Atoms with unstable nuclei decompose into atoms with stable nuclei. This process of decomposition is known as Radioactivity. The particles released during radioactivity are associated with energy which s called radioactive energy. The decaying rate of these atoms is constant over time. During the decay in radioactivity, an atom with a nucleus transforms into another atom with a different nucleus. This transformation results in emission of energy called radiation. When radioactivity occurs naturally then it is called natural radioactivity. If the radioactivity is developed in laboratory conditions then it is referred to as induced radioactivity.
Radioactivity was discovered by Henry Becquerel in 1896. The rays emitted during radioactivity decomposition are known as alpha rays, beta rays and gamma rays. Alpha decay in radioactivity occurs in higher elements only and the other two decays occur almost in all elements.
Alpha rays carry a positive charge. Alpha rays are more massive than the beta rays. The alpha rays consists of helium nucleus. The atomic mass of helium is 4 and charge is +2. Hence ejection of an alpha particle from a nucleus results in the lowering of its atomic mass and atomic number.
Research proved that the beta rays and cathode rays are similar. Hence we came to know that both these rays are a stream of electrons. When a beta particle or an electron is emitted from a nucleus, a neutron is converted in to a proton. Hence the atomic mass of the nucleus remains the same and the atomic number increases by one unit.
The gamma rays in radioactivity and X-rays in electromagnetic radiation are same. They both are high energy radiation. Gamma rays cause no change in the atomic number or atomic mass of an atom. Gamma rays are emitted when there is energy change in the nucleus of atom itself. Usually gamma radiation accompanies the alpha and beta radiation.
The alpha, beta and gamma rays occur in nature and also in induced radioactivity. Radioactivity can be produced in a lab by bombarding a stable nucleus in to unstable or radioactive one. In induced radioactivity, heavy elements can be produced including those does not occur in nature.
Positron has same mass like an electron but with positive charge instead of negative. Positron can be produced only in induced radioactivity.
Hence radioactivity can be used both for constructive and destructive purpose. However precautions are needed while using radioactivity for beneficial use