At a boundary you can imagine gas atoms diffusing freely across the border in both directions.

While it is being accelerated it will collide with the gas atoms and be slowed down.

Strong stellar winds can also strip gas atoms from the top of an atmosphere causing them to be lost to space.

So we say that the microscopic position and momentum of the gas atoms do not have to be known in order to describe the gas.

In a plasma, gas atoms are excited to higher energy states and also ionized.

The gas atoms or molecules are adsorbed on the surfaces of the electrodes.

For example, given a box full of gas, many different arrangements of the gas atoms can have the same total energy.

When a muon passes through the chamber, electrons are knocked out of gas atoms.

Plasma is a collection of charged particles, such as free electrons or ionized gas atoms.

Without London forces, there would be no attractive force between noble gas atoms, and they wouldn't exist in liquid form.