Identify the pair of molecules in which the central atom of the first molecule has exactly 7 electrons in its valence shell, and the central atom of the second molecule has exactly 12 electrons in its valence shell.

Step-by-step solution

To find the number of electrons in the valence shell of the central atom, we count the bonding and non-bonding electrons in their Lewis structures. In ClO ₂ , the central Cl atom forms two double bonds with oxygen and has one lone pair and one odd electron. Total electrons on Cl = 8 (bonding) + 2 (lone pair) + 1 (odd) = 11 . In PCl ₅ , P forms 5 single bonds. Total electrons on P = 10 . In BF ₃ , B forms 3 single bonds. Total electrons on B = 6 (incomplete octet). In SF ₆ , S forms 6 single bonds. Total electrons o