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21 Nuclear Chemistry Solutions to Exercises Radioactive: Cu -odd proton, odd neutron, low neutron/proton ratio high atomic number Stable: 28 Ni - even proton, even neutron, stable neutron/proton ratio stable neutron/proton ratio, (one of 5 stable odd proton/odd neutron nuclides) even proton, even neutron, stable neutron/proton ratio Nuclear Transmutations (section 21.3) 21.25 Protons and alpha particles are positively charged and must be moving very fast to overcome electrostatic forces which would repel them from the target nucleus. Neutrons are electrically neutral and not repelled by the nucleus. 21.26 The element is technetium, Tc. 21.27 Analyze/Plan. Determine A and Z for the missing particle by conservation principles. Find the appropriate symbol for the particle. Solve. (a) (b) + (c) 3 (d) 1321 (e) 21.28 (a) (b) + (orbital electron) (c) (d) + Co (e) 21.29 Analyze/Plan. Follow the logic in Sample Exercise 21.5, paying attention to conservation of A and Z. Solve. (a) (b) (c) 21.30 (a) (b) + (c) Rates of Radioactive Decay (section 21.4) 21.31 (a) True. k = The decay rate constant, k, and half-life, t1/2 are inversely related. (b) False. If X is not radioactive, it does not spontaneously decay and its half-life is essentially infinity. 652