Since lighter molecules are moving faster, they escape from an atmosphere more often than more massive ones.
The escape velocity is the velocity that an object must be given in order to escape from the gravitational field of the earth. We must know that a less massive molecule moves faster than a more massive molecule.
Hence, less massive molecules tend to escape from an atmosphere more often than more massive ones because they are moving faster.
Learn more about escape velocity: https://brainly.com/question/26934080