Which of the following statement is not correct ?

Options

A. Double bond is shorter than a single bond
B. Sigma bond is weaker than a `pi`-bond
C. Double bond is stronger than a single bond
D. Covalent bond is stronger than hydrogen bond

Explanation

To determine which statement is not correct, we will analyze each option one by one.

### Step 1: Analyze Option A
**Statement**: "Double bond is shorter than a single bond."
- **Explanation**: This statement is correct. Double bonds involve the sharing of two pairs of electrons between two atoms, which results in a stronger attraction that pulls the atoms closer together compared to a single bond, which involves only one pair of electrons. Therefore, double bonds are indeed shorter than single bonds.

### Step 2: Analyze Option B
**Statement**: "Sigma bond is weaker than a Pi bond."
- **Explanation**: This statement is incorrect. Sigma bonds are generally stronger than pi bonds. A sigma bond is formed by the head-on overlap of atomic orbitals, which allows for a greater overlap and thus a stronger bond. In contrast, pi bonds are formed by the side-to-side overlap of p orbitals, which is less effective. Therefore, this statement is not correct.

### Step 3: Analyze Option C
**Statement**: "Double bond is stronger than a single bond."
- **Explanation**: This statement is correct. Double bonds involve the sharing of more electrons (two pairs) compared to single bonds (one pair), which makes them stronger. Double bonds provide greater stability to molecules and restrict rotation around the bond axis.

### Step 4: Analyze Option D
**Statement**: "Covalent bond is stronger than hydrogen bond."
- **Explanation**: This statement is correct. Covalent bonds involve the sharing of electron pairs between atoms, resulting in a strong bond with high bond energy. In contrast, hydrogen bonds are weaker interactions that occur due to electrostatic attractions between a hydrogen atom and an electronegative atom. Thus, covalent bonds are indeed stronger than hydrogen bonds.

### Conclusion
After analyzing all the options, we find that the statement that is not correct is **Option B**: "Sigma bond is weaker than a Pi bond."

### Final Answer
The answer to the question is **Option B**.

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