Which of these species has same number of unpaired electrons with weak field as well as with strong field ligands.

Options

A. `Ti^(2+)`
B. `Cr^(3+)`
C. `Ni^(2+)`
D. All of these

Answer

To solve the problem of determining which species has the same number of unpaired electrons with both weak field and strong field ligands, we will follow these steps:

### Step 1: Identify the Species
We need to analyze the electronic configurations of the given species. The question mentions titanium (Ti) and chromium (Cr), so we will focus on these two.

### Step 2: Determine the Electron Configuration of Titanium (Ti²⁺)
- Titanium in its ground state has the electron configuration:
- Ti: [Ar] 4s² 3d⁰
- For Ti²⁺, we remove two electrons from the 4s orbital:
- Ti²⁺: [Ar] 3d²
- In the presence of weak field ligands, the 3d electrons will fill singly before pairing (Hund's rule). Thus, we have:
- Weak field: 3d² → 2 unpaired electrons
- In the presence of strong field ligands, the same filling occurs, and we still have:
- Strong field: 3d² → 2 unpaired electrons

### Step 3: Determine the Electron Configuration of Chromium (Cr³⁺)
- Chromium in its ground state has the electron configuration:
- Cr: [Ar] 4s² 3d⁵
- For Cr³⁺, we remove three electrons (two from 4s and one from 3d):
- Cr³⁺: [Ar] 3d³
- In the presence of weak field ligands, the filling will also follow Hund's rule:
- Weak field: 3d³ → 3 unpaired electrons
- In the presence of strong field ligands, the filling remains the same:
- Strong field: 3d³ → 3 unpaired electrons

### Step 4: Compare the Unpaired Electrons
- For Ti²⁺: 2 unpaired electrons (both weak and strong field)
- For Cr³⁺: 3 unpaired electrons (both weak and strong field)

### Conclusion
The species that has the same number of unpaired electrons with both weak field and strong field ligands is **Titanium (Ti²⁺)**, which has 2 unpaired electrons in both cases.