Chapter 25

Explain the important distinctions between each pair of terms: (a) electron and positron; (b) half-life and decay constant; (c) mass defect and nuclear binding energy; (d) nuclear fission and nuclear fusion; (e) primary and secondary ionization.

Which of the following types of radiation is deflected in a magnetic field? (a) \(X\) ray; (b) \(\gamma\) ray; (c) \(\beta\) ray; (d) neutrons.

A process that produces a one-unit increase in atomic number is (a) electron capture; (b) \(\beta^{-}\) emission;(c) \(\alpha\) emission; (d) \(\gamma\) -ray emission.

Of the following nuclides, the one most likely to be radioactive is \((a)^{31} P ;(b)^{66} Z n ;(c)^{35} C l ;(d)^{108} A g\).

One of the following elements has eight naturally occurring stable isotopes. We should expect that one to be (a) \(\mathrm{Ra} ;\) (b) \(\mathrm{Au} ;\) (c) \(\mathrm{Cd} ;\) (d) Br.

Of the following nuclides, the highest nuclear binding energy per nucleon is found in (a) \(_{1}^{3} \mathrm{H} ;\) (b) \(_{8}^{16} \mathrm{O} ;\) (c) \(_{26}^{56} \mathrm{Fe}\); (d) \(_{92}^{235} \mathrm{U}\).

The most radioactive of the isotopes of an element is the one with the largest value of its (a) half-life, \(t_{1 / 2}\) (b) neutron number, \(N ;\) (c) mass number, \(Z\) (d) radioactive decay constant, \(\lambda\)

Given a radioactive nuclide with \(t_{1 / 2}=1.00 \mathrm{h}\) and a current disintegration rate of 1000 atoms \(s^{-1}\), three hours from now the disintegration rate will be (a) 1000 atoms \(s^{-1} ;\) (b) 333 atoms \(s^{-1} ;\) (c) 250 atoms \(s^{-1}\); (d) 125 atoms \(s^{-1}\)

Write nuclear equations to represent (a) the decay of \(^{214} \mathrm{Ra}\) by \(\alpha\) -particle emission (b) the decay of \(^{205}\) At by positron emission (c) the decay of \(^{212} \mathrm{Fr}\) by electron capture (d) the reaction of two deuterium nuclei (deuterons) to produce a nucleus of \(\frac{3}{2} \mathrm{He}\). (e) the production of \({243}_{97} \mathrm{Bk}\) get by the \(\alpha\) -particle bombardment of\({241}_{95} \mathrm{Am}\) (f) a nuclear reaction in which thorium-232 is bombarded with \(\alpha\) particles, producing a new nuclide and four neutrons.

232 Ra has a half-life of 11.4 d. How long would it take for the radioactivity associated with a sample of \(^{232} \mathrm{Ra}\) to decrease to \(1 \%\) of its current value?

A sample of radioactive \(\frac{35}{16} \mathrm{S}\) disintegrates at a rate of \(1.00 \times 10^{3}\) atoms \(\min ^{-1} .\) The half-life of \(_{16}^{35} \mathrm{S}\) is \(87.9 \mathrm{d}\) How long will it take for the activity of this sample to decrease to the point of producing (a) \(253 ;\) (b) \(104 ;\) and (c) 52 dis \(\min ^{-1} ?\)

Neutron bombardment of \(^{23}\) Na produces an isotope that is a \(\beta\) emitter. After \(\beta\) emission, the final product is (a) \(^{24} \mathrm{Na} ;\) (b) \(^{23} \mathrm{Mg} ;\) (c) \(^{23} \mathrm{Ar} ;\) (d) \(^{24} \mathrm{Ar} ;\) (e) none of these.

A nuclide has a decay rate of \(2.00 \times 10^{10} \mathrm{s}^{-1} .\) After 25.0 days, its decay rate is \(6.25 \times 10^{8} \mathrm{s}^{-1}\). What is the nuclide's half-life? (a) 25.0 d; (b) 12.5 d; (c) 50.0 d; (d) \(5.00 \mathrm{d} ;\) (e) none of these.

A nuclide has a decay constant of \(4.28 \times 10^{-4} \mathrm{h}^{-1}\). If the activity of a sample is \(3.14 \times 10^{5} \mathrm{s}^{-1},\) how many atoms of the nuclide are present in the sample? (a) \(2.64 \times 10^{12} ;\) (b) \(7.34 \times 10^{8}\) (c) \(2.04 \times 10^{5}\) (d) \(4.40 \times 10^{10} ;\) (e) none of these.