Step-by-step explanation:
It is known that an atom consists of three subatomic particles which are protons, neutrons and electrons.
Protons and neutrons reside inside the nucleus whereas electrons revolve around the nucleus. Also, protons have positive charge, neutrons have no charge and electrons are negatively charged.
Due to same charge on each proton there occurs electrostatic repulsion in the nucleus of the atom but a force that overcomes this repulsion and helps in binding of protons and neutron together is known as strong nuclear force also known as nuclear binding energy.
Thus, we can conclude that protons and neutrons are held together by the strong nuclear force.