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Boron (B) – A Versatile Metalloid Essential for Industrial and Biological Applications
1. General Information
- Symbol: B
- Atomic Number: 5
- Atomic Mass: 10.81 u
- Group: 13 (Metalloids)
- Period: 2
- Block: p-block
- Electron Configuration: 1s² 2s² 2p¹
- Valence Electrons: 3
- Phase at Room Temperature: Solid
2. Isotopes of Boron
| Isotope | Protons | Neutrons | Abundance |
|---|---|---|---|
| ¹⁰B | 5 | 5 | 19.9% |
| ¹¹B | 5 | 6 | 80.1% |
- ¹⁰B is important for nuclear shielding due to its ability to absorb neutrons.
3. Physical Properties
- Color: Black (Crystalline) or Brown (Amorphous)
- Density: 2.34 g/cm³
- Melting Point: 2,076°C
- Boiling Point: 3,927°C
- State at STP: Solid
- Hardness: Second hardest element (next to diamond, in crystalline form).
4. Chemical Properties
- Reacts with Oxygen: Forms boron oxide (B₂O₃) at high temperatures.
- Inert at Room Temperature – Does not react easily with air or water.
- Combines with Metals – Forms borides, which are extremely hard.
- Forms Covalent Compounds – Such as boric acid (H₃BO₃) and borates.
Reaction with Oxygen:
4B + 3O₂ → 2B₂O₃
5. Occurrence and Abundance
- Rare in Earth’s Crust: 0.001% by weight.
- Found in:
- Borax (Na₂B₄O₇·10H₂O)
- Kernite (Na₂B₄O₆(OH)₂·3H₂O)
- Tourmaline (Borosilicate mineral)
- Largest Deposits: Turkey, USA, and South America.
6. Production and Extraction
| Source | Method |
|---|---|
| Borax and Kernite | Dissolved in water and refined to boric acid. |
| Electrolysis | Produces pure boron from boron halides. |
7. Uses of Boron
| Application | Description |
|---|---|
| Glass and Ceramics | Borosilicate glass (heat-resistant). |
| Detergents | Borax is a key ingredient in cleaning products. |
| Fertilizers | Boron is essential for plant growth. |
| Nuclear Reactors | ¹⁰B absorbs neutrons, preventing radiation. |
| Aerospace and Defense | Boron fibers reinforce aircraft and armor. |
| Medicinal Uses | Boric acid is used as an antiseptic. |
| Semiconductors | Boron is used to dope silicon in electronics. |
8. Unique Properties of Boron
- Metalloid: Exhibits properties of both metals and non-metals.
- Extreme Hardness: Crystalline boron is as hard as diamond.
- Neutron Absorption: Essential for nuclear technology.
- Lightweight and Strong: Used in high-strength materials and aerospace.
9. Boron Compounds
| Compound | Formula | Use |
|---|---|---|
| Boric Acid | H₃BO₃ | Antiseptic, insecticide, eyewash. |
| Borax | Na₂B₄O₇·10H₂O | Detergents, ceramics, glass. |
| Boron Nitride | BN | Lubricants, coatings, cutting tools. |
| Boron Carbide | B₄C | Armor, bulletproof vests. |
| Boron Trifluoride | BF₃ | Catalyst in organic reactions. |
10. Biological Importance
- Essential for Plants: Boron helps in cell wall formation and pollination.
- Trace Element for Humans: Supports bone health, but excess can be toxic.
- Deficiency in Plants: Leads to poor growth and weak cell walls.
11. Boron in Technology
- Boron Fibers: Lightweight and used in aerospace.
- Doping Agent: Used in semiconductors to alter electrical properties.
- Boron Alloys: Used in lightweight, high-strength materials.
12. Safety and Toxicity
- Low Toxicity in Small Amounts: Essential for plants and trace for humans.
- Toxic in High Doses: Can cause nausea, vomiting, and skin irritation.
- Inhalation Risk: Boron dust can irritate the respiratory system.
Fun Facts About Boron:
- Boron is found in stars and is created by cosmic ray spallation.
- Borosilicate glass (Pyrex) resists heat and thermal shock.
- Tourmaline gemstones contain boron and are prized for their colors.
- The hardness of boron carbide makes it the material of choice for tank armor and bulletproof vests