Inter Atomic Force in Gases
Interatomic distance in gases is very large and interatomic force is very small compared to solids and liquids. So, in gaseous state molecules remain in a random state. Then molecules with more vibration, rotation and translation overcoming the interatomic forces move freely. Molecules isolate from one other. So, gases do not have fixed shape and volume. Since molecules do not stay nearer, so volume of gaseous material becomes much more than that of solids and liquids. In this state there exists maximum vibration, rotation and motion among the atoms of material. As there exists large vacant spaces between molecules, volume reduces significantly when pressure is applied.
On the other hand, if the value of kinetic energy is more than interatomic attractive force then the material attains gaseous state. In this situation gas molecules can move freely from one place to another place. When distance between gas molecules decreases and due to the repulsion different positive nuclei repulsive force is generated, then potential energy of the system increases.
Inter-atomic force depends on inter-atomic distance. If two molecules are very close, repulsive force acts between them. If the distance of two atoms is slightly more, attraction force acts. Inter-atomic distance has a definite value for which attractive a repulsive forces become same i.e., at that distance resultant force between the molecules is zero.