Element, Chemical, is any substance that contains only one kind of atom. All chemical substances are elements or compounds (combinations of elements). For example, hydrogen and oxygen are elements, and water is a compound of hydrogen and oxygen. Oxygen and silicon are the most plentiful elements in Earth's crust, accounting for about 47 percent and 28 percent of the crust's mass (amount of matter), respectively.
The International Union of Pure and Applied Chemistry (IUPAC) is the recognized authority in crediting the discovery of elements and assigning names to them. For a discovery to be recognized by IUPAC, scientists must produce a sample of the element and measure certain of its properties. In addition, IUPAC prefers that another experiment confirm the discovery. IUPAC recognizes the existence of 111 elements. Scientists have also claimed the discovery of elements 112 through 116 and 118.
