The molecule `AB_n` is planar with six pairs of electrons around A in the valence shell. The value of n is

Answer

To determine the value of \( n \) in the molecule \( AB_n \) where \( A \) has six pairs of electrons in its valence shell and the molecule is planar, we can follow these steps:

### Step 1: Understand the electron pairs around atom A
Given that there are six pairs of electrons around atom \( A \), this means that the total number of electron pairs is \( 6 \). Each pair can either be a bond pair (shared between \( A \) and \( B \)) or a lone pair (not shared).

### Step 2: Determine hybridization
With six pairs of electrons, the hybridization of atom \( A \) can be determined. The hybridization corresponding to six electron pairs is \( sp^3d^2 \).

### Step 3: Identify the geometry
The geometry associated with \( sp^3d^2 \) hybridization is octahedral. However, since the molecule is specified to be planar, we need to consider the arrangements that can lead to a planar structure.

### Step 4: Analyze possible arrangements
1. **All bond pairs (6 bond pairs, 0 lone pairs)**: This would result in an octahedral shape, which is not planar.
2. **5 bond pairs and 1 lone pair**: This would give a square pyramidal shape, which is also not planar.
3. **4 bond pairs and 2 lone pairs**: This arrangement leads to a square planar shape, which is indeed planar.

### Step 5: Calculate the value of \( n \)
In the square planar arrangement, there are 4 bond pairs. Therefore, the value of \( n \) (the number of \( B \) atoms around \( A \)) is \( 4 \).

### Conclusion
Thus, the value of \( n \) is \( 4 \).

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