Nuclear Chemistry and RadioactivityhardMCQ SINGLE⭐ Must-Do

A highly unstable parent nucleus undergoes two successive emissions to directly form the completely Nuclear Chemistry and Radioactivity Chemistry Question

Question

A highly unstable parent nucleus undergoes two successive $\beta^-$ emissions to directly form the completely stable isotope ${}_{7}^{14}N$. What was the original number of neutrons present in the initial parent nucleus?

Answer: C

💡 Solution & Explanation

The reaction path is Parent $\rightarrow 2\beta^- + {}_{7}^{14}N$. Each $\beta^-$ emission increases $Z$ by 1 while keeping mass number $A$ constant. Reversing the reaction drops $Z$ by 2. Thus, parent $Z = 7 - 2 = 5$ and $A = 14$. The parent is ${}_{5}^{14}X$. Neutrons = $A - Z = 14 - 5 = 9$.

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