In nuclear reactions, significant changes occur in the composition of the nuclei of the atoms involved. These reactions usually release tremendous amounts of energy. One of the reasons for the nuclear changes can be attributed to the stability of the nucleus.
The formation of nucleus from the subatomic particles - neutrons and protons, results in the release of energy. The mass of these individual particles in the nucleus is greater than that of the actual nucleus that is formed. This loss of mass is due to the change of mass into energy. The energy-mass relation can be represented in terms of the equation:
E = mc2,
where m represents the mass, and c represents the speed of light (3x108 m/s).
If the nucleus of an atom is not stable, it can get transformed into another nucleus. A plot of the number of neutrons versus the number of protons is often used to assess the stability trends of elements. If the number of protons and neutrons are equal, the nucleus is considered to be reasonably stable. As the atomic number increases, the trend changes.
Isotopes of elements having atomic numbers above »83 are unstable atoms. These unstable atoms can undergo disintegrations. The half-lives of some radioactive elements are shown in Table 1.
A sample of 226Ra disintegrates to 3% of its original quantity. How many half-lives have this sample passed?