Which of the following sets contain only isoelectronic ions?

Options

A. `Zn^(+), Ca^(2+), Ga^(2+), Al^(3+)`
B. `K^(+), Ca^(2+), Sc^(3+), Cl^(-)`
C. `P^(3-), S^(2-), Cl^(-), K^(+)`
D. `Ti^(4+), Ar, Cr^(3-), V^(5+)`

Explanation

To determine which sets contain only isoelectronic ions, we need to identify the number of electrons in each ion and see if they are the same across the ions in each set. Isoelectronic ions are ions that have the same number of electrons.

### Step-by-Step Solution:

1. **Understanding Isoelectronic Ions**:
- Isoelectronic ions have the same number of electrons. For example, if two ions both have 18 electrons, they are isoelectronic.

2. **Analyzing Each Option**:
- We will evaluate each option given in the question to check for isoelectronic ions.

3. **Option 1: Zn²⁺, Ca²⁺, Ga²⁺, Al³⁺**:
- **Zn²⁺**: Atomic number of Zn = 30. It loses 2 electrons: 30 - 2 = 28 electrons.
- **Ca²⁺**: Atomic number of Ca = 20. It loses 2 electrons: 20 - 2 = 18 electrons.
- **Ga²⁺**: Atomic number of Ga = 31. It loses 2 electrons: 31 - 2 = 29 electrons.
- **Al³⁺**: Atomic number of Al = 13. It loses 3 electrons: 13 - 3 = 10 electrons.
- **Conclusion**: This set does not contain isoelectronic ions.

4. **Option 2: K⁺, Ca²⁺, Sc³⁺, Cl⁻**:
- **K⁺**: Atomic number of K = 19. It loses 1 electron: 19 - 1 = 18 electrons.
- **Ca²⁺**: Atomic number of Ca = 20. It loses 2 electrons: 20 - 2 = 18 electrons.
- **Sc³⁺**: Atomic number of Sc = 21. It loses 3 electrons: 21 - 3 = 18 electrons.
- **Cl⁻**: Atomic number of Cl = 17. It gains 1 electron: 17 + 1 = 18 electrons.
- **Conclusion**: All ions in this set have 18 electrons, so this set contains isoelectronic ions.

5. **Option 3: P³⁻, S²⁻, Cl⁻, K⁺**:
- **P³⁻**: Atomic number of P = 15. It gains 3 electrons: 15 + 3 = 18 electrons.
- **S²⁻**: Atomic number of S = 16. It gains 2 electrons: 16 + 2 = 18 electrons.
- **Cl⁻**: Atomic number of Cl = 17. It gains 1 electron: 17 + 1 = 18 electrons.
- **K⁺**: Atomic number of K = 19. It loses 1 electron: 19 - 1 = 18 electrons.
- **Conclusion**: All ions in this set have 18 electrons, so this set also contains isoelectronic ions.

6. **Option 4: Ti⁴⁺, Ar, Cr³⁺**:
- **Ti⁴⁺**: Atomic number of Ti = 22. It loses 4 electrons: 22 - 4 = 18 electrons.
- **Ar**: Atomic number of Ar = 18. It has 18 electrons.
- **Cr³⁺**: Atomic number of Cr = 24. It loses 3 electrons: 24 - 3 = 21 electrons.
- **Conclusion**: This set does not contain isoelectronic ions (Ti⁴⁺ and Ar have 18 electrons, but Cr³⁺ has 21).

### Final Conclusion:
- The sets that contain only isoelectronic ions are **Option 2** and **Option 3**.