In the quantum mechanical model of the atom, the nucleus, which contains protons and neutrons, is located at the center. The protons carry positive electric charge, and therefore, there is a repulsive electrostatic force between them. One might wonder why the protons do not repel each other and fly apart, causing the nucleus to disintegrate.
The stability of the nucleus is due to the strong nuclear force, also known as the strong interaction or strong force. The strong force is one of the fundamental forces of nature and is responsible for holding the nucleus together. It is a very powerful force, much stronger than the electromagnetic force responsible for the repulsion between protons.
The strong force acts between quarks, which are the fundamental particles that make up protons and neutrons. It binds the quarks together to form protons and neutrons and also holds the protons and neutrons together within the nucleus. The strong force has a very short range, acting only over distances comparable to the size of an atomic nucleus.
So, while the protons in the nucleus do repel each other due to their positive charge, the strong force is strong enough to overcome this repulsion and hold the nucleus together. The balance between the repulsive electromagnetic force and the attractive strong force determines the stability of the nucleus and its ability to remain at the center of the atom.