Q76 / 270 · NDA 2026 (Phase 1) · General Ability
If $x$ is the number of electrons and $y$ is the number of nucleons present in ${}^{32}_{16}\text{S}^{2-}$, then which one of the following is correct?
- A$x = 14$ and $y = 32$
- B$x = 16$ and $y = 30$
- Correct answerC$x = 18$ and $y = 32$
- D$x = 18$ and $y = 30$
Solution
The given species is ${}^{32}_{16}\text{S}^{2-}$.
The atomic number $Z$ of sulfur is $16$, which represents the number of protons.
Since the species has a charge of $-2$, it has gained $2$ electrons. Therefore, the number of electrons $x = 16 + 2 = 18$.
The mass number $A$ is $32$. The number of nucleons is the sum of protons and neutrons, which is equal to the mass number. Therefore, the number of nucleons $y = 32$.
Thus, $x = 18$ and $y = 32$.
The atomic number $Z$ of sulfur is $16$, which represents the number of protons.
Since the species has a charge of $-2$, it has gained $2$ electrons. Therefore, the number of electrons $x = 16 + 2 = 18$.
The mass number $A$ is $32$. The number of nucleons is the sum of protons and neutrons, which is equal to the mass number. Therefore, the number of nucleons $y = 32$.
Thus, $x = 18$ and $y = 32$.
Hence, the correct answer is option: 'C'.