The most abundant gas in Earth’s atmosphere is Nitrogen (78% of the atmosphere), followed by Oxygen (21%), the gas we need to live, which is also needed to burn wood and fuel.
The third-most abundant gas is Argon (0.93%).
The fourth most abundant gas is Carbon Dioxide ... the amount in the atmosphere is very small, making up just 0.04% of the atmosphere, but it is very important because plants use it to make simple sugars.
Another important gas is water vapor, which condenses in the atmosphere to form clouds and then rain.
The atmosphere also holds trace amounts of Neon, Helium, Methane, Krypton and Hydrogen.