What is the sum of the oxidation numbers of all atoms in a neutral molecule of magnesium sulfate (MgSO_4)?

• A. -2
• B. +2
• C. 0
• D. +6

Answer: (C)

Verified step by step guidance

1. Recall that the sum of the oxidation numbers of all atoms in a neutral molecule must be zero because the molecule has no overall charge.
2. Identify the oxidation number of magnesium (Mg) in magnesium sulfate (MgSO_4). Since Mg is an alkaline earth metal, it typically has an oxidation number of +2.
3. Recognize that sulfate (SO_4) is a polyatomic ion with an overall charge of -2. In the sulfate ion, sulfur (S) has an oxidation number of +6, and each oxygen (O) has an oxidation number of -2.
4. Calculate the total oxidation number for the sulfate ion by summing the oxidation numbers of sulfur and four oxygens: +6 + 4(-2) = -2, which balances the +2 from magnesium.
5. Add the oxidation numbers of magnesium (+2) and sulfate (-2) to confirm the sum is zero, consistent with the molecule being neutral.