Question

A certain nucleus A (mass number 238 and atomic number 92) is radioactive and becomes a nucleus B (mass number 234 and atomic number 90) by the emission of a particle.

1. Name the particle emitted.
2. Explain how you arrived at your answer.
3. State the change in the form of a reaction.

Answer 1

\[\ce{^238_92A -> ^234_90B}\]

1. α - particle
2. ∵ Mass Number has decreased by 4 and atomic number has decreased by 2.
3. This change can be expressed in the form of a reaction as follows:
   \[\ce{\underset{Parent nucleus}{_92^238A} -> \underset{Daughter nucleus}{_90^234B} + \underset{(\alpha-particle)}{_2^4He}}\]