Which of the following has largest paramagnetism ?

Options

A. `[Cr(H_(2)O)_(6)]^(3+)`
B. `[Fe(H_(2)O)_(6)]^(2+)`
C. `[Cu(H_(2)O)_(6)]^(2+)`
D. `[Zn(H_(2)O)_(2)]^(2+)`

Explanation

To determine which of the given compounds has the largest paramagnetism, we need to analyze the electronic configurations of the metal ions in their respective oxidation states and count the number of unpaired electrons. Here's a step-by-step breakdown of the solution:

### Step 1: Understand Paramagnetism
Paramagnetism arises from the presence of unpaired electrons in an atom or ion. The more unpaired electrons present, the stronger the paramagnetic behavior.

**Hint:** Remember that only unpaired electrons contribute to paramagnetism.

### Step 2: Identify the Metal Ions and Their Oxidation States
The question involves several metal ions:
- Chromium (Cr) in +3 oxidation state
- Iron (Fe) in +2 oxidation state
- Copper (Cu) in +2 oxidation state
- Zinc (Zn) in +2 oxidation state

**Hint:** Write down the oxidation states of the metals to keep track of their electron loss.

### Step 3: Determine the Electronic Configurations
1. **Chromium (Cr)**: Atomic number = 24
- Electronic configuration: [Ar] 3d^5 4s^1
- In +3 state: Loses 3 electrons → [Ar] 3d^3

2. **Iron (Fe)**: Atomic number = 26
- Electronic configuration: [Ar] 3d^6 4s^2
- In +2 state: Loses 2 electrons → [Ar] 3d^6

3. **Copper (Cu)**: Atomic number = 29
- Electronic configuration: [Ar] 3d^10 4s^1
- In +2 state: Loses 2 electrons → [Ar] 3d^9

4. **Zinc (Zn)**: Atomic number = 30
- Electronic configuration: [Ar] 3d^10 4s^2
- In +2 state: Loses 2 electrons → [Ar] 3d^10

**Hint:** Write down the electronic configurations for clarity.

### Step 4: Count the Unpaired Electrons
- **Cr^3+ (3d^3)**: 3 unpaired electrons
- **Fe^2+ (3d^6)**: 4 unpaired electrons
- **Cu^2+ (3d^9)**: 1 unpaired electron
- **Zn^2+ (3d^10)**: 0 unpaired electrons

**Hint:** Remember that in weak field ligands like water, electrons will not pair up.

### Step 5: Compare the Number of Unpaired Electrons
- Cr^3+: 3 unpaired electrons
- Fe^2+: 4 unpaired electrons (highest)
- Cu^2+: 1 unpaired electron
- Zn^2+: 0 unpaired electrons

**Hint:** The metal ion with the highest number of unpaired electrons will exhibit the largest paramagnetism.

### Step 6: Conclusion
The metal ion with the largest number of unpaired electrons is **Fe^2+**, which has 4 unpaired electrons. Therefore, it shows the largest paramagnetism among the given options.

**Final Answer:** The compound with the largest paramagnetism is the one containing **Fe^2+**.