What is the oxidation number of sulfur in S8?

• A. 0
• B. +8
• C. -2
• D. +2

Answer: (A)

The main concept here is how to assign oxidation numbers in an elemental substance. In the elemental form, atoms have oxidation numbers of zero. S8 is a ring of sulfur atoms bonded to each other with identical electronegativity, so electrons are shared rather than transferred and the molecule has no net charge. That means each sulfur atom has an oxidation state of 0, so the oxidation number of sulfur in S8 is zero. In compounds sulfur can show other oxidation states, such as -2 in sulfide or +6 in sulfate, but those states arise from bonds with other elements, not in the pure elemental form like S8.