What Is the Difference Between Fluorine and Fluoride?

First off, it's fluorine and fluoride and not flourine and flouride. The misspelling is common, but the "u" comes before the "o" in both. Fluorine is a chemical element. In pure form, it is a highly toxic, reactive, yellowish-green gas. The fluorine anion, F^-, or any of the compounds containing the anion are termed fluorides. When you hear about fluoride in drinking water, it comes from adding a fluorine compound (usually sodium fluoride, sodium fluorosilicate, or fluorosilicic acid) to drinking water, which dissociates to release the F^- ion. Stable fluorides are also found in fluoridated toothpaste and mouthwash.