Boron
Boron is a hard, brittle metalloid that sits between the metals and nonmetals in both properties and behavior. It's never found as a free element in nature, occurring instead in borate minerals like borax, and its compounds show up everywhere from heat-resistant glass to laundry detergent.
- Group · Period
- 13 · 2
- At room temp
- solid
- Melts at
- 2348 K
- Density
- 2.37 g/cm³
- Discovered
- 1808
Uses
Boron compounds are widely used in glassmaking — borosilicate glass, used for laboratory glassware and ovenware, resists thermal shock far better than standard glass because of the boron oxide mixed into it. Boron-containing fiberglass insulation and specialty ceramics rely on similar properties. Borates are also a common ingredient in detergents and cleaning products, where they help boost cleaning power and act as a mild bleaching agent.
In its harder forms, boron takes on a very different role: boron carbide is one of the hardest materials known, used in armor plating and abrasive tools, and boron compounds are used to make the strong, lightweight fibers found in some high-performance sporting equipment and aerospace composites. Boron is also added in tiny amounts to fertilizers, since plants need it in small quantities to grow properly.
History
Boron was isolated in 1808, nearly simultaneously by two separate teams: French chemists Joseph Louis Gay-Lussac and Louis Jacques Thénard in Paris, and English chemist Humphry Davy in London, both working from the mineral borax. The samples each team produced were still fairly impure, and it took much more work by later chemists to obtain boron in a purer, well-defined form. Its name comes directly from borax, the mineral from which it was first extracted.
Fun facts
- Boron is essential for healthy plant growth as a micronutrient, even though it isn't considered essential for human health in the same way.
- Borosilicate glass, best known by the brand name Pyrex, contains boron oxide, which gives it much better resistance to cracking under sudden temperature changes than ordinary glass.
- Boron carbide is one of the hardest known materials, hard enough to be used in bulletproof vests and tank armor.
Frequently asked questions
Is boron a metal or a nonmetal?
Neither cleanly — boron is classified as a metalloid, meaning it shares properties with both groups. It's a poor electrical conductor like a nonmetal but has some structural and chemical similarities to metals, which is why it sits on the dividing line of the periodic table.
What is borax actually used for?
Borax is a naturally occurring boron mineral used in laundry detergents as a cleaning booster, as a flux in metalworking to help solder flow smoothly, and as a raw ingredient in manufacturing glass and ceramics.
Why does adding boron make glass more heat resistant?
Boron oxide lowers the glass's coefficient of thermal expansion, meaning it expands and contracts less as temperature changes. That reduces the internal stress that causes ordinary glass to crack when it's heated or cooled quickly, which is exactly why borosilicate glassware can go from an oven straight into cold water.
Compounds
5 notable compounds containing B
- Na2B4O7·10H2Omineral
Borax
A hydrated sodium borate mineral built from linked boron-oxygen rings, crystallizing naturally as soft, colorless crystals in dry lakebeds.
Used for: Laundry booster, metalworking flux, glass and ceramic glazes
- H3BO3acid
Boric acid
A weak acid made of flat, triangular molecules that stack together through hydrogen bonding into soft, flaky white crystals.
Used for: Antiseptic, insecticide, eye-wash solutions, glass manufacturing
- BNindustrial
Boron nitride
Isoelectronic with carbon, it forms a slippery hexagonal layered structure like graphite, or an extremely hard cubic form comparable to diamond.
Used for: High-temperature lubricant, cutting tools, heat-resistant coatings
- B2O3oxide
Boron trioxide
A glass-forming oxide that readily solidifies into an amorphous network rather than an ordered crystal lattice.
Used for: Key ingredient in borosilicate glass and fiberglass
- Nd2Fe14Bindustrial
Neodymium iron boron
An intermetallic compound whose tetragonal crystal structure produces the strongest permanent magnets commercially available, far outperforming older ferrite and alnico magnets.
Used for: Permanent magnets in electric motors, headphones, and hard drives
Isotopes
15 known isotopes
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| Isotope | Natural abundance | Half-life | Decay mode | Mass excess | Binding energy / nucleon | Decay width |
|---|---|---|---|---|---|---|
| B-10 stable | 19.65% | Stable | — | 12,050.61 keV | 6,475.08 keV | — |
| B-11 stable | 80.35% | Stable | — | 8,667.71 keV | 6,927.73 keV | — |
Show all 15 isotopes
| B-7 | — | 801 keV | Proton emission (100%) | 27,676.55 keV | 3,558.71 keV | 8.01 × 105 eV |
| B-8 | — | 770 ms | Electron capture / beta-plus decay (100%), Beta-plus, alpha emission (100%) | 22,921.57 keV | 4,717.16 keV | 5.93 × 10-16 eV |
| B-9 | — | 0.54 keV | Proton emission (100%) | 12,416.49 keV | 6,257.07 keV | 5.40 × 102 eV |
| B-12 | — | 20.20 ms | Beta-minus decay (100%), Beta-minus, alpha emission (0.6%) | 13,369.4 keV | 6,631.22 keV | 2.26 × 10-14 eV |
| B-13 | — | 17.33 ms | Beta-minus decay (100%), Beta-minus, neutron emission (0.286%) | 16,561.95 keV | 6,496.42 keV | 2.63 × 10-14 eV |
| B-14 | — | 12.5 ms | Beta-minus decay (100%), Beta-minus, neutron emission (6.1%) | 23,663.69 keV | 6,101.65 keV | 3.65 × 10-14 eV |
| B-15 | — | 9.93 ms | Beta-minus decay (100%), Beta-minus, neutron emission (99.68%) | 28,957.38 keV | 5,880.04 keV | 4.59 × 10-14 eV |
| B-16 | — | 100 keV | Neutron emission (100%) | 37,111.7 keV | 5,507.35 keV | 1.00 × 105 eV |
| B-17 | — | 5.08 ms | Beta-minus decay (100%), Beta-minus, neutron emission (63%), B-2N (11%) | 43,716.32 keV | 5,269.67 keV | 8.98 × 10-14 eV |
| B-18 | — | — | Neutron emission (100%) | 51,792.64 keV | 4,976.63 keV | — |
| B-19 | — | 2.92 ms | Beta-minus decay (100%), Beta-minus, neutron emission (71.8%), B-2N (16%) | 59,770.25 keV | 4,719.63 keV | 1.56 × 10-13 eV |
| B-20 | — | 500 keV | Neutron emission (100%) | 69,401.57 keV | 4,405.65 keV | 5.00 × 105 eV |
| B-21 | — | 600 keV | Two-neutron emission (100%) | 78,382.89 keV | 4,152.53 keV | 6.00 × 105 eV |