Final answer:
The central carbon atom in the structure CH3-C?-CH3 requires two hydrogen atoms to complete its four bonds, leading to the molecular formula C3H8.
Step-by-step explanation:
When evaluating the structure CH3-C?-CH3, we are trying to determine the number of hydrogen atoms required to complete the carbon's valence. Carbon atoms always form four bonds, whether they're with other carbon atoms or with hydrogen atoms. In the given structure, the central carbon atom (indicated by the question mark) is already bonded to two carbon atoms (each CH3 group provides one bond). Therefore, it still needs two additional bonds to complete its valence shell.
Since hydrogen forms only a single bond, the central carbon atom will need two hydrogen atoms to satisfy the carbon's four-bond requirement. Now, each carbon atom is bonded four times, ensuring the stability of the structure. In turn, the molecular formula of the compound would be C3H8, indicating a propane molecule with all carbon atoms having four bonds.