The composition of air: Nitrogen 78%, Oxygen 21%, Carbon Dioxide (CO2) 0.04%

The composition of Earth’s atmosphere consists primarily of the following gases:

1. Nitrogen (N₂) – 78.08%
• The most abundant gas in the atmosphere. It is largely inert and does not readily react with other substances under normal conditions.
2. Oxygen (O₂) – 20.95%
• Essential for respiration in humans and animals, and crucial for combustion processes.
3. Argon (Ar) – 0.93%
• A noble gas that is chemically inert and used in applications like welding and lighting.
4. Carbon Dioxide (CO₂) – 0.04% (approximately 400 ppm)
• A greenhouse gas essential for plant photosynthesis but also a contributor to climate change when present in excess.

Variable Components in Air:

In addition to the above gases, air also contains variable amounts of:
• Water Vapor (H₂O) – Can range from 0% to 4%, depending on location and weather conditions.
• Ozone (O₃) – A small but critical component, concentrated in the stratosphere to protect against ultraviolet radiation.
• Aerosols – Tiny particles such as dust, pollen, soot, and pollutants.
This composition remains relatively constant up to about 10,000 meters (33,000 feet) but can vary due to pollution, weather patterns, and geographical factors.