Which of the following is `(are)` correct statements ? .

Options

A. Probability of finding the electron in bonding `MO` is more than combining atomic orbitals .
B. Bonding `MO' s` are formed when same sign of orbitals overlap
C. d-d combination of atomic orbitals gives delta and delta^(**) `MO's` .
D. None of these

Answer

To determine which statements are correct regarding molecular orbitals, we will analyze each statement step by step.

### Step 1: Analyze the First Statement
**Statement 1:** The probability of finding the electron in bonding molecular orbitals (MOs) is more than in combining atomic orbitals.

**Explanation:**
- Molecular Orbital Theory (MOT) states that atomic orbitals combine to form molecular orbitals.
- Electrons in bonding MOs are more stable and have a higher probability of being found between the nuclei of the bonded atoms compared to the original atomic orbitals.
- Therefore, this statement is **correct**.

### Step 2: Analyze the Second Statement
**Statement 2:** A bonding molecular orbital is formed when the same sign of orbitals overlap.

**Explanation:**
- Bonding MOs are formed by the constructive interference (addition) of atomic orbitals, which occurs when the wave functions of the orbitals have the same sign.
- This results in an increase in electron density between the nuclei, which stabilizes the bond.
- Hence, this statement is also **correct**.

### Step 3: Analyze the Third Statement
**Statement 3:** The combination of d atomic orbitals gives delta (δ) and delta star (δ*) molecular orbitals.

**Explanation:**
- In molecular orbital theory, d orbitals can combine to form molecular orbitals, including delta (δ) and delta star (δ*) orbitals, which are typically associated with more complex bonding scenarios.
- However, this statement is somewhat misleading as it suggests a specific pairing that is not universally applicable. The combination of d orbitals can lead to various types of molecular orbitals depending on the symmetry and the specific atoms involved.
- Therefore, this statement is **not entirely correct**.

### Step 4: Analyze the Fourth Statement
**Statement 4:** The bond order is defined as half the difference between the number of electrons present in bonding and anti-bonding orbitals.

**Explanation:**
- The bond order is indeed calculated using the formula:
\[ \text{Bond Order} = \frac{(N_b - N_a)}{2} \]
where \(N_b\) is the number of electrons in bonding orbitals and \(N_a\) is the number of electrons in anti-bonding orbitals.
- This definition is accurate, making this statement **correct**.

### Conclusion
Based on the analysis:
- **Correct Statements:** 1, 2, and 4.
- **Incorrect Statement:** 3.

### Final Answer
The correct statements are A, B, and D.

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