most abundant gas in earth's atmosphere
The answer depends on the region of the atmosphere and other factors, since the chemical composition of the Earth's atmosphere depends on temperature, altitude, and proximity to water. 1  Usually, the 4 most abundant gases are: 2  nitrogen (N2) - 78.084%. 3  oxygen (O2) - 20.9476%. 4  argon (Ar) - 0.934%. 5  carbon dioxide (CO2) 0.0314%.