Identify the pair of molecules in which one of them is a molecule with an odd electron and the other has an expanded octet.

Step-by-step solution

A molecule with an odd electron is a radical containing an unpaired electron. NO has 5 + 6 = 11 valence electrons, which is an odd number, making it an odd-electron molecule. An expanded octet occurs when the central atom has more than 8 electrons in its valence shell. In PF ₅ , the phosphorus atom is bonded to 5 fluorine atoms, resulting in 5 2 = 10 electrons around the central phosphorus atom, which is an expanded octet. Checking other options: BCl ₃ has an incomplete octet (6 electrons). NO ₂ is an odd-electron