Mercury is the only metal that is a liquid at room temperature. Mercury's chemical symbol is Hg. The "Hg" comes from the Greek word hydrargyrum, which means "liquid silver." Because of its silvery appearance and the way it moves, the metal was also called quicksilver. In fact, the chemical is named for the Roman god, Mercury, who was known for his speed and mobility. Students learn about the sources of mercury and its effects on the environment (coal-burning power plants are responsible for nearly 40 percent of the human-caused mercury emissions in the United States). They learn about mercury's chemical properties and classification as a transition metal. Mercury's place on the periodic table and its subatomic particles are also discussed. Readers will study mercury ions and isotopes. The book also explains the element's applications in thermometers, thermostats, silent wall switches, fluorescent lights, and dental amalgams.