Nitrogen (N) – An Essential Element for Life and the Atmosphere
1. General Information
- Symbol: N
- Atomic Number: 7
- Atomic Mass: 14.01 u
- Group: 15 (Pnictogens)
- Period: 2
- Block: p-block
- Electron Configuration: 1s² 2s² 2p³
- Valence Electrons: 5
- Phase at Room Temperature: Gas
2. Isotopes of Nitrogen
| Isotope |
Protons |
Neutrons |
Abundance |
Notes |
| ¹⁴N |
7 |
7 |
99.6% |
Stable and most common. |
| ¹⁵N |
7 |
8 |
0.4% |
Stable, used in research. |
3. Physical Properties
- Color: Colorless
- Odor: Odorless
- Density: 1.25 g/L (at STP)
- Melting Point: -210°C (63 K)
- Boiling Point: -195.8°C (77 K)
- State at STP: Gas
- Non-Metallic and Diatomic: Exists as N₂ molecules.
4. Chemical Properties
- Inert at Room Temperature – Highly stable and unreactive due to the triple bond in N₂ (N≡N).
- Reacts at High Temperatures: Combines with hydrogen, oxygen, and metals.
- Essential for Proteins and DNA.
- Forms:
- Ammonia (NH₃)
- Nitric acid (HNO₃)
- Nitrates (NO₃⁻)
Reaction with Hydrogen (Haber Process):
N₂ + 3H₂ → 2NH₃ (Ammonia)
5. Occurrence and Abundance
- Most abundant gas in Earth’s atmosphere – 78% by volume.
- Found in:
- Organic Matter – Proteins and nucleic acids.
- Soil and Water – As nitrates and ammonia.
- Stars and Interstellar Space – In cosmic dust and gases.
6. The Nitrogen Cycle
- Essential for Ecosystems – Nitrogen is cycled between the atmosphere, soil, and living organisms.
- Stages:
- Nitrogen Fixation: N₂ → NH₃ (by bacteria or lightning).
- Nitrification: NH₃ → NO₃⁻ (nitrates by bacteria).
- Assimilation: Plants absorb nitrates to form proteins.
- Denitrification: NO₃⁻ → N₂ (returns to atmosphere).
7. Industrial Production of Nitrogen
- Fractional Distillation: Extracted from liquid air.
- Haber Process: Produces ammonia by reacting nitrogen with hydrogen at high pressure and temperature.
8. Uses of Nitrogen
| Application |
Description |
| Fertilizers |
Ammonia and nitrates boost plant growth. |
| Cryogenics |
Liquid nitrogen cools medical and industrial equipment. |
| Food Preservation |
Inert atmosphere prevents spoilage. |
| Electronics |
Nitrogen is used to prevent oxidation. |
| Medical |
Used in pharmaceuticals and freezing tissues. |
| Explosives |
Nitrogen compounds like TNT and nitroglycerin. |
| Welding and Metal Cutting |
Provides an inert atmosphere. |
9. Important Nitrogen Compounds
| Compound |
Formula |
Use |
| Ammonia |
NH₃ |
Fertilizers, cleaners, refrigerants. |
| Nitric Acid |
HNO₃ |
Explosives, fertilizers. |
| Nitrogen Dioxide |
NO₂ |
Air pollutant, precursor to acid rain. |
| Nitrous Oxide |
N₂O |
Anesthetic (laughing gas). |
| Nitrates |
NO₃⁻ |
Fertilizers, preservatives. |
10. Biological Importance of Nitrogen
- Essential for Life: A key element in amino acids, proteins, and nucleic acids (DNA and RNA).
- Nitrogen Fixation: Bacteria convert atmospheric nitrogen into usable forms for plants.
- Protein Synthesis: Nitrogen is crucial for the growth and repair of cells.
11. Safety and Toxicity
- Inert Gas Asphyxiation: Displaces oxygen, posing asphyxiation risks in confined spaces.
- Nitrogen Dioxide (NO₂): Toxic and can cause respiratory problems.
- Liquid Nitrogen: Can cause severe frostbite upon contact.
Fun Facts About Nitrogen:
- Nitrogen gas is colorless, odorless, and tasteless.
- Liquid nitrogen can freeze objects instantly.
- Lightning naturally fixes nitrogen by converting N₂ into nitrates.
- DNA, proteins, and chlorophyll all contain nitrogen.