<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> The nuclear force (or nucleon--nucleon interaction or residual strong force) is a force that acts between the protons and neutrons of atoms . Neutrons and protons, both nucleons, are affected by the nuclear force almost identically . Since protons have charge + 1 e, they experience an electric force that tends to push them apart, but at short range the attractive nuclear force is strong enough to overcome the electromagnetic force . The nuclear force binds nucleons into atomic nuclei . </P> <P> The nuclear force is powerfully attractive between nucleons at distances of about 1 femtometre (fm, or 1.0 × 10 metres), but it rapidly decreases to insignificance at distances beyond about 2.5 fm . At distances less than 0.7 fm, the nuclear force becomes repulsive . This repulsive component is responsible for the physical size of nuclei, since the nucleons can come no closer than the force allows . By comparison, the size of an atom, measured in angstroms (Å, or 1.0 × 10 m), is five orders of magnitude larger . The nuclear force is not simple, however, since it depends on the nucleon spins, has a tensor component, and may depend on the relative momentum of the nucleons . The nuclear force is not one of the fundamental forces of nature . </P>

The force that holds neutrons and protons together in the nucleus is known as