- Sulfur dioxide (SO2): A toxic gas produced by burning fossil fuels and roasting sulfide ores, which can cause respiratory issues and contribute to acid rain.

- Sulfur trioxide (SO3): A highly reactive gas that is a precursor to sulfuric acid, mainly produced by converting sulfur dioxide in the presence of a catalyst.

- Sulfuric acid (H2SO4): A strong mineral acid widely used in various industries such as fertilizer production, petroleum refining, and metal processing. It is one of the most important industrial chemicals.

- Iron sulfide (FeS2): Also known as pyrite or fool's gold, this compound is commonly found in mineral ores and can be used to produce sulfuric acid.

- Hydrogen sulfide (H2S): A toxic, flammable gas with a distinct rotten egg odor, often associated with volcanic activity, natural gas, and wastewater treatment plants.

These compounds are found in various forms and have different properties and applications.