Which of the following have high value of reduction potential (`E_(M^(2+)|M)^@)`

Options

A. Cu
B. Cr
C. Zn
D. Fe

Answer

To determine which of the elements in the 3D series has a high value of reduction potential (E(M²⁺|M)⁰), we will analyze the electronic configurations of the elements and their oxidation states.

### Step 1: Identify the elements in the 3D series
The 3D series elements include:
- Scandium (Sc)
- Titanium (Ti)
- Vanadium (V)
- Chromium (Cr)
- Manganese (Mn)
- Iron (Fe)
- Cobalt (Co)
- Nickel (Ni)
- Copper (Cu)
- Zinc (Zn)

However, we will focus on the relevant elements that are commonly discussed in terms of their reduction potentials: Copper (Cu), Chromium (Cr), Zinc (Zn), and Iron (Fe).

### Step 2: Determine the ground state electronic configurations
- **Copper (Cu)**: [Ar] 3d¹⁰ 4s¹
- **Chromium (Cr)**: [Ar] 3d⁵ 4s¹
- **Zinc (Zn)**: [Ar] 3d¹⁰ 4s²
- **Iron (Fe)**: [Ar] 3d⁶ 4s²

### Step 3: Determine the electronic configurations in the +2 oxidation state
- **Cu²⁺**: 3d⁹ (loses 1 electron from 4s and 1 from 3d)
- **Cr²⁺**: 3d⁴ (loses 1 electron from 4s and 1 from 3d)
- **Zn²⁺**: 3d¹⁰ (loses 2 electrons from 4s)
- **Fe²⁺**: 3d⁶ (loses 2 electrons from 4s)

### Step 4: Analyze the stability of the configurations when reduced to the elemental state
- **Cu²⁺ to Cu**: 3d⁹ to 3d¹⁰ 4s¹ (fully filled d-subshell is stable)
- **Cr²⁺ to Cr**: 3d⁴ to 3d⁵ 4s¹ (half-filled d-subshell is stable but less stable than fully filled)
- **Zn²⁺ to Zn**: 3d¹⁰ to 3d¹⁰ 4s² (already stable, no change)
- **Fe²⁺ to Fe**: 3d⁶ to 3d⁷ 4s² (moving to a less stable configuration)

### Step 5: Determine the reduction potentials
The reduction potential is influenced by the stability of the resulting configuration:
- **Cu²⁺ to Cu** has a high positive reduction potential because it goes to a fully filled d-subshell (3d¹⁰).
- **Cr²⁺ to Cr** has a positive reduction potential but is less than that of Cu because it goes to a half-filled state (3d⁵).
- **Zn²⁺ to Zn** has a stable configuration but does not have a high positive potential as it remains in a fully filled state.
- **Fe²⁺ to Fe** has a lower reduction potential as it moves to a less stable configuration.

### Conclusion
The element with the highest value of reduction potential (E(M²⁺|M)⁰) among the given options is **Copper (Cu)**.