Element

Name:
Element
Detailed information:
One of the 112 presently known kinds of substances that compose all matter at and above the atomic level. According to a theory that has gained acceptance, the lightest elements were formed in less than half an hour from a primordial complex called ylem, a mixture of neutrons and electromagnetic radiation. The smallest unit of any element is the atom. All the atoms of a given element are identical in nuclear charge and number of electrons and protons, but they may differ in mass, e.g., hydrogen has mass numbers of 1, 2, and 3, called hydrogen, deuterium, and tritium, respectively. These are the isotopes of hydrogen; most elements have isotopic forms that are due to the presence of one or more extra neutrons in the nucleus. The atomic number of an element indicates its position in the periodic table and represents the number of protons present, which is the same as the number of electrons. All elements heavier than lead are unstable and radioactive. About 90% of the earth's crust is made up of elements with even numbers of protons and neutrons. No stable elements heavier than nitrogen have an odd number of both protons and neutrons. Elements of even atomic number normally have several isotopes, while those of odd atomic number never have more than two stable isotopes. All elements beyond uranium (transuranic) were nonexistent in 1940. They are artificially created by bombardment of other elements with neutrons or other heavy particles. Research on new elements is actively carried on at many laboratories including the Lawrence Livermore Laboratories, which reported discovery of element 106 in 1974. Creation of element 109 was announced in 1982, and of element 112 in 1996. A single atom of element 109 was made by West German physicists by bombarding ²⁰⁹Bi with ⁵⁸Fe nuclei. Controversy continues on the naming of elements 104 through 109. Many more (possibly up to 150) are theoretically possible according to Dr. G. T. Seaborg.See Periodic Table; Isotope; Radioactivity; Abundance.Note: For origin of elements, see Nucleogenesis.