Question

Composition of nuclei of two atomic species $X$ and $Y$ are given as under:
$$\begin{array}{ccc}& X& Y\\ \text{Protons}=& 6& 6\\ \text{Neutrons}=& 6& 8\end{array}$$
Choose the correct answers, among the following?

• A. Mass number of $X$ is $12$ and $Y$ is $14$ and $X$ and $Y$ are isotopes of each other
• B. Mass number of $X$ is $14$ and $Y$ is $12$ and $X$ and $Y$ are isobars of each other
• C. Mass number of $X$ is $12$ and $Y$ is $14$ and $X$ and $Y$ are isobars of each other
• D. Mass number of $X$ is $14$ and $Y$ is $12$ and $X$ and $Y$ are isotopes of each other

Answer 1

The correct option is A Mass number of $X$ is $12$ and $Y$ is $14$ and $X$ and $Y$ are isotopes of each other

The composition of the nuclei of two atomic species $X$ and $Y$ are given as under Protons = $6\left(X\right):6\left(Y\right)$ Neutrons = $6\left(X\right):8\left(Y\right)$

Mass number of $X$ = Number of protons + Number of neutrons = $6+6=12$.
Mass number of $Y$ = Number of protons + Number of neutrons = $6+8=14$.

These two atomic species, $X$ and $Y$, have the same atomic number but different mass numbers. Hence, they are isotopes.