What is the order of the substances in the air from least abundant to most abundant?

To determine the correct order of the substances in the air from least abundant to most abundant, it's important to understand the composition of Earth's atmosphere.

The major constituents of dry air are nitrogen (N2), which makes up about 78% of the atmosphere, and oxygen (O2), which accounts for about 21%. Argon (Ar) is present in much smaller amounts, roughly 0.93%. Carbon dioxide (CO2) is even less abundant, currently around 0.04% and is increasing due to human activities. Ozone (O3) is found in trace amounts, typically around 0.000006% in the atmosphere.

Arranging these gases from least abundant to most abundant, we get:

1. Ozone (O3) - extremely low concentration

2. Carbon dioxide (CO2) - low concentration, but higher than O3

3. Argon (Ar) - more abundant than CO2

4. Oxygen (O2) - the second most abundant gas

5. Nitrogen (N2) - the most abundant gas in the atmosphere

The correct order of these substances from least to most abundant is indeed O3, CO2, Ar, O2, N2. This