The Earth's atmosphere is a complex mixture of gases that surrounds the planet. At sea level, the atmosphere is composed of the following gases:

* Nitrogen (N2): 78.08%

* Oxygen (O2): 20.95%

* Argon (Ar): 0.93%

* Carbon dioxide (CO2): 0.04%

* Neon (Ne): 0.0018%

* Helium (He): 0.0005%

* Methane (CH4): 0.0002%

* Krypton (Kr): 0.0001%

* Hydrogen (H2): 0.00005%

In addition to these gases, the atmosphere also contains trace amounts of other compounds, including water vapor, ozone (O3), and various pollutants such as dust, smoke, and industrial emissions. The composition of the atmosphere can vary slightly from place to place and over time, but these figures represent the average composition at sea level.

Note: The percentages given here are by volume.