Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERING©A COMMON HYDROGEN B DEUTERIUM C TRITIUMFigure 24-3.— Isotopes of hydrogen.5.40(147A)the symbol of the element is the atomic massnumber; thus the superscript indicates whichisotope of the element is being referred to.The geneal symbol for any atom is thusZXAwhereX symbol of the elementZ atomic number (number of protons)A atomic mass number (sum of the numberof protons and the number of neutrons)Of the known 103 elements, there are approximately1000 isotopes, most of which areradioactive. 2 Figure 24-4 gives the nuclearcompositon of various isotopes.alpha particle or a beta particle . One ormore gamma rays may also be emitted withthe alpha or beta particle.An alpha particle (symbol a) is composedof two protons and two neutrons. It is thenucleus of a helium (2He^) atom, has an electricalcharge of +2, and is very stable. Inthe decay process to a more stable element,ElementRADIOACTIVITYAll isotopes with atomic number Z greaterthan 83 are naturally radioactive and many moreisotopes can be made artifically radioactive bybombarding with neutrons which upset theneutron-proton ratio of the normally stablenucleus.Naturally radioactive isotopes undergo radioactivedecomposition ,thereby forming lighterand more stable nuclei. Radioactive decompositionoccurs through the emission of an^For a detailed discussion of nuclear stability, seeFrancis W. Sears and Mark W. Zemansky, UniversityPhysios (3d ed.; Reading, Mass.: Addison-WesleyPublishing Company, Inc., 1964), p. 997.