An inter halogen compound `AB_3` has T shaped structure, how many lone pairs are present on 'A'

Options

A. 1
B. 2
C. 3
D. 4

Answer

To determine the number of lone pairs present on the central atom 'A' in the interhalogen compound \( AB_3 \) with a T-shaped structure, we can follow these steps:

### Step 1: Identify the Valence Electrons
- The central atom 'A' is a halogen, which means it has 7 valence electrons.
- Each halogen atom 'B' also has 7 valence electrons.

### Step 2: Count the Total Valence Electrons
- For the compound \( AB_3 \), we have:
- 1 atom of 'A' contributes 7 electrons.
- 3 atoms of 'B' contribute \( 3 \times 7 = 21 \) electrons.
- Total valence electrons = \( 7 + 21 = 28 \) electrons.

### Step 3: Draw the Lewis Structure
- In the T-shaped structure, the central atom 'A' is bonded to three 'B' atoms.
- Each bond between 'A' and 'B' involves 2 electrons (1 from 'A' and 1 from 'B').
- Since there are 3 bonds, the number of bonding electrons used = \( 3 \times 2 = 6 \) electrons.

### Step 4: Calculate Remaining Electrons
- Total electrons used in bonding = 6 electrons.
- Remaining electrons = Total valence electrons - Electrons used in bonding = \( 28 - 6 = 22 \) electrons.

### Step 5: Distribute Remaining Electrons as Lone Pairs
- The remaining 22 electrons will be used to form lone pairs on the central atom 'A'.
- Each lone pair consists of 2 electrons.
- Number of lone pairs on 'A' = Remaining electrons / 2 = \( 22 / 2 = 11 \) lone pairs.

### Step 6: Adjust for the T-Shaped Structure
- However, this calculation seems incorrect based on the T-shaped structure. In a T-shaped molecule, we need to consider the geometry and the fact that only 3 bonds are formed.
- The correct approach is to recognize that in the T-shaped structure, the central atom 'A' uses 3 of its valence electrons to bond with the 3 'B' atoms.
- Therefore, the number of electrons left for lone pairs = \( 7 - 3 = 4 \) electrons.

### Step 7: Calculate the Number of Lone Pairs
- Since each lone pair consists of 2 electrons, the number of lone pairs on 'A' = \( 4 / 2 = 2 \) lone pairs.

### Final Answer
- The number of lone pairs present on 'A' in the interhalogen compound \( AB_3 \) with a T-shaped structure is **2**.