The
nuclear force (or
nucleon–nucleon interaction or
residual strong force) is the force between
protons and
neutrons,
subatomic particles that are collectively called
nucleons. The nuclear force is responsible for binding
protons and
neutrons into
atomic nuclei. Neutrons and protons are affected by the nuclear force almost identically. Since protons have charge +1
e, they experience a strong electric field repulsion (following
Coulomb's law) that tends to push them apart, but at short range the attractive nuclear force overcomes the repulsive electromagnetic force. The mass of a
nucleus is less than the sum total of the individual masses of the protons and neutrons which form it. The difference in mass between bound and unbound nucleons is known as the
mass defect.
Energy is released when some large nuclei break apart, and it is this energy that is used in
nuclear power and
nuclear weapons.