1. Nitrogen (N2): Around 78% of the atmosphere.

2. Oxygen (O2): Around 21% of the atmosphere.

3. Argon (Ar): About 0.93% of the atmosphere.

4. Carbon Dioxide (CO2): Around 0.04% of the atmosphere, but it's a very important greenhouse gas.

While these are the four major components, there are many trace gases in the atmosphere as well, such as neon, helium, methane, and ozone.