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
The Periodic Table (short story collection) The Periodic Table (short story collection) The Periodic Table () is a collection of short stories by Primo Levi, published in 1975, named after the periodic table in chemistry. In 2006, the Royal Institution of Great Britain named it the best science book ever. The stories are autobiographical episodes of the author's experiences as a Jewish-Italian doctoral-level chemist under the Fascist regime and afterwards. They include various themes that follow a chronological sequence: his ancestry, his study of chemistry and practising the profession in wartime Italy, a pair of imaginative tales he wrote at that time, and his subsequent experiences