To determine which of the given elements has the most unpaired d-electrons, we will follow these steps:
### Step 1: Identify the Elements
We will consider the following elements and their respective ions:
- Zinc (Zn)
- Iron (Fe)
- Nickel (Ni)
- Copper (Cu)
### Step 2: Write the Electronic Configurations
Next, we will write the electronic configurations for each of these elements:
- **Zinc (Zn)**: \( \text{[Ar]} \, 4s^2 \, 3d^{10} \)
- **Iron (Fe)**: \( \text{[Ar]} \, 4s^2 \, 3d^6 \)
- **Nickel (Ni)**: \( \text{[Ar]} \, 4s^2 \, 3d^8 \)
- **Copper (Cu)**: \( \text{[Ar]} \, 4s^2 \, 3d^9 \) or \( \text{[Ar]} \, 4s^1 \, 3d^{10} \) (due to electron configuration stability)
### Step 3: Determine the Electronic Configurations of Ions
Now, we will determine the electronic configurations for the respective ions:
- **Zinc Ion (Zn²⁺)**: Loses 2 electrons from the 4s orbital, resulting in \( \text{[Ar]} \, 3d^{10} \)
- **Iron Ion (Fe²⁺)**: Loses 2 electrons from the 4s orbital, resulting in \( \text{[Ar]} \, 3d^6 \)
- **Nickel Ion (Ni³⁺)**: Loses 2 electrons from the 4s orbital and 1 from the 3d orbital, resulting in \( \text{[Ar]} \, 3d^7 \)
- **Copper Ion (Cu⁺)**: Loses 1 electron from the 4s orbital, resulting in \( \text{[Ar]} \, 3d^{10} \)
### Step 4: Count the Unpaired d-Electrons
Next, we will count the number of unpaired d-electrons for each ion:
- **Zn²⁺ (3d¹⁰)**: 0 unpaired electrons (all paired)
- **Fe²⁺ (3d⁶)**: 4 unpaired electrons (electrons are distributed as ↑↓ ↑↓ ↑ ↑)
- **Ni³⁺ (3d⁷)**: 3 unpaired electrons (electrons are distributed as ↑↓ ↑↓ ↑ ↑ ↑)
- **Cu⁺ (3d¹⁰)**: 0 unpaired electrons (all paired)
### Step 5: Conclusion
From the counts of unpaired d-electrons:
- Zn²⁺: 0 unpaired electrons
- Fe²⁺: 4 unpaired electrons
- Ni³⁺: 3 unpaired electrons
- Cu⁺: 0 unpaired electrons
The element with the most unpaired d-electrons is **Fe²⁺**, which has **4 unpaired d-electrons**.
### Final Answer
**Fe²⁺ has the most unpaired d-electrons (4 unpaired electrons).**
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