When is the force between atoms attractive? When is it repulsive?

(N/A) The force between atoms depends on the distance $r$ between them relative to the equilibrium distance $r_0$ (where potential energy is minimum).
$1$. The force is repulsive when the distance between atoms is less than the equilibrium distance $(r < r_0)$. In this region,the electron clouds of the atoms overlap,leading to strong electrostatic repulsion.
$2$. The force is attractive when the distance between atoms is greater than the equilibrium distance $(r > r_0)$. In this region,the interatomic potential energy increases as $r$ increases,and the atoms experience an attractive force pulling them back toward the equilibrium position.