Final answer:
The oxidation number of sulfur (S) in barium sulfate, BaSO₄, is +6.
Step-by-step explanation:
The oxidation number of sulfur (S) in barium sulfate, BaSO₄, can be determined using guidelines for assigning oxidation numbers. According to guideline 3, the oxidation number for oxygen is -2. With this information, we can use guideline 4 to calculate the oxidation number for sulfur.
Since each oxygen atom in BaSO₄ has an oxidation number of -2, and there are four oxygen atoms, the total oxidation number due to oxygen is -8. To find the oxidation number of sulfur, we need to equate the sum of the oxidation numbers to zero (since the compound is neutral). Therefore, the oxidation number of sulfur in BaSO₄ is +6.
It is important to note that the oxidation number of sulfur does not represent a charge on the sulfur atom; it is simply a way to apportion electrons among the atoms in the compound.