The space model which is obtained by joining the points representing various bonded atoms gives the shape of the molecule. The geometry of the molecule is definite relative arrangement of the bonded atoms in a molecule. The shape and geometry of a molecule is explained by valence shell electron pair repulsion theory given by Gillespie and Nyholm.
Select the correct code for the following repulsion orders, according to VSEPR theory :
(I) lone pair -lone pair `gt` lone pair-bond pair
(II) lone pair-bond pair `gt` bond pair -bond pair
(III) lone pair -lone pair `gt` bond pair-bond pair
(IV) lone pair - bond pair `gt` lone pair-lone pair

Options

A. I,II and III
B. II and IV
C. I,II and IV
D. All

Answer

To solve the question regarding the repulsion orders according to VSEPR theory, we will analyze each statement one by one based on the principles of the theory.

### Step-by-Step Solution:

1. **Understanding VSEPR Theory**:
- VSEPR (Valence Shell Electron Pair Repulsion) theory states that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion. This includes both lone pairs and bonded pairs.

2. **Analyzing Statement I**:
- **Statement I**: Lone pair-lone pair repulsion > lone pair-bond pair repulsion.
- **Explanation**: Lone pairs occupy more space than bonding pairs because they are only associated with one nucleus. Therefore, this statement is **correct**.

3. **Analyzing Statement II**:
- **Statement II**: Lone pair-bond pair repulsion > bond pair-bond pair repulsion.
- **Explanation**: Since lone pairs exert more repulsion than bonding pairs, this statement is also **correct**.

4. **Analyzing Statement III**:
- **Statement III**: Lone pair-lone pair repulsion > bond pair-bond pair repulsion.
- **Explanation**: This statement is true because lone pair-lone pair repulsion is indeed greater than bond pair-bond pair repulsion. Thus, this statement is **correct**.

5. **Analyzing Statement IV**:
- **Statement IV**: Lone pair-bond pair repulsion > lone pair-lone pair repulsion.
- **Explanation**: This statement is incorrect because, as established, lone pair-lone pair repulsion is greater than lone pair-bond pair repulsion. Therefore, this statement is **incorrect**.

### Conclusion:
Based on the analysis:
- Statements I, II, and III are correct.
- Statement IV is incorrect.

### Final Answer:
The correct code for the repulsion orders according to VSEPR theory is **Option A: 1, 2, 3 statements are correct**.