Atoms (at least atoms larger than beryllium, give or take) are basically a classical particle for all intents and purposes. They have momentum (assuming non-zero temperature) and mass, and basically just keep flying in a direction until they hit something or a force acts on it to pull it in a new direction.

In a solid, the interactions with nearby atoms (through e.g. electrostatic interactions) and the degree to which the atoms are packed mean the ball's basically just vibrating in place.

In a molecule, "bonds" are just forces resulting from electrons being shared that makes it really tough to pull the atoms apart, but they are still basically just balls moving in a direction until they bounce into something, or a force pulls them in another direction.

There's some quantum weirdness about the nature of the forces themselves, but atoms generally behave F=ma just the same as macroscopic stuff.