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 provided in the question and determine their correctness based on the principles of VSEPR 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 to minimize repulsion between them. This includes both lone pairs and bonding pairs.

2. **Analyzing the Given Statements**:
- **(I) Lone pair - lone pair > Lone pair - bond pair**:
- Lone pairs occupy more space than bonding pairs due to their higher electron density. Therefore, the repulsion between two lone pairs is indeed greater than that between a lone pair and a bond pair. This statement is **correct**.

- **(II) Lone pair - bond pair > Bond pair - bond pair**:
- A lone pair exerts more repulsion than a bond pair because it occupies more space. Thus, the repulsion between a lone pair and a bond pair is greater than that between two bond pairs. This statement is **correct**.

- **(III) Lone pair - lone pair > Bond pair - bond pair**:
- This is consistent with the previous points. Lone pair-lone pair repulsion is the strongest, followed by lone pair-bond pair, and then bond pair-bond pair. This statement is **correct**.

- **(IV) Lone pair - bond pair > Lone pair - lone pair**:
- This statement contradicts the earlier conclusions. Lone pair-lone pair repulsion is greater than lone pair-bond pair repulsion. Therefore, this statement is **incorrect**.

3. **Conclusion**:
- The correct statements according to VSEPR theory are (I), (II), and (III). The incorrect statement is (IV).

### Final Answer:
The correct code for the repulsion orders according to VSEPR theory is: **(I), (II), (III)**.

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