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Hydrogen (H) – The Lightest and Most Abundant Element in the Universe
1. General Information
- Symbol: H
- Atomic Number: 1
- Atomic Mass: 1.008 u
- Group: 1 (Non-metal)
- Period: 1
- Block: s-block
- Electron Configuration: 1s¹
- Valence Electrons: 1
- Phase at Room Temperature: Gas
2. Isotopes of Hydrogen
| Isotope | Protons | Neutrons | Name | Abundance |
|---|---|---|---|---|
| ¹H | 1 | 0 | Protium | 99.98% |
| ²H | 1 | 1 | Deuterium (²H or D) | 0.02% |
| ³H | 1 | 2 | Tritium (³H or T) | Trace |
3. Physical Properties
- Color: Colorless
- Odor: Odorless
- Density: 0.08988 g/L (at 0°C and 1 atm)
- Melting Point: -259.16°C
- Boiling Point: -252.87°C
- State at STP: Gas
4. Chemical Properties
- Highly reactive – Readily forms compounds with most elements.
- Diatomic Molecule (H₂): Exists as H₂ gas under standard conditions.
- Flammable – Combines explosively with oxygen to form water (H₂O).
- Reacts with Non-metals – Forms acids (e.g., HCl) when combined with halogens.
- Reduces Metal Oxides – Can extract metals from ores.
Combustion Reaction (Hydrogen + Oxygen):
2H₂ + O₂ → 2H₂O + Energy
5. Occurrence and Abundance
- Most abundant element in the universe (about 75% by mass).
- On Earth:
- Exists in water (H₂O).
- Found in organic compounds, hydrocarbons, and fossil fuels.
- Present in stars and the Sun (nuclear fusion).
6. Production Methods
| Method | Description |
|---|---|
| Steam Reforming | CH₄ + H₂O → CO + 3H₂ (from methane) |
| Electrolysis of Water | 2H₂O → 2H₂ + O₂ (splitting water using electricity) |
| Biological Processes | Hydrogen from algae or bacteria. |
| Gasification | From coal or biomass. |
7. Uses of Hydrogen
| Application | Description |
|---|---|
| Fuel | Hydrogen fuel cells (H₂ + O₂ → Electricity + H₂O) |
| Industrial | Production of ammonia (Haber Process). |
| Rocket Fuel | Used in liquid form for rocket propulsion. |
| Chemical Feedstock | Used to refine petroleum and in metallurgy. |
| Welding | Hydrogen is used in oxyhydrogen torches. |
| Cooling | Used as a coolant in power plants. |
8. Hydrogen as a Fuel
- Hydrogen Fuel Cells – Generate electricity by combining hydrogen and oxygen.
- Eco-Friendly – Only by-product is water.
- Challenges:
- Storage (requires high-pressure tanks or liquefaction).
- Infrastructure (limited hydrogen fueling stations).
- Production can be energy-intensive.
9. Hydrogen Bonding
- Definition: Attraction between hydrogen and electronegative atoms (O, N, F).
- Example: Hydrogen bonding in water (H₂O), contributing to high boiling point and surface tension.
10. Role in the Universe
- Stars and Fusion:
- Hydrogen nuclei fuse to form helium in stars, releasing energy (nuclear fusion).
- The Sun’s energy comes from hydrogen fusion.
- Building Block of Life:
- Essential in organic molecules (proteins, DNA, carbohydrates).
11. Safety and Handling
- Highly Flammable – Handle with caution.
- Explosive Limits in Air: 4% to 75% by volume.
- Storage: Stored in pressurized tanks or as a liquid at very low temperatures.
Fun Facts About Hydrogen:
- Hydrogen is the simplest element – One proton, one electron.
- The hydrogen atom is the only element whose energy levels are described exactly by quantum mechanics.
- Hydrogen fuel cells powered the Apollo missions to the Moon.