There is an important equilibrium in the atom that we must consider: the balance between its nucleus and electrons.
Put in its simplest terms, electrons revolve around the nucleus. The reason for this is electrical charge. Electrons have a negative charge and protons have a positive charge. Opposite charges attract, so an atom’s electrons are drawn towards the nucleus. But the electrons are also moving at an enormous speed which would, under normal conditions, cause them to shoot away from the nucleus. These two forces (attraction and motion away) are balanced so that the electrons move in orbits around the nucleus.