Periodic table three naturally occurring isotopes: all of its atoms have six protons and most have six neutrons as well, but about one per cent have seven neutrons, and a very small fraction have eight neutrons. Isotopes are never separated in the periodic table; they are always grouped together under a single element. Elements with no stable isotopes have the atomic masses of their most stable isotopes, where such masses are shown, listed in parentheses. In the standard periodic table, the elements are listed in order of increasing atomic number "Z" (the number of protons in the nucleus of an atom). A
History of the periodic table were "earth", "water", "air" and "fire". Similar ideas about these four elements also existed in other ancient traditions, such as Indian philosophy. The history of the periodic table is also a history of the discovery of the chemical elements. The first person in history to discover a new element was Hennig Brand, a bankrupt German merchant. Brand tried to discover the Philosopher's Stone — a mythical object that was supposed to turn inexpensive base metals into gold. In 1669 (or later), his experiments with distilled human urine resulted in the production of a glowing white substance, which he called "cold