Question

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

• A. $80$ protons and $126$ neutrons
• B. $82$ protons and $126$ neutrons
• C. $82$ protons and $124$ neutrons
• D. $80$ protons and $124$ neutrons

Answer 1

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

Number of protons left in nucleus of B is $84-2=82$.

Number of neutrons left in nucleus of B is $128-2=126$.