Question

A nucleus emits one $\alpha$-particle and forms a new nucleus. The mass and charge of the new nucleus is changed in one of the following way

• A. mass is reduced by 2 and charge is reduced by 2
• B. mass is reduced by 4 and charge is reduced by 6
• C. mass is reduced by 2 and charge is reduced by 4
• D. mass is reduced by 4 and atomic no. is reduced by 2.

Answer 1

Answer: (D)

When one $\alpha$ -particle is emitted, the mass $(A)$ is reduced by $4$ and atomic no. $(Z)$ is teduced by $2$.
Therefore for new nucleus, mass no. is $(A-4)$ and atomic no. is $(Z-2)$