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1. General Information
- Symbol: O
- Atomic Number: 8
- Atomic Mass: 15.999 u
- Group: 16 (Chalcogens)
- Period: 2
- Block: p-block
- Electron Configuration: 1s² 2s² 2p⁴
- Valence Electrons: 6
- Phase at Room Temperature: Gas
2. Isotopes of Oxygen
Isotope | Protons | Neutrons | Abundance | Notes |
---|---|---|---|---|
¹⁶O | 8 | 8 | 99.76% | Stable and most abundant. |
¹⁷O | 8 | 9 | 0.04% | Stable, used in research. |
¹⁸O | 8 | 10 | 0.20% | Stable, used in paleoclimate studies. |
3. Physical Properties
- Color: Colorless
- Odor: Odorless
- Density: 1.429 g/L (at STP)
- Melting Point: -218.8°C
- Boiling Point: -183.0°C
- State at STP: Gas
- Form: Diatomic molecule (O₂)
4. Chemical Properties
- Highly Reactive – Supports combustion and combines readily with most elements.
- Oxidizer: Causes other substances to burn.
- Forms Oxides: Combines with metals and non-metals to form oxides.
- Allotropes:
- O₂ (Molecular Oxygen): Essential for life and respiration.
- O₃ (Ozone): Protects Earth from UV radiation.
Combustion Reaction:
C + O₂ → CO₂ (Carbon Dioxide) 4Fe + 3O₂ → 2Fe₂O₃ (Rust)
5. Occurrence and Abundance
- Third most abundant element in the universe.
- On Earth:
- Atmosphere: 21% by volume.
- Crust: 46% (in oxides and silicates).
- Oceans: 85% (in water molecules).
- Living Organisms: Component of water, proteins, and DNA.
6. Industrial Production of Oxygen
- Fractional Distillation: Separation from liquid air.
- Electrolysis of Water: Splitting H₂O into hydrogen and oxygen.
- Chemical Methods: Decomposition of hydrogen peroxide (H₂O₂).
7. Uses of Oxygen
Application | Description |
---|---|
Respiration and Medicine | Life support in hospitals and oxygen tanks. |
Combustion and Energy | Supports burning of fuels in engines and rockets. |
Steel Production | Used to remove impurities from molten iron. |
Water Treatment | Ozone (O₃) purifies and disinfects water. |
Chemical Industry | Oxidizer in the production of chemicals. |
Spacecraft and Aviation | Breathing systems and fuel oxidizer. |
8. Oxygen Compounds
Compound | Formula | Use |
---|---|---|
Water | H₂O | Essential for all known life forms. |
Carbon Dioxide | CO₂ | Photosynthesis, respiration. |
Ozone | O₃ | Protects Earth from UV radiation. |
Iron Oxide (Rust) | Fe₂O₃ | Corrosion product of iron. |
Silicon Dioxide | SiO₂ | Glass, sand, and ceramics. |
9. Biological Importance of Oxygen
- Essential for Cellular Respiration:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)
- Photosynthesis:
- Plants produce oxygen by splitting water during photosynthesis.
6CO₂ + 6H₂O + Light → C₆H₁₂O₆ + 6O₂
- Component of Water and Organic Molecules – Crucial for life processes.
10. The Ozone Layer (O₃)
- Formation:
O₂ + UV → 2O → O₂ + O → O₃
- Protects Earth by absorbing harmful UV radiation.
- Depletion:
- Caused by CFCs (chlorofluorocarbons), leading to environmental concerns.
11. Safety and Hazards
- Supports Combustion: Increases fire risk in high concentrations.
- Oxygen Toxicity: Breathing pure oxygen at high pressures can cause lung damage.
- Cryogenic Burns: Liquid oxygen can cause severe frostbite.
Fun Facts About Oxygen:
- Oxygen makes up 65% of the human body by mass (mostly in water).
- The blue color of the sky is due to oxygen and nitrogen scattering sunlight.
- Fish extract oxygen from water using gills.
- Oxygen was discovered independently by Carl Wilhelm Scheele and Joseph Priestley in the 18th century.