The atmosphere is full of wind, which keeps things pretty well mixed, at least in the troposphere.
In a hypothetical perfectly still atmosphere, the heavier molecules would tend to settle to the bottom. Even then, the air wouldn't be perfectly stratified like a layer cake, because there is enough thermal energy to mix the layers. But you would observe that, as the elevation increased, the concentration of heavier molecules dropped off faster than the concentration of lighter molecules.
eotfofylgg t1_jclfjlr wrote
Reply to comment by Alfred_The_Sartan in What makes one greenhouse gas stronger at trapping heat than another? by sand_eater
The atmosphere is full of wind, which keeps things pretty well mixed, at least in the troposphere.
In a hypothetical perfectly still atmosphere, the heavier molecules would tend to settle to the bottom. Even then, the air wouldn't be perfectly stratified like a layer cake, because there is enough thermal energy to mix the layers. But you would observe that, as the elevation increased, the concentration of heavier molecules dropped off faster than the concentration of lighter molecules.