The number of unpaired electron in `Ni^(2+)` is

Options

A. 0
B. 2
C. 3
D. 4

Answer

To determine the number of unpaired electrons in the \( \text{Ni}^{2+} \) ion, we can follow these steps:

### Step 1: Determine the Atomic Number of Nickel
Nickel (Ni) has an atomic number of 28.

### Step 2: Write the Electronic Configuration of Neutral Nickel
The electronic configuration of neutral nickel can be written as:
\[ \text{Ni: } [\text{Ar}] \, 3d^8 \, 4s^2 \]
This means that nickel has 8 electrons in the 3d subshell and 2 electrons in the 4s subshell.

### Step 3: Determine the Electronic Configuration of \( \text{Ni}^{2+} \)
When nickel loses 2 electrons to form \( \text{Ni}^{2+} \), the electrons are removed first from the 4s subshell:
\[ \text{Ni}^{2+}: [\text{Ar}] \, 3d^8 \]
This configuration indicates that \( \text{Ni}^{2+} \) has 8 electrons in the 3d subshell.

### Step 4: Distribute the 3d Electrons
The 3d subshell can hold a maximum of 10 electrons. The distribution of the 8 electrons in the 3d subshell can be represented as follows:
- The 3d subshell has 5 orbitals (3dxy, 3dyz, 3dzx, 3dx²-y², 3dz²).
- According to Hund's rule, we fill each orbital singly before pairing them.

The filling of the 3d subshell with 8 electrons will look like this:
- 1 electron in each of the 5 orbitals (3dxy, 3dyz, 3dzx, 3dx²-y², 3dz²) → 5 electrons
- The remaining 3 electrons will pair up in the first three orbitals.

### Step 5: Count the Unpaired Electrons
After filling the 3d subshell:
- 3dxy: 2 electrons (paired)
- 3dyz: 2 electrons (paired)
- 3dzx: 2 electrons (paired)
- 3dx²-y²: 1 electron (unpaired)
- 3dz²: 1 electron (unpaired)

Thus, there are **2 unpaired electrons** in \( \text{Ni}^{2+} \).

### Final Answer
The number of unpaired electrons in \( \text{Ni}^{2+} \) is **2**.

---