Which of the following is expected to be coloured in solutions

Options

A. `Cu^(+)`
B. `Cu^(2+)`
C. `Ti^(4+)`
D. `Sc^(3+)`

Answer

To determine which of the given species is expected to be colored in solution, we need to analyze the electronic configurations of each species and check for the presence of unpaired electrons. The presence of unpaired electrons allows for d-d transitions, which are responsible for the color observed in transition metal complexes.

### Step-by-Step Solution:

1. **Identify the Species**: The question involves several species from the d-block elements. We need to analyze each one.

2. **Write the Electronic Configuration**:
- **Copper (Cu)**: Atomic number = 29
- Ground state configuration: [Ar] 3d¹⁰ 4s¹
- For Cu²⁺: Remove one electron from 4s: [Ar] 3d¹⁰ 4s⁰
- Configuration for Cu²⁺: [Ar] 3d¹⁰
- **Unpaired Electrons**: 0 (All electrons are paired)

- **Copper (Cu²⁺)**:
- Configuration: [Ar] 3d⁹
- **Unpaired Electrons**: 1 (There is one unpaired electron)

- **Titanium (Ti)**: Atomic number = 22
- Ground state configuration: [Ar] 3d² 4s²
- For Ti⁴⁺: Remove four electrons (two from 4s and two from 3d): [Ar] 3d⁰ 4s⁰
- Configuration for Ti⁴⁺: [Ar]
- **Unpaired Electrons**: 0 (No electrons in d-orbital)

- **Scandium (Sc)**: Atomic number = 21
- Ground state configuration: [Ar] 3d¹ 4s²
- For Sc³⁺: Remove three electrons (two from 4s and one from 3d): [Ar] 3d⁰ 4s⁰
- Configuration for Sc³⁺: [Ar]
- **Unpaired Electrons**: 0 (No electrons in d-orbital)

3. **Determine Color Presence**:
- **Cu²⁺**: Has 1 unpaired electron → **Colored**
- **Cu**: Has 0 unpaired electrons → **Not Colored**
- **Ti⁴⁺**: Has 0 unpaired electrons → **Not Colored**
- **Sc³⁺**: Has 0 unpaired electrons → **Not Colored**

4. **Conclusion**: The only species that is expected to be colored in solution is **Cu²⁺** due to the presence of one unpaired electron, which allows for d-d transitions.

### Final Answer:
**Cu²⁺ is expected to be colored in solution.**

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