Question

A certain nucleus A (mass number 238 and atomic number 92) is radioactive and becomes a nucleus (mass number 234 and atomic number 90) by the loss of a particle. (a) What particle was emitted ?

• A. alpha
• B. beta
• C. gamma
• D. all the above

Answer 1

The correct option is A alpha

Emission of alpha particle reduces the proton by $2$ and neutron by $2$, so mass number is reduced by 4 and atomic number by $2$.

New mass number is: $238-4=234$, and atomic number is: $92-2=90$