An atom has various particles in it and these are called sub atomic particles and include electrons, protons, neutrons etc. Neutrons are also a form of particles within an atom and they do not have any kind of charge on them. They were discovered in 1930 and they have been shown to exhibit both wave and particle nature. They have very high penetrating powers. A neutron is made up of three quarks, two down and one up. When they decay they become a proton. They play a very important role in radioactive reactions but exposure to neutrons can be very harmful.