The properties ofa chemical compound are dramatically different from the proper- e ties of the various elements comprising it. For example, sodium is a soft silvery metal that is extremely reactive and poisonous If you were to consume even a small amount of elemental sodium, you would need immediate medical attention. Chlo- rine, a green poisonous gas, is so toxic that it was used as a chemical weapon during World War I. Together, however, these elements produce sodium chloride, a harmless flavor enhancer that we call table salt. Thus, when elements combine to form compounds their properties change significantly.