Which group contains coloured ions out of the following ?
1. `Cu^+` 2. `Ti^(4+)` 3. `Co^(2+)` 4. `Fe^(2+)`

Options

A. a. 1,2,3,4
B. b. 3,4
C. c. 2,3
D. d. 1,2

Explanation

To determine which of the given ions are colored, we need to analyze their electronic configurations and check for the presence of unpaired electrons in the d-orbitals. The presence of unpaired electrons is what typically results in colored ions.

### Step-by-Step Solution:

1. **Analyze Cu⁺ (Copper Ion)**:
- Atomic number of Cu (Copper) = 29.
- Electronic configuration of Cu: \( [Ar] 4s^2 3d^{9} \).
- When Cu loses one electron to form Cu⁺, it loses one from the 4s orbital:
- Configuration of Cu⁺: \( [Ar] 3d^{10} \).
- In \( 3d^{10} \), all electrons are paired.
- **Conclusion**: Cu⁺ is colorless.

2. **Analyze Ti⁴⁺ (Titanium Ion)**:
- Atomic number of Ti (Titanium) = 22.
- Electronic configuration of Ti: \( [Ar] 4s^2 3d^{2} \).
- When Ti loses four electrons to form Ti⁴⁺, it loses both from the 4s and 3d orbitals:
- Configuration of Ti⁴⁺: \( [Ar] \) (no d electrons).
- **Conclusion**: Ti⁴⁺ is colorless.

3. **Analyze Co²⁺ (Cobalt Ion)**:
- Atomic number of Co (Cobalt) = 27.
- Electronic configuration of Co: \( [Ar] 4s^2 3d^{7} \).
- When Co loses two electrons to form Co²⁺, it loses both from the 4s orbital:
- Configuration of Co²⁺: \( [Ar] 3d^{7} \).
- In \( 3d^{7} \), there are unpaired electrons:
- The filling of \( 3d \) orbitals gives us \( 3d^{7} \) with 3 unpaired electrons.
- **Conclusion**: Co²⁺ is colored.

4. **Analyze Fe²⁺ (Iron Ion)**:
- Atomic number of Fe (Iron) = 26.
- Electronic configuration of Fe: \( [Ar] 4s^2 3d^{6} \).
- When Fe loses two electrons to form Fe²⁺, it loses both from the 4s orbital:
- Configuration of Fe²⁺: \( [Ar] 3d^{6} \).
- In \( 3d^{6} \), there are unpaired electrons:
- The filling of \( 3d \) orbitals gives us \( 3d^{6} \) with 4 unpaired electrons.
- **Conclusion**: Fe²⁺ is colored.

### Final Conclusion:
- The colored ions from the given options are Co²⁺ and Fe²⁺.
- Therefore, the correct answer is **Co²⁺ and Fe²⁺**.

### Summary of Results:
- **Cu⁺**: Colorless
- **Ti⁴⁺**: Colorless
- **Co²⁺**: Colored
- **Fe²⁺**: Colored