What is the oxidation state of an individual sulfur atom in BaSO_4?

• A. 0
• B. +6
• C. +4
• D. -2

Answer: (B)

Verified step by step guidance

1. Identify the overall charge of the compound BaSO_4. Since BaSO_4 is a neutral compound, the sum of the oxidation states of all atoms must be zero.
2. Determine the oxidation state of barium (Ba). Barium is an alkaline earth metal and typically has an oxidation state of +2.
3. Assign the oxidation state of oxygen (O). Oxygen almost always has an oxidation state of -2 in compounds (except in peroxides or when bonded to fluorine). Since there are 4 oxygen atoms, their total contribution is 4 × (-2) = -8.
4. Let the oxidation state of sulfur (S) be x. Write the equation for the sum of oxidation states in the sulfate ion (SO_4^{2-}): x + 4(-2) = -2, because the sulfate ion has a charge of -2.
5. Solve the equation for x to find the oxidation state of sulfur: x - 8 = -2, so x = +6.