The structure of the neutron:
The neutron is one of the two constituent parts of an atomic nucleus. The neutron can be treated as a proton that has lost its electrical charge. It is also a very small particle whose radius is equivalent to one millionth of a billionth of a metre, composed of even smaller particles known as quarks. In its free state, the neutron is highly unstable but once inside the nucleus it regains stability. Its lack of electrical charge allows it to be captured easily by nuclei and, occasionally, can cause nuclear reactions.