Quick Facts
| Property | Value |
|---|---|
| Symbol | B |
| Atomic Number | 5 |
| Atomic Mass | 10.81 u |
| Category | Metalloid |
| Period | 2 |
| Group | 13 |
| Block | p |
| Electron Configuration | [He] 2s² 2p¹ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 2.34 g/cm³ |
| Melting Point | 2077°C (2350 K) |
| Boiling Point | 4000°C (4273 K) |
| Appearance | Black-brown crystalline solid |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [He] 2s² 2p¹ |
| Electronegativity | 2.04 (Pauling scale) |
| First Ionization Energy | 800.6 kJ/mol |
| Atomic Radius | 90 pm |
| Covalent Radius | 84 pm |
| Van der Waals Radius | 192 pm |
History and Discovery
Discovered by: Joseph Louis Gay-Lussac, Louis Jacques Thénard, and Humphry Davy Year of Discovery: 1808 Location: France and England
Etymology
The name "boron" comes from "borax," the mineral from which it was first isolated, combined with the suffix "-on" from "carbon." The word borax itself derives from Arabic "būraq" and Persian "būrah."
Discovery Story
Boron was isolated independently in 1808 by two teams: Joseph Louis Gay-Lussac and Louis Jacques Thénard in Paris, and Humphry Davy in London. Both teams heated boric acid with potassium to produce impure boron. Pure boron (over 99%) was not produced until 1909 by Ezekiel Weintraub through reduction of boron halides with hydrogen.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ¹⁰B | 19.9% | Stable | - |
| ¹¹B | 80.1% | Stable | - |
Occurrence
Natural Abundance
Boron comprises about 10 ppm of the Earth's crust. It is never found free in nature but occurs in borates such as borax (sodium tetraborate), kernite, colemanite, and ulexite. Major deposits are found in Turkey (largest producer), the United States (California), Argentina, Chile, and Russia.
Extraction and Production
- From Borax: Reduction of boric oxide (B₂O₃) with magnesium
- High Purity: Decomposition of boron halides on hot filaments
- Sources: Borax mining and extraction from brine deposits
- Turkey controls over 70% of global boron reserves
Applications and Uses
Industrial Applications
- Borosilicate glass (Pyrex) for laboratory equipment and cookware
- Fiberglass insulation
- Laundry bleach (sodium perborate)
- Ceramic glazes and enamels
Technological Applications
- Boron carbide (extremely hard material) for armor and abrasives
- Boron fiber composites in aerospace
- Neutron absorber in nuclear reactors (boron-10)
- Semiconductors (boron doping)
Agricultural Applications
- Essential micronutrient in fertilizers
- Boric acid as insecticide
Other Uses
- Pyrotechnics (green flames)
- High-strength magnets (neodymium-iron-boron)
- Sports equipment (tennis rackets, golf clubs)
Biological Role
Boron is an essential trace element for plants and possibly for animals and humans.
In Plants
- Essential for cell wall formation
- Important for fruit and seed development
- Involved in sugar transport
In the Human Body
- May play a role in bone metabolism
- Possible influence on hormone levels
- Dietary intake typically 1-3 mg/day
- Not officially classified as essential for humans
Dietary Sources
Fruits, vegetables (especially leafy greens), nuts, and legumes are rich in boron.
Safety and Hazards
Toxicity
Boron compounds have relatively low toxicity. Boric acid has been used medicinally and as a mild antiseptic. However, excessive intake can cause gastrointestinal disturbance and, in extreme cases, affects the reproductive system.
Handling Precautions
- Pure boron dust can be irritating to eyes and respiratory system
- Boric acid should be kept away from children and pets
- Boron hydrides (boranes) are highly toxic and flammable
- Use standard industrial hygiene practices
Environmental Impact
Boron is naturally occurring and generally does not accumulate in the food chain. High concentrations in water can be toxic to plants.
Interesting Facts
- Boron carbide is one of the hardest materials known, used in tank armor
- Boron-10 is excellent at absorbing neutrons, making it crucial for nuclear reactor control
- The borosilicate glass Pyrex was invented in 1915 and revolutionized laboratory and kitchen glassware
- Boron compounds have been used as mild antiseptics since the 1800s
- Boron is formed entirely by cosmic ray spallation and not by stellar nucleosynthesis