Question
If x is the number of electrons and y is the number of nucleons present in ^ 32 _ 16 S ^ 2- , then which one of the following is correct?
NDA
General Ability
General Science
2026
NDA 2026 (Phase 1)
NDA General Ability Question (2026) — Solution
Options
- A. x = 14 and y = 32
- B. x = 16 and y = 30
- C. x = 18 and y = 32
- D. x = 18 and y = 30
Answer
C. x = 18 and y = 32
Step-by-step solution
The given species is ^ 32 _ 16 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.
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