The principal factor for determining whether a nucleus is stable is the neutron to proton ratio. Elements with (Z<20) are lighter and these elements' nuclei and have a ratio of 1:1 and prefer to have the same amount of protons and neutrons.
Facts about neutron:
James Chadwick discovered the neutron in 1932. He discovered it using this curious device which he made from pieces found in the laboratory.
Neutrons are very small indeed.
There are stars made of neutrons.
Neutrons are slightly heavier than protons.
Neutrons are made of three quarks.
What charge is a neutron?: Neutrons have no charge. Since opposite charges attract, protons and electrons attract each