Radioactivity, also called "Radioactive Decay" is the spontaneous break-down of certain nuclei. When this happens, elements transmute into other elements through decaying and giving off certain radioactive particles. Atoms that have the spontaneous ability to do this are called "Radioactive" There are three different types of radioactive decay: alpha, beta and gamma radiation.
Alpha Decay Edit
Alpha decay is the process of ejecting a alpha particle (two neutrons and two protons, equal to a Helium-4 nucleus) from the nucleus. When an atom ejects an alpha particle, it looses two neutrons and protons, resulting in a completely different element. When elements change, electrons are also lost, producing ions. Alpha decay is more common during the decay of heavier elements, such as Uranium and Plutonium. Because alpha particles cannot penetrate anything thicker than a sheet of paper, they are not harmful to the human skin.
Beta Decay Edit
There are two kinds of Beta Decay: Beta Plus and Beta Minus.
During Beta Plus Decay, a positron is given off, and a proton changes into a neutron, creating a different isotope of the element in question.