Not a substance, a compound
Say that sulfur is simple
In fact, in the determination of the nature of a substance, the effect of impurities is generally ignored. The reason why hydrochloric acid is a mixture is because its essential composition is water and HCl, both of which are not impurities and sulfur, which is S8 (A kind of sulfur), there is no other necessary ingredients, so it is simple and some occasions, really want to consider impurities, but this will be a clear indication in the name such as copper or copper, copper are simple, Bronze, white copper because of the determination of other ingredients and for the mixture, while the coarse copper although the other ingredients are not sure, is impurity, but because there is a clear name prompt, but also the mixture
Yes, the elemental sulfur is commonly known as sulfur, which is a definition.
