The bond order depends on the number of electrons in the bonding and antibonding orbitals. Which of the following statement is/are correct about bond order ?

Options

A. Bond order cannot have a negative value.
B. It always has an integral value
C. It is a nonzero quantity
D. It can assume any value-positive or negative, integral or fractional, including zero.

Answer

To solve the question regarding the bond order and its characteristics, we will analyze the statements provided and determine which ones are correct based on the principles of Molecular Orbital Theory (MOT).

### Step-by-Step Solution:

1. **Understanding Bond Order**:
Bond order is defined as the difference between the number of electrons in bonding molecular orbitals (nB) and the number of electrons in antibonding molecular orbitals (nA), divided by 2. The formula is:
\[ \text{Bond Order} = \frac{nB - nA}{2} \]

2. **Evaluating Statements**:
- **Statement 1**: "A bond order cannot have a negative value."
- This statement is **incorrect**. Bond order can be negative if there are more electrons in antibonding orbitals than in bonding orbitals (nA > nB).

- **Statement 2**: "It always has an integral value."
- This statement is **incorrect**. Bond order can be fractional, especially in cases where there are unpaired electrons in the molecular orbitals.

- **Statement 3**: "It is a non-zero quantity."
- This statement is **incorrect**. Bond order can be zero (when nB = nA), indicating an unstable molecule.

- **Statement 4**: "It can assume any positive value, negative, integral or fractional, including zero."
- This statement is **correct**. Bond order can indeed be positive, negative, integral, fractional, or zero.

3. **Conclusion**:
Based on the analysis, the only correct statement about bond order is the fourth one.

### Final Answer:
The correct statement about bond order is:
- It can assume any positive value, negative, integral or fractional, including zero.