The protons which repeal each other electrostatically & the neutron which exert no electric force are held extremely close together inside a stable nucleus. In this topic, we will learn the properties of nuclear forces.
Obviously, there are some forces operating within the nucleus which binds neutron to proton (n-p forces), proton to protons ( p-p forces) and neutron to neutron (n-n forces). These forces bind the nucleus.
Nuclear forces have the following properties :
i) They are attractive: The overall effect of Nuclear forces is attractive otherwise the nucleus will not exist.
ii) They are non-electric: The nuclear forces cannot be of an electrical nature. If it will so, the protons will repel one another.
iii) They are non-gravitational.
iv) They are extremely strong: The nuclear forces are the strongest known forces in nature. Therefore they provide stability to the nucleus.
v) They are extremely short range forces: These forces are applicable only in a small region of the order of 10^-15 m. These forces do not obey the inverse square law.
vi) They are spin dependent: Experimental pieces of evidence shows that the nuclear force acting between two nucleons depends upon the mutual orientation of spins of nucleons. e.g. a neutron and a proton are kept together forming a deuteron only if their spins are parallel to each other.