The known elements are few in number. Ninety-two occur naturally in nature. In addition, spectroscopic analysis shows that technetium exists in the stars and particle accelerators have synthetically produced several other elements. In contrast, millions of compounds exist in nature and laboratory synthesis has produced many more.
Compounds consist of several different types of atoms. For example, water consists of molecules composed of oxygen and hydrogen atoms, and table salt consists of sodium ions and chlorine ions held together by electrical attraction. Other compounds, such as cellulose and starch, contain carbon, hydrogen and oxygen atoms. In contrast, each element is composed of only one type of atom. Some, like helium or argon, do not form molecules, but exist as independent uncombined atoms. Other elemental substances exist in the form of molecules. For example, chlorine gas consists of molecules in which two chlorine atoms unite with each other to form a bonded pair. In diamond and graphite, many carbon atoms unite with one another to form a large molecule. However, in all cases where elemental substances exist in the form of molecules, the molecules are made up of only one kind of atom.
Elements are simple. Chemical reactions can turn such elements as iron and tin into more complex substances, but it is not possible to degrade elements into simpler substances by chemical means. In contrast, chemical reactions can break down compounds into smaller units. For example, stomach juices hydrolyze proteins into peptides and electrolysis decomposes zinc chloride into zinc and chlorine.
Compounds may be either inorganic or organic. For example, cholesterol is an organic compound, while calcium carbonate is an inorganic compound. In contrast, all pure elements are inorganic substances. Moreover, elements make better targets in particle accelerators than compounds. For example, Berkeley scientists used elemental californium as a target when they synthesized seaborgium, and Russian scientists used elemental lead as a target when they tried to synthesize the same element.