Increasing order of paramagnetism is

Options

A. `Cu^(2+) , Co^(2+) , Mn^(2+) , Ni^(2+)`
B. `Co^(2+) , Cu^(2+) , Mn^(2+) , Ni^(2+)`
C. `Cu^(2+) , Ni^(2+) , Co^(2+) , Mn^(2+) `
D. `Mn^(2+) , Co^(2+) , Ni^(2+) , Cu^(2+)`

Explanation

To determine the increasing order of paramagnetism for the given transition metal ions (Cu²⁺, Co²⁺, Mn²⁺, and Ni²⁺), we need to analyze the number of unpaired electrons in each ion. The more unpaired electrons an ion has, the stronger its paramagnetic character.

### Step-by-Step Solution:

1. **Identify the transition metal ions and their electronic configurations:**
- **Copper (Cu)**: Atomic number = 29
- Electronic configuration: \( \text{[Ar]} \, 3d^{10} \, 4s^1 \)
- For \( \text{Cu}^{2+} \): \( \text{[Ar]} \, 3d^9 \, 4s^0 \) (1 unpaired electron)

- **Cobalt (Co)**: Atomic number = 27
- Electronic configuration: \( \text{[Ar]} \, 3d^7 \, 4s^2 \)
- For \( \text{Co}^{2+} \): \( \text{[Ar]} \, 3d^7 \, 4s^0 \) (3 unpaired electrons)

- **Manganese (Mn)**: Atomic number = 25
- Electronic configuration: \( \text{[Ar]} \, 3d^5 \, 4s^2 \)
- For \( \text{Mn}^{2+} \): \( \text{[Ar]} \, 3d^5 \, 4s^0 \) (5 unpaired electrons)

- **Nickel (Ni)**: Atomic number = 28
- Electronic configuration: \( \text{[Ar]} \, 3d^8 \, 4s^2 \)
- For \( \text{Ni}^{2+} \): \( \text{[Ar]} \, 3d^8 \, 4s^0 \) (2 unpaired electrons)

2. **Count the number of unpaired electrons for each ion:**
- \( \text{Cu}^{2+} \): 1 unpaired electron
- \( \text{Co}^{2+} \): 3 unpaired electrons
- \( \text{Mn}^{2+} \): 5 unpaired electrons
- \( \text{Ni}^{2+} \): 2 unpaired electrons

3. **Rank the ions based on the number of unpaired electrons:**
- **Lowest paramagnetism**: \( \text{Cu}^{2+} \) (1 unpaired electron)
- **Next**: \( \text{Ni}^{2+} \) (2 unpaired electrons)
- **Next**: \( \text{Co}^{2+} \) (3 unpaired electrons)
- **Highest paramagnetism**: \( \text{Mn}^{2+} \) (5 unpaired electrons)

4. **Write the increasing order of paramagnetism:**
- \( \text{Cu}^{2+} < \text{Ni}^{2+} < \text{Co}^{2+} < \text{Mn}^{2+} \)

### Final Answer:
The increasing order of paramagnetism is:
\[ \text{Cu}^{2+} < \text{Ni}^{2+} < \text{Co}^{2+} < \text{Mn}^{2+} \]