Periodic Table

Boron

Metalloid

Quick Facts about Boron

Be
  • solid- state of matter at room temperature
  • Stable- has at least one stable isotope
  • +3- common oxidation states in compounds
  • TET- crystal structure, atomic arrangement in solid form
C

Boron (B) is element 5 on the periodic table. Atomic mass of B: 10.8100 u. B is in period 2, group 13. Melting point of B: 2349.00 K.Density of B: 2.34 g/cm³.

Why Boron Matters

Boron in everyday life and industry

In Your Home

  • Borosilicate glass (Pyrex) resists thermal shock in cookware and lab equipment
  • Borax is a common laundry booster and cleaning agent
  • Fiberglass insulation contains boron compounds

Industry Uses

DefenseBoron carbide is used in tank armor and bulletproof vests

In Your Body

✓ Essential for life

Boron is essential for plants - required for cell wall formation Humans need trace amounts of boron for bone health Boric acid has antiseptic and antifungal properties Boron deficiency in plants causes hollow stems and poor fruit development

Safety: No significant toxicity data for Boron.

Discovery of Boron

Discovered by Sir H. Davy, J.L. Gay-Lussac, L.J. Thénard in England/France, 1808

Name origin: From Arabic and Persian words for borax.

History & Events

1808
Name comes from Arabic 'buraq' or Persian 'burah' for borax
1808
Borax has been used since ancient times for gold refining and glassmaking
1808
Pure boron wasn't isolated until 1808-1809 by multiple chemists
1808
20 Mule Team Borax became famous through Death Valley advertising

About Boron

An element of group 13 of the periodic table. There are two allotropes, amorphous boron is a brown powder, 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 Properties of B

Atomic Number of B
5
Atomic Mass of B
10.8100 u
Electron Configuration
[He] 2s2 2p1
Electronegativity
2.04
Block
p-block
Group
13
Period
2

Physical Properties of B

Phase (STP)
solid
Melting Point of B
2349.00 K
Boiling Point of B
4200.00 K
Density of B
2.3400 g/cm3

Thermal Properties

Heat of Fusion
23.60 kJ/mol
Heat of Vaporization
504.50 kJ/mol
Specific Heat
1.03 J/g·K
Molar Heat Capacity
11.09 J/mol·K
Thermal Conductivity
27.40 W/m·K

Atomic Radii

Calculated
85 pm
Covalent
85 pm
Van der Waals
192 pm
Metallic
80 pm

Common Misconceptions

Wrong:Borax and boric acid are the same thing.
Correct:They are different compounds: borax is sodium borate (Na2B4O7·10H2O), while boric acid is H3BO3.
Wrong:Boron is a metal.
Correct:It's a metalloid with properties between metals and nonmetals
Wrong:Boric acid is safe to ingest because it's used in eyewash products.
Correct:Boric acid is toxic if ingested. Dilute solutions are safe for external use as eyewash, but ingestion can cause nausea, vomiting, and serious harm.

Allotropes of Boron

Boron exists in 2 different structural forms (allotropes), each with unique properties.

Amorphous Boron

Brown powder form, less pure, used industrially

Structure:Non-crystalline
Properties:Reactive, lower hardness than crystalline forms

Crystalline Boron

Black, metallic appearance with extreme hardness

Structure:Icosahedral B12 units
Properties:9.3 Mohs hardness, semiconductor at room temperature

Isotopes of Boron

Boron has 2 naturally occurring isotopes.

IsotopeAtomic Mass (u)AbundanceHalf-LifeDecay Mode
105B (B-10)Boron-10 isotope10.0129369519.90%
115B (B-11)Boron-11 isotope11.0093053680.10%

Data source: NIH PubChem (aggregated from IUPAC, NIST)

Isotope Applications

Isotopes of Boron have important real-world applications in science and industry.

Industrial Applications

The large value of the absorption cross section of 10B for thermal neutrons makes this isotope useful for counting neutrons. 10B is being studied as a potential replacement for 3He in radiation detectors [32], [53], [54]. The large thermal absorption cross section of 10B makes the isotope useful in control rods (Fig. IUPAC.5.2) [55].

Medical Applications

10B has a high thermal neutron absorption cross section and can readily absorb neutrons via the reaction 10B+n→ 7Li+α. The alpha particles resulting from this reaction carry away a relatively large kinetic energy and are useful for the treatment of malignant tumors in cancer patients [56], [57], [58].

Abundance

Earth's Crust
10.0 mg/kg
Seawater
4.4 mg/L

Uses

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).

Geochemistry

Goldschmidt
litophile

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