Substance composed of atoms, each of which has the same A number equivalent to the number of protons in the nucleus of an atom, commonly abbreviated as Z. (Z) and chemical properties. The chemical properties of an element are determined by the arrangement of the electrons in the various shells (specified by their quantum number) that surround the Core of an atom, where nearly the entire mass and all positive charge is concentrated. It consists of protons and neutrons.. In a neutral atom, the number of orbiting electrons is equal to the number of protons in its nucleus. Each chemical element is denoted by a symbol, which may be amplified by the addition of the Mass of a neutral atom of a nuclide - also called "atomic weight." The atomic weight of an element is the weighted average of each isotope. (A) as a superscript (4He).
Some or all content above used with permission from J. H. Wittke.