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
The most probable set of particles that were given off during the series of nuclear changes from 232Th to 224Ra are:
|A||Two alpha particles and one beta particle|
|B||One alpha particle and two beta particle|
|C||One alpha particle and three beta particles|
|D||Two alpha particles and two beta particles|
The question tests your ability to evaluate radioactive emissions by analyzing a given radioactive emission reaction. Notice that the atomic number decreased by 2 and the mass number decreased by 8. If two alpha particles were emitted, that would decrease the mass number to 224, because an alpha particle is a helium nucleus
It would also decrease the atomic number by 4. But apparently that is not the case here. The atomic number decrease by only 2. This can be accounted for if two β-particles were also emitted.