In a neutral compound, the sum of the oxidation numbers is

• A. 0
• B. 1
• C. -1
• D. The total number of atoms

Answer: (A)

When assigning oxidation numbers, the total must balance to the overall charge of the species. For a neutral compound, that overall charge is zero, so the oxidation numbers must sum to zero. This is why simple examples fit: in water, each hydrogen is +1 and oxygen is -2, giving +2 + (-2) = 0. In sodium chloride, sodium is +1 and chloride is -1, again totaling 0. The other possibilities don’t fit because a net charge of +1 or -1 would indicate the substance is charged (an ion), not neutral. The total number of atoms has no direct relation to the oxidation-number sum.