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
10. The Ozone Layer (O₃)
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.