Which of the following complex compounds will exhibit highest paramagnetic behaviour ?
(At. No. : Ti = 22, Cr= 24, Co=27, Zn=30)

Options

A. `[Ti(NH_3)_6]^(3+)`
B. `[Cr(NH_3)_6]^(3+)`
C. `[Co(NH_3)_6]^(3+)`
D. `[Zn(NH_3)_6]^(2+)`

Explanation

To determine which of the given complex compounds exhibits the highest paramagnetic behavior, we need to analyze the number of unpaired electrons in each complex. The more unpaired electrons a compound has, the stronger its paramagnetic behavior will be.

### Step-by-Step Solution:

1. **Identify the Complexes and Their Metal Ions:**
- Titanium (Ti) with atomic number 22
- Chromium (Cr) with atomic number 24
- Cobalt (Co) with atomic number 27
- Zinc (Zn) with atomic number 30

2. **Determine the Oxidation States:**
- For Titanium in the complex, the oxidation state is +3.
- For Chromium in the complex, the oxidation state is +3.
- For Cobalt in the complex, the oxidation state is +3.
- For Zinc in the complex, the oxidation state is +2.

3. **Write the Electron Configurations:**
- **Titanium (Ti):**
- Ground state: [Ar] 3d² 4s²
- For Ti³⁺: [Ar] 3d¹ (removing 2 electrons from 4s and 1 from 3d)
- **Chromium (Cr):**
- Ground state: [Ar] 3d⁵ 4s¹
- For Cr³⁺: [Ar] 3d³ (removing 1 electron from 4s and 2 from 3d)
- **Cobalt (Co):**
- Ground state: [Ar] 3d⁷ 4s²
- For Co³⁺: [Ar] 3d⁶ (removing 2 electrons from 4s and 1 from 3d)
- **Zinc (Zn):**
- Ground state: [Ar] 3d¹⁰ 4s²
- For Zn²⁺: [Ar] 3d¹⁰ (removing 2 electrons from 4s)

4. **Count the Unpaired Electrons:**
- **Ti³⁺:** 1 unpaired electron (3d¹)
- **Cr³⁺:** 3 unpaired electrons (3d³)
- **Co³⁺:** 0 unpaired electrons (3d⁶, strong field ligand causes pairing)
- **Zn²⁺:** 0 unpaired electrons (3d¹⁰)

5. **Determine the Highest Paramagnetic Behavior:**
- Among the complexes, Cr³⁺ has the highest number of unpaired electrons (3 unpaired electrons), making it the most paramagnetic.

### Conclusion:
The complex that exhibits the highest paramagnetic behavior is the one containing Chromium (Cr³⁺).