Which molecule is represented by a molecular orbital diagram showing 10 electrons filling the following orbitals in order: σ(1s), σ*(1s), σ(2s), σ*(2s), and σ(2p)?

• A. N2
• B. F2
• C. O2
• D. C2

Answer: (B)

Verified step by step guidance

1. Identify the total number of electrons in the molecule based on the molecular orbital diagram. The diagram shows 10 electrons filling the orbitals in the order: \(\sigma(1s)\), \(\sigma^*(1s)\), \(\sigma(2s)\), \(\sigma^*(2s)\), and \(\sigma(2p)\).
2. Recall the electron configuration of diatomic molecules in molecular orbital theory. The \$1s\( and \)2s\( orbitals (and their antibonding counterparts) account for core and inner valence electrons, while the \)2p$ orbitals accommodate the valence electrons that determine bonding properties.
3. Sum the electrons in the given orbitals: \(\sigma(1s)\) and \(\sigma^*(1s)\) each hold 2 electrons, \(\sigma(2s)\) and \(\sigma^*(2s)\) each hold 2 electrons, and \(\sigma(2p)\) holds the remaining electrons. This totals 10 electrons.
4. Match the total number of electrons to the atomic numbers of the diatomic molecules listed: \(N_2\) has 14 electrons, \(F_2\) has 18 electrons, \(O_2\) has 16 electrons, and \(C_2\) has 12 electrons. Since the diagram shows only 10 electrons, consider that the diagram might represent only valence electrons or a simplified model.
5. Recognize that the molecular orbital filling order changes for molecules with atomic numbers less than 8 (like \(C_2\) and \(N_2\)) compared to those with higher atomic numbers (like \(O_2\) and \(F_2\)). The presence of \(\sigma(2p)\) before \(\pi(2p)\) orbitals suggests the molecule is from the second period with atomic number 9 or 10, consistent with \(F_2\).