Which is correct statement ?
As the s-character of a hybrid orbital decreases
(I) The bond angle decreases (II) The bond strength increases
(III) The bond length increases (IV) Size of orbitals increases

Options

A. I, III and IV
B. II, III and IV
C. I and II
D. all are correct

Answer

To solve the question regarding the correct statement about the relationship between s-character of hybrid orbitals and various properties, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding s-character and hybridization**:
- Hybrid orbitals are formed by the mixing of atomic orbitals. The s-character refers to the proportion of s orbital character in the hybrid orbital.
- For example, in sp hybridization, there is 50% s-character and 50% p-character, while in sp3 hybridization, there is 25% s-character and 75% p-character.

2. **Analyzing Option (I): The bond angle decreases**:
- As the s-character decreases, the bond angle also decreases.
- For example:
- sp hybridization has a bond angle of 180°.
- sp2 hybridization has a bond angle of 120°.
- sp3 hybridization has a bond angle of 109.5°.
- Therefore, this statement is **correct**.

3. **Analyzing Option (II): The bond strength increases**:
- The bond strength is related to the type of hybridization.
- sp hybridized bonds (triple bonds) are stronger than sp2 (double bonds), which are stronger than sp3 (single bonds).
- As the s-character decreases, the bond strength actually **decreases**. Thus, this statement is **incorrect**.

4. **Analyzing Option (III): The bond length increases**:
- As the s-character decreases, the bond length increases.
- This is because sp hybridized bonds are shorter than sp2, which are shorter than sp3.
- Therefore, this statement is **correct**.

5. **Analyzing Option (IV): Size of orbitals increases**:
- The size of the hybrid orbitals increases as the s-character decreases.
- This is because s orbitals are smaller than p orbitals, and thus sp hybrid orbitals are smaller than sp2, which are smaller than sp3.
- Therefore, this statement is **correct**.

### Conclusion:
Based on the analysis:
- Option (I) is correct: The bond angle decreases.
- Option (II) is incorrect: The bond strength does not increase.
- Option (III) is correct: The bond length increases.
- Option (IV) is correct: The size of orbitals increases.

Thus, the correct statements are (I), (III), and (IV).