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Helium (He) – The Lightest Noble Gas and the Second Most Abundant Element in the Universe
1. General Information
- Symbol: He
- Atomic Number: 2
- Atomic Mass: 4.0026 u
- Group: 18 (Noble Gases)
- Period: 1
- Block: s-block
- Electron Configuration: 1s²
- Valence Electrons: 2
- Phase at Room Temperature: Gas
2. Isotopes of Helium
| Isotope | Protons | Neutrons | Abundance |
|---|---|---|---|
| ³He | 2 | 1 | Trace (Rare) |
| ⁴He | 2 | 2 | 99.999% |
- ⁴He is produced by nuclear fusion in stars and during the radioactive decay of heavy elements (alpha decay).
3. Physical Properties
- Color: Colorless
- Odor: Odorless
- Density: 0.1786 g/L (at STP)
- Melting Point: Does not solidify at standard pressure.
- Boiling Point: -268.93°C (4.2 K)
- State at STP: Gas
- Inert and Non-Flammable – Helium does not readily react with other elements.
4. Chemical Properties
- Inert: Helium is part of the noble gases and is chemically non-reactive.
- Non-Toxic and Non-Flammable – Safe to use in various applications.
- Monoatomic Gas (He): Helium exists as single atoms under normal conditions.
5. Occurrence and Abundance
- Second most abundant element in the universe (after hydrogen).
- On Earth:
- Found in natural gas deposits.
- Formed through alpha particle decay of radioactive elements in the Earth’s crust.
- Extracted by fractional distillation of liquefied natural gas (LNG).
6. Production and Extraction
| Method | Description |
|---|---|
| Fractional Distillation | Extracted from natural gas where helium is concentrated. |
| Nuclear Reactions | Produced as a byproduct of radioactive decay (alpha decay). |
| Star Fusion | Created in massive quantities in stars through nuclear fusion. |
7. Uses of Helium
| Application | Description |
|---|---|
| Cryogenics | Cooling superconducting magnets (e.g., MRI machines). |
| Balloons and Blimps | Non-flammable and lighter than air. |
| Pressurizing Agent | Used in rocket fuel tanks. |
| Diving and Breathing Mixtures | Heliox (Helium + Oxygen) prevents nitrogen narcosis. |
| Electronics and Fiber Optics | Used to create inert atmospheres. |
| Scientific Research | Superfluid studies at near absolute zero. |
| Welding | Inert gas for arc welding. |
8. Unique Properties of Helium
- Lowest Boiling Point of Any Element: 4.2 K (-268.93°C).
- Cannot Solidify at Normal Pressure: Even at absolute zero, helium remains a liquid unless under high pressure.
- Superfluid Helium (²He): Helium exhibits zero viscosity at temperatures near absolute zero, allowing it to flow without friction.
- Second Lightest Element – Only hydrogen is lighter.
9. Helium and Space Exploration
- Rocket Fuel Purge: Helium is used to pressurize and purge fuel tanks in rockets.
- Cooling Systems: Essential for cooling space instruments and satellites.
- Balloon Flights: Used for high-altitude weather balloons.
10. Safety and Handling
- Non-Toxic and Safe to Inhale in Small Quantities – But excessive inhalation displaces oxygen, causing suffocation.
- Asphyxiation Risk: In confined spaces, helium can cause oxygen displacement.
- Storage: Stored in pressurized cylinders and cryogenic tanks.
Fun Facts About Helium:
- Helium was discovered on the Sun before being found on Earth (spectroscopy in 1868).
- Helium makes your voice high-pitched because it travels faster through the vocal cords.
- Stars constantly produce helium through nuclear fusion, turning hydrogen into helium.