The shape of a moleculs is determined by electron pair repulsions in the valence shell A.lp occupies a larger space than a bp because it is not shared by two nuclei The the lp lp repulsion is greater than the lp-bp repulsion, which in trun is greater the bp-bp repulsion. The presence of lp causes distortion of bond angles hence, a daviation from an ideal shape THe extent of distortion depends upon the orientation of the lp's around the central atom In a trigonal bipyramid, the lp's occupy equatorial positions than the apical ones In `AB_(n)` type molecules, as the `EN` of A increases, the bp's come closer and the repulsion between them increases. On the other hand, as `EN` of `B` increases, the lp s get farther and repulsion decreases
In which of the following molecules is the bond angle largest ? .

Options

A. `PF_(3)`
B. `PCl_(3)`
C. `PBr_(3)`
D. `PI_(3)`

Explanation

To determine which molecule has the largest bond angle based on the information provided, we can follow these steps:

### Step 1: Understand the Role of Lone Pairs and Bond Pairs
- Lone pairs (lp) occupy more space than bond pairs (bp) because they are not shared between two nuclei. This leads to greater repulsion between lone pairs compared to bond pairs.

### Step 2: Analyze the Repulsion Sequence
- The order of repulsion strength is:
- lp-lp > lp-bp > bp-bp
- This means that lone pairs will distort bond angles more than bond pairs will.

### Step 3: Consider the Geometry of Molecules
- In a trigonal bipyramidal arrangement, lone pairs prefer equatorial positions over axial positions to minimize repulsion.

### Step 4: Evaluate Electronegativity Effects
- In ABn type molecules, as the electronegativity (EN) of A increases, bond pairs come closer together, increasing their repulsion.
- Conversely, as the EN of B increases, lone pairs move farther away, decreasing their repulsion.

### Step 5: Identify the Group of Elements
- The question involves comparing molecules with different surrounding atoms (B) from the same group (Group 17: F, Cl, Br, I).
- As we move down the group, electronegativity decreases.

### Step 6: Determine Bond Angle Trends
- As electronegativity decreases (moving from F to I), the bond angle increases.
- Therefore, the molecule with the least electronegativity surrounding atom will have the largest bond angle.

### Step 7: Compare the Given Molecules
- If we consider molecules like PF3, PCl3, PBr3, and PI3:
- Iodine (I) has the lowest electronegativity among these elements, thus PI3 will have the largest bond angle.

### Conclusion
- The molecule with the largest bond angle is **PI3**.