Sulfur is bright yellow in its solid elemental form, red in its liquid form and burns with a blue flame. Compounds containing sulfur can appear red, green, brown or gray.
Sulfur is a non-metal with 16 protons, making it the 16th element on the periodic table. Sulfur was first classified as a lone element by Antoine Lavoisier in 1789, but people have had knowledge of it and have used it for thousands of years. In the Bible sulfur was known as brimstone. Sulfur can be present in the human body, but certain forms of it are toxic and can lead to death if ingested.