Question

Explain with example α - decay.

Answer 1

1. The emission of α - particles from the nuclei of a radioelement is called α - decay.
2. The charge on an α-particle is +2 with a mass of 4 u.
   It is identical to the helium nucleus and hence an α-particle is designated as \[\ce{^4_2He}\].
3. In the α-decay process, the parent nucleus \[\ce{^A_ZX}\] emits an α-particle and produces daughter nucleus Y. The parent nucleus thus loses two protons (charge +2) and two neutrons. The total mass lost is 4 u. The daughter nucleus will, therefore, have mass 4 units less and charge 2 units less than its parent.
4. General equation for α-decay process can be given as:
   \[\ce{\underset{\text{Parent}}{^A_ZX} -> \underset{\text{Daughter nuclei}}{^{A - 4}_{Z - 2}X} + \underset{\text{Emitted particle}}{^4_2He}}\]
   e.g. Radium 226 decays to form radium 222:
   \[\ce{\underset{\text{Parent}}{^226_88Ra} ->\underset{\text{Daughter nuclei}}{^222_86Rn} + \underset{\text{Emitted particle}}{^4_2He}}\]
   In α-decay process of radium, radon (daughter nuclei) is formed with loses of two protons (charge +2) and two neutrons. The total mass lost is 4 u.
   Thus, radon has a mass of 4 units less and charge 2 units less than its parent radium.