Course description

Half-life of a radioactive element: According to the radioactive decay law, N=〖N_0  e〗^(-λt) , an infinite time is required for the radioactivity to disappear completely. All radioactive elements are same in this respect. Hence, in order to compare one radioactive element with another, a term half-life is often used. The half-life of a radioactive element is defined as the time that it takes for one half of the atoms of that substance to disintegrate into another nuclear form (Fig. 5 a, b). These can range from mere fractions of a second, to many billions of years. Moreover, the half-life of a particular radionuclide is unique to that radionuclide. For example, the half-life of radium is 1620 years. This means that it takes 1620 years for one-half of a given quantity of radium to change into its daughter product radon. In another 1620 years, ½ of the remainder would have disintegrated leaving ¼ of the original amount behind (Fig. 5 c). 

In radioactive disintegration, the original atoms transform to new atoms of new element. These new atoms are also radioactive leading to a long chain of different radioactive atoms in the form of a series (Fig. 6). The transformations go on until an inactive, i.e., stable substance is reached. In a radioactive series, any two adjacent elements may be considered as parent and daughter, the former being that which by its own decay produces the later. 

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