Question

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

1. Name the particle emitted. Give reason.
2. State the change in the form of a nuclear reaction.

Answer 1

i. The mass number decreases from 238 to 234:

238 − 234 = 4

The atomic number decreases from 92 to 90:

92 − 90 = 2

A particle having mass number 4 and atomic number 2 is an α-particle \[\ce{(^4_2He)}\].

ii. \[\ce{^238_92B -> ^234_90A + ^4_2He}\]

Thus, the emitted particle is an alpha particle.