Nitrogen
Explanation
The Earth's atmosphere consists of a mixture of gases, water vapour, and particulate matter. The composition of dry air in the lower atmosphere is relatively constant by volume.Composition of the Atmosphere:
- Nitrogen (N2): It is the most abundant gas, constituting approximately 78.08% of the atmosphere by volume. It is relatively inert and acts as a diluent for oxygen.
- Oxygen (O2): It is the second major constituent, accounting for about 20.95%. It is vital for respiration and combustion.
- Argon (Ar): This inert gas is the third most abundant, making up approximately 0.93%.
- Carbon Dioxide (CO2): It constitutes a minor fraction, roughly 0.036% (variable), but plays a critical role in the greenhouse effect and photosynthesis.
Key Takeaway: Nitrogen is the primary constituent of the Earth's atmosphere, followed by Oxygen, Argon, and Carbon Dioxide in descending order of percentage by volume.