Below is one of the molecular orbitals of $HF$. Which of the following best describes the orbital?

• A. A bonding molecular orbital formed by the overlap of the $H{1}_s$ and $F{2}_p$ orbitals
• B. A bonding molecular orbital formed by the overlap of two $H{1}_s$ orbitals
• C. An antibonding molecular orbital formed by the overlap of two $F{2}_p$ orbitals
• D. A nonbonding molecular orbital localized on the fluorine atom

Answer: (A)

Verified step by step guidance

1. Identify the atoms involved in the molecule HF: hydrogen (H) and fluorine (F). Recognize that hydrogen has a 1s atomic orbital and fluorine has 2p atomic orbitals as its valence orbitals.
2. Recall that molecular orbitals (MOs) form by the linear combination of atomic orbitals (LCAO). The type of MO formed depends on the symmetry and energy compatibility of the overlapping atomic orbitals.
3. Consider the possible overlaps: H 1s with F 2p orbitals can form bonding or antibonding molecular orbitals. Overlap between two H 1s orbitals is not possible here since there is only one hydrogen atom. Overlap between two F 2p orbitals would require two fluorine atoms, which is not the case.
4. Determine the nature of the molecular orbital by examining the phase and electron density distribution: a bonding molecular orbital results from constructive interference (in-phase overlap) between the H 1s and F 2p orbitals, leading to increased electron density between the nuclei.
5. Conclude that the molecular orbital shown is best described as a bonding molecular orbital formed by the overlap of the H 1s and F 2p orbitals, since this matches the atomic orbitals present and the bonding interaction in HF.