Which of the following is correct ?

Options

A. During `N_2^+` formation, one electron is removed from the bonding molecular orbitals
B. During `O_2^+` formation, one electron is removed from the antibonding molecular orbitals
C. During `O_2^-` formation, one electron is added to the bonding molecular orbitals
D. During `CN^–` formation, one electron is added to the bonding molecular orbitals

Answer

To solve the question regarding which statements about molecular orbitals are correct, we will analyze the formation of the molecular species mentioned in the video transcript step by step.

### Step-by-Step Solution:

1. **Understanding Molecular Orbital Theory (MOT)**:
- Molecular Orbital Theory helps us understand the arrangement of electrons in molecules. Electrons occupy molecular orbitals that can be bonding or anti-bonding.

2. **Electron Count in N2**:
- Nitrogen (N) has an atomic number of 7, so N2 has a total of 14 electrons (7 from each N atom).
- The filling of molecular orbitals for N2 is as follows:
- σ1s (2), σ1s* (2), σ2s (2), σ2s* (2), π2px (2), π2py (2), σ2pz (2).
- Total: 2 + 2 + 2 + 2 + 2 + 2 = 14 electrons.

3. **Formation of N2+**:
- When forming N2+, one electron is removed. According to MOT, this electron is removed from the σ2pz bonding molecular orbital.
- Thus, N2+ has 13 electrons, and the filling is:
- σ1s (2), σ1s* (2), σ2s (2), σ2s* (2), π2px (2), π2py (2), σ2pz (1).
- Conclusion: It is correct that during N2 formation, one electron is removed from the bonding molecular orbital.

4. **Formation of O2**:
- Oxygen (O) has an atomic number of 8, so O2 has 16 electrons.
- The filling of molecular orbitals for O2 is:
- σ1s (2), σ1s* (2), σ2s (2), σ2s* (2), π2px (2), π2py (2), σ2pz (2).
- When forming O2+, one electron is removed from the π*2py or π*2px anti-bonding molecular orbitals.
- Conclusion: It is correct that during O2 formation, one electron is removed from the anti-bonding molecular orbital.

5. **Formation of O2-**:
- When O2 gains an electron to form O2-, it will fill the π*2py or π*2px anti-bonding orbital.
- Thus, one electron is added to the anti-bonding molecular orbital.
- Conclusion: This statement is correct.

6. **Formation of CN-**:
- CN has a total of 14 electrons (C has 6 and N has 7).
- The filling of molecular orbitals for CN- (adding one electron) will lead to the addition of an electron to the bonding molecular orbital.
- Conclusion: It is correct that during CN- formation, one electron is added to the bonding molecular orbital.

### Final Conclusion:
- All statements A, B, and D are correct based on the analysis of molecular orbital filling and electron transitions.