Chemical elements are substances composed of only one type of atom and they cannot be broken down further. Chemical elements are the simplest forms of matter and each one is assigned a specific atomic number. Check out these articles on chemical elements.
Niobium, a lustrous, silver-white, metallic chemical element. Until 1950, when the name niobium was officially adopted by the International Union of Pure and Applied Chemistry, the metal was also known as columbium in the United States. See more »
Plutonium, a radioactive, metallic chemical element. Although very small quantities of plutonium occur in nature in some uranium ores, virtually all plutonium in existence has been produced in nuclear reactors. See more »