Among the following, the set of isoelectronic ions is

Options

A. `Na^(+) , Mg^(2+) , F^(-) , Cl^(-)`
B. `Na^(+) , Ca^(2+) , F^(-) O^(2-)`
C. `Na^(+) , Mg^(2+) , F^(-) , O^(2-)`
D. `Na^(+) , K^(+) , S^(2-) , Cl^(-)`

Explanation

To determine the set of isoelectronic ions among the given options, we need to find ions that have the same number of electrons. Let's analyze each option step by step.

### Step 1: Understand Isoelectronic Species
Isoelectronic species are ions or atoms that have the same number of electrons.

### Step 2: Identify the Atomic Numbers and Calculate Electrons
We will calculate the number of electrons for each ion in the options provided.

#### Option A: Na+, Mg2+, F-, Cl-
- **Na+**: Sodium (Na) has an atomic number of 11. When it loses one electron to become Na+, it has 10 electrons.
- **Mg2+**: Magnesium (Mg) has an atomic number of 12. When it loses two electrons to become Mg2+, it has 10 electrons.
- **F-**: Fluorine (F) has an atomic number of 9. When it gains one electron to become F-, it has 10 electrons.
- **Cl-**: Chlorine (Cl) has an atomic number of 17. When it gains one electron to become Cl-, it has 18 electrons.

**Conclusion for A**: Na+, Mg2+, and F- have 10 electrons, but Cl- has 18 electrons. Therefore, this option is not a set of isoelectronic ions.

#### Option B: Na+, Ca2+, F-, O2-
- **Na+**: 10 electrons (as calculated above).
- **Ca2+**: Calcium (Ca) has an atomic number of 20. When it loses two electrons to become Ca2+, it has 18 electrons.
- **F-**: 10 electrons (as calculated above).
- **O2-**: Oxygen (O) has an atomic number of 8. When it gains two electrons to become O2-, it has 10 electrons.

**Conclusion for B**: Na+, F-, and O2- have 10 electrons, but Ca2+ has 18 electrons. Therefore, this option is not a set of isoelectronic ions.

#### Option C: Na+, Mg2+, F-, O2-
- **Na+**: 10 electrons (as calculated above).
- **Mg2+**: 10 electrons (as calculated above).
- **F-**: 10 electrons (as calculated above).
- **O2-**: 10 electrons (as calculated above).

**Conclusion for C**: All species (Na+, Mg2+, F-, O2-) have 10 electrons. Therefore, this option is a set of isoelectronic ions.

#### Option D: Na+, K+, S2-, Cl-
- **Na+**: 10 electrons (as calculated above).
- **K+**: Potassium (K) has an atomic number of 19. When it loses one electron to become K+, it has 18 electrons.
- **S2-**: Sulfur (S) has an atomic number of 16. When it gains two electrons to become S2-, it has 18 electrons.
- **Cl-**: 18 electrons (as calculated above).

**Conclusion for D**: Na+ has 10 electrons, while K+, S2-, and Cl- have 18 electrons. Therefore, this option is not a set of isoelectronic ions.

### Final Answer
The only correct option that represents a set of isoelectronic ions is **C: Na+, Mg2+, F-, O2-**.