Question

An atomic nucleus A is composed of $84$ protons and $128$ neutrons. The nucleus A emits $\alpha$-particle and is transformed into a nucleus B. What is the composition of B ?

• A. $84$ protons and $126$ neutrons
• B. $86$ protons and $126$ neutrons
• C. $82$ protons and $126$ neutrons
• D. $82$ protons and $128$ neutrons

Answer 1

The correct option is C $82$ protons and $126$ neutrons

Emission on alpha particle will reduce neutron by $2$ and proton by $2$.

So, in final we have proton $=84-2=82$, neutron $=128-2=126$