Which one of the following transition metal ions is paramagnetic?

Options

A. `Au^(+)`
B. `Zn^(2+)`
C. `Cu^(2+)`
D. `Ag^(+)`

Explanation

To determine which transition metal ion is paramagnetic among the given options, we need to analyze the electronic configurations of each ion and check for the presence of unpaired electrons. Paramagnetism arises from the presence of unpaired electrons in an atom or ion.

### Step-by-Step Solution:

1. **Identify the Electronic Configurations**:
We need to find the electronic configurations of the given transition metal ions:
- Gold (Au⁺)
- Zinc (Zn²⁺)
- Copper (Cu²⁺)
- Silver (Ag⁺)

2. **Determine the Atomic Numbers**:
- Gold (Au): Atomic number 79
- Zinc (Zn): Atomic number 30
- Copper (Cu): Atomic number 29
- Silver (Ag): Atomic number 47

3. **Write the Electronic Configurations**:
- **Gold (Au)**: The electronic configuration is [Xe] 4f¹⁴ 5d¹⁰ 6s¹. For Au⁺, it loses one electron from the 6s orbital:
- Au⁺: [Xe] 4f¹⁴ 5d¹⁰ (10 d-electrons, no unpaired electrons).
- **Zinc (Zn)**: The electronic configuration is [Ar] 3d¹⁰ 4s². For Zn²⁺, it loses two electrons from the 4s orbital:
- Zn²⁺: [Ar] 3d¹⁰ (10 d-electrons, no unpaired electrons).
- **Copper (Cu)**: The electronic configuration is [Ar] 3d¹⁰ 4s². For Cu²⁺, it loses two electrons (one from 4s and one from 3d):
- Cu²⁺: [Ar] 3d⁹ (9 d-electrons, 1 unpaired electron).
- **Silver (Ag)**: The electronic configuration is [Kr] 4d¹⁰ 5s¹. For Ag⁺, it loses one electron from the 5s orbital:
- Ag⁺: [Kr] 4d¹⁰ (10 d-electrons, no unpaired electrons).

4. **Analyze the Results**:
- Au⁺: No unpaired electrons (d¹⁰).
- Zn²⁺: No unpaired electrons (d¹⁰).
- Cu²⁺: 1 unpaired electron (d⁹).
- Ag⁺: No unpaired electrons (d¹⁰).

5. **Conclusion**:
The only ion with unpaired electrons is Cu²⁺, which makes it paramagnetic.

### Final Answer:
The transition metal ion that is paramagnetic is **Copper (Cu²⁺)**.