Radioactivity is spontaneous change of the nuclei of radioactive atoms, which in turn emits radiation. Radioactivity is the property exhibited by the radioactive isotopes of stable elements and all isotopes of radioactive elements, and can be either natural or artificial (man made). All isotopes of atomic weight 210 and greater are radioactive. Alpha, beta, and gamma radiation are ionizing in their effect and are therefore dangerous to body tissues, especially if a radioactive substanceis ingested or inhaled.
Natural Radioactivity is energy generated by those radioactive elements that exist in the Earth's crust. Radioactivity in nature comes from two main sources, terrestrial and cosmic. Terrestrial radioisotopes are found on the earth that came into existence with the creation of the planet. Although some are long gone, some radioisotopes take a long time to decay and become non-radioactive (on the order of hundreds of millions of years) and are still around today. Radioactive elements found in rock, soil, water, air, and in food from the earth make there way in our bodies when we drink water, breath air or eat foods, which contain them. These naturally occurring radioisotopes such as carbon-14, potassium-40, thorium-223, uranium-238, polonium-218, and tritium (hydrogen-3) expose us to radiation from within our bodies. When elements decay, they decay at different rates and over longer periods of time. .
These are the different types of decay that occur: Alpha Decay, Beta Decay and Gamma Radiation.
Alpha particles are positively charged, high-energy particle emitted from the nucleus of a radioactive atom. It is one of the products of the spontaneous disintegration of radioactive elements such as radium and thorium, and is identical with the nucleus of a helium atom that is, it consists of two protons and two neutrons. The process of emission, alpha decay, transforms one element into another, decreasing the atomic (or proton) number by two and the atomic mass (or nucleon number) by four.