Quantum Physics

956 Chapter 29 Nuclear Physicsbombarding particles. He found that protons were released when alpha particleswere allowed to collide with nitrogen atoms. The process can be representedsymbolically as42 He 14 7N : X 1 1 H[29.20]This equation says that an alpha particle ( 4 2 He) strikes a nitrogen nucleus and producesan unknown product nucleus (X) and a proton ( 1 1 H) . Balancing atomicnumbers and mass numbers, as we did for radioactive decay, enables us to concludethat the unknown is characterized as 8 X. Because the element with atomic17number 8 is oxygen, we see that the reaction is42 He 14 7 N : 17 8 O 1 1H[29.21]This nuclear reaction starts with two stable isotopes—helium and nitrogen—andproduces two different stable isotopes—hydrogen and oxygen.Since the time of Rutherford, thousands of nuclear reactions have been observed,particularly following the development of charged-particle accelerators inthe 1930s. With today’s advanced technology in particle accelerators and particledetectors, it is possible to achieve particle energies of at least 1 000 GeV 1TeV.These high-energy particles are used to create new particles whose properties arehelping to solve the mysteries of the nucleus (and indeed, of the Universe itself).Quick Quiz 29.4Which of the following are possible reactions?1(a) 0n 23592U : 14054Xe 9438Sr 2( 1 0n)1(b) 0n 23592U : 132 10150Sn 42 Mo 3(1 0 n)(c) 1 0n 23994Pu : 12753I 93 41Nb 3( 1 0 n)EXAMPLE 29.8GoalThe Discovery of the NeutronBalance a nuclear reaction to determine an unknown decay product.Problem A nuclear reaction of significant note occurred in 1932 when Chadwick, in England, bombarded aberyllium target with alpha particles. Analysis of the experiment indicated that the following reaction occurred:What isAZXin this reaction?42He 9 4Be : 12 6C A Z XStrategyBalancing mass numbers and atomic numbers yields the answer.SolutionWrite an equation relating the atomic masses on either side:4 9 12 A : A 1Write an equation relating the atomic numbers: 2 4 6 Z : Z 0Identify the particle:AZX 10 n (a neutron)RemarksThis experiment was the first to provide positive proof of the existence of neutrons.Exercise 29.8Identify the unknown particle in this reaction:42 He 14 7 N : 17 8 O A Z XAnswerAZ X 1 1 H(a neutral hydrogen atom)