For 10 points, name this yellow element that forms a very poisonous, explosive, and rotten-egg-stinky gas with hydrogen.
An oxyanion of this element is found in alum. Two compounds of this element form oleum. An oxyacid of this element is often formed with a vanadium-five-oxide catalyst. Analogues of alcohols with it instead of oxygen are called thiols. Two atoms of this element in nearby cysteine molecules form a "bridge." Its elemental form is a crumbly solid made of (*) eight-membered rings. A diprotic acid containing this element is formed by the contact and lead chamber processes. It is added to rubber in vulcanization. For 10 points, name this yellow element that forms a very poisonous, explosive, and rotten-egg-stinky gas with hydrogen.
An oxyanion of this element is found in alum. Two compounds of this element form oleum.
sulfur [accept S]