In some types of atom, the nucleus is unstable , and will decay into a more stable atom. This radioactive decay is completely spontaneous . This form of Lithium is not radioactive - it's just an example of a simple atom. Most radioactive substances have many more particles in their nucleus. When an unstable nucleus decays, there are three ways that it can do so.
Many radioactive substances emit a particles and b particles as well as g rays.
Click the button. Alpha particles are made of 2 protons and 2 neutrons . Alpha particles are relatively slow and heavy . They have a low penetrating power - you can stop them with just a sheet of paper . Because they have a large charge, alpha particles ionise other atoms strongly.