 13C (3/2-) N/A 88.87 -
18B 18.05617(86)# >26 ns n to 17B (4-)# N/A 87.64 -
19B 19.06373(43)# 2.92(13) ms β- to 19C (3/2-)# N/A 89.19 -
Boron Elemental Symbol

Recent Research & Development for Boron

  • S.J. Grauer, E.J.F.R. Caron, N.L. Chester, M.A. Wells, K.J. Daun, Investigation of melting in the Al–Si coating of a boron steel sheet by differential scanning calorimetry, Journal of Materials Processing Technology, Volume 216, February 2015
  • Leili Tafaghodi Khajavi, Kazuki Morita, Takeshi Yoshikawa, Mansoor Barati, Thermodynamics of boron distribution in solvent refining of silicon using ferrosilicon alloys, Journal of Alloys and Compounds, Volume 619, 15 January 2015
  • Shigeaki Ono, Kenji Mibe, Naohisa Hirao, Yasuo Ohishi, In situ Raman spectroscopy of cubic boron nitride to 90 GPa and 800 K, Journal of Physics and Chemistry of Solids, Volume 76, January 2015
  • Zhaofu Zhang, Zhaohui Geng, Danyun Cai, Tongxi Pan, Yixin Chen, Liyuan Dong, Tiege Zhou, Structure, electronic and magnetic properties of hexagonal boron nitride sheets doped by 5d transition metal atoms: First-principles calculations and molecular orbital analysis, Physica E: Low-dimensional Systems and Nanostructures, Volume 65, January 2015
  • Zihab Sohbatzadeh, M.R. Roknabadi, Nasser Shahtahmasebi, Mohammad Behdani, Spin-dependent transport properties of an armchair boron-phosphide nanoribbon embedded between two graphene nanoribbon electrodes, Physica E: Low-dimensional Systems and Nanostructures, Volume 65, January 2015
  • B. Podgornik, T. Kosec, A. Kocijan, Č. Donik, Tribological behaviour and lubrication performance of hexagonal boron nitride (h-BN) as a replacement for graphite in aluminium forming, Tribology International, Volume 81, January 2015
  • Jianfeng Wang, Liguo Wang, Shaokang Guan, Shijie Zhu, Ran Li, Tao Zhang, Effects of boron content on the glass-forming ability and mechanical properties of Co–B–Ta glassy alloys, Journal of Alloys and Compounds, Volume 617, 25 December 2014
  • Binhua Chu, Da Li, Kuo Bao, Fubo Tian, Defang Duan, Xiaojing Sha, Pugeng Hou, Yunxian Liu, Huadi Zhang, Bingbing Liu, Tian Cui, Ultrahard boron-rich tantalum boride: Monoclinic TaB4, Journal of Alloys and Compounds, Volume 617, 25 December 2014
  • Shengkui Zhong, Lihua Zhou, Ling Wu, Lianfeng Tang, Qiyi He, Jalal Ahmed, Nitrogen- and boron-co-doped core–shell carbon nanoparticles as efficient metal-free catalysts for oxygen reduction reactions in microbial fuel cells, Journal of Power Sources, Volume 272, 25 December 2014
  • Ling Li, Xichuan Yang, Wenming Zhang, Huayan Zhang, Xiaowei Li, Boron and sulfur co-doped TiO2 nanofilm as effective photoanode for high efficiency CdS quantum-dot-sensitized solar cells, Journal of Power Sources, Volume 272, 25 December 2014