Why do different gases have different densities?

[Qaawar]

I've read that gas molecules do not have any attractions or regulations between them...
So why do different gases have different densities?

 

[Borek]

Are their masses identical?

 

[Alcathous]

Density is mass over volume. So for a gas to have different densities, either the volume or the mass (or both) have to be different. This also means that either the volume or the mass can be the same.

The claim you mention in your post, does that reflect on the mass part of the volume part?

 

[Borek]

Do you know what ideal gas is? And how its volume is related to the number of moles?

For a given number of moles and given p, T conditions, does the volume of the gas (as long as it is well described by the ideal gas approximation) depend on the gas identity?