(a) The nitric oxide molecule, NO, readily loses one electron to form the NO⁺ ion. Which of the following is the best explanation of why this happens: (i) Oxygen is more electronegative than nitrogen, (ii) The highest energy electron in NO lies in a π_2p* molecular orbital, or (iii) The π_2p* MO in NO is completely filled.

Verified step by step guidance

1. Understand the concept of molecular orbitals (MOs) and how they relate to the stability of a molecule. In NO, the molecular orbitals are formed from the combination of atomic orbitals of nitrogen and oxygen.
2. Identify the highest energy molecular orbital in the NO molecule. In this case, it is the π2p* (pi star) molecular orbital, which is an antibonding orbital.
3. Recognize that electrons in antibonding orbitals decrease the stability of a molecule. Therefore, removing an electron from an antibonding orbital can increase the stability of the molecule.
4. Consider the electronic configuration of NO. The π2p* MO is partially filled, meaning it contains one electron. Removing this electron would result in a more stable configuration for the NO+ ion.
5. Evaluate the given options: (i) Oxygen's electronegativity does not directly explain the electron loss, (ii) The highest energy electron in NO lies in a π2p* MO, which is correct, and (iii) The π2p* MO in NO is not completely filled, so this is incorrect. Therefore, option (ii) is the best explanation.

Key Concepts

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. In the context of nitric oxide (NO), oxygen is more electronegative than nitrogen, which influences the distribution of electrons in the molecule. However, while this property affects bond polarity, it does not directly explain the ionization process of NO.

Molecular Orbitals

Molecular orbitals (MOs) are formed by the combination of atomic orbitals when atoms bond together. In NO, the highest energy electron occupies a π_2p* molecular orbital, which is an antibonding orbital. Electrons in antibonding orbitals are less stable and more likely to be lost, making this concept crucial for understanding why NO can readily lose an electron to form the NO⁺ ion.

Electron Configuration and Stability

The stability of an electron configuration plays a significant role in the ionization of molecules. In NO, the π_2p* MO is not completely filled, which contributes to the molecule's tendency to lose an electron. A partially filled antibonding orbital is less stable than a filled or lower-energy orbital, making the loss of an electron energetically favorable.