Atomic and Nuclear PhysicsDOE-HDBK-1019/1-93ATOMIC NATURE OF MATTEREach type of atom that contains a unique combination ofFigure 2 Nomenclature forIdentifying Nuclidesprotons and neutrons is called a nuclide. Not allcombinations of numbers of protons and neutrons arepossible, but about 2500 specific nuclides with uniquecombinations of neutrons and protons have beenidentified. Each nuclide is denoted by the chemicalsymbol of the element with the atomic number written asa subscript and the mass number written as a superscript,as shown in Figure 2. Because each element has aunique name, chemical symbol, and atomic number, onlyone of the three is necessary to identify the element. Forthis reason nuclides can also be identified by either thechemical name or the chemical symbol followed by themass number (for example, U-235 or uranium-235).Another common format is to use the abbreviation of thechemical element with the mass number superscripted (for example, 235U). In this handbook theformat used in the text will usually be the element's name followed by the mass number. Inequations and tables, the format in Figure 2 will usually be used.Example:State the name of the element and the number of protons, electrons, and neutrons in thenuclides listed below.11H105B147N11448Cd23994PuRev. 0Page 5NP-01
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