Chapter Questions
What is the energy emitted when anucleus forms?
What is a nucleon?
What is the high-energy electromagneticradiation produced by decaying nuclei?
What nuclear reaction happens when twosmall nuclei combine?
Explain the difference between fissionand fusion.
Name the process that describes an unstablenucleus that emits particles and energy.
Define critical mass.
Define half-life.
What is the combination of neutrons andprotons in a nucleus known as?
Name two types of nuclear changes.
Explain how the strong force holds anucleus together despite the repulsive forcesbetween protons.
Describe what happens to unstable nuclei.
A. What is the relationship among the number of protons, the number of neutrons, and the stability of the nucleus for small atoms?B. What is the relationship among number of protons, the number of neutrons, and the stability of the nucleus for large atoms?
What is the relationship between bindingenergy and the formation of a nucleus fromprotons and neutrons?
What is the relationship between massdefect and binding energy?
Why is nuclear stability better indicated bybinding energy per nucleon than by totalbinding energy per nucleus?
What is a quark?
What is the relationship between an alphaparticle and a helium nucleus?
Compare the penetrating powers of alphaparticles, beta particles, and gamma rays.
Is the decay of an unstable isotope into astable isotope always a one-step process?Explain.
a. What role does a neutron serve in startinga nuclear chain reaction and in keepingit going?b. Why must neutrons in a chain reactionbe controlled?c. Why must there be a minimum mass ofmaterial in order to sustain a chain reaction?
Under what conditions does fusion occur?
Why do positron emission and electroncapture have the same effect on a nucleus?
Explain why nuclei that emit alpha particles,such as americium-241, are safe to use insmoke detectors.
How does acute radiation exposure differfrom chronic radiation exposure?
Why do animals contain the same ratio ofcarbon-14 to carbon-12 as plants do?
What type of radioactive nuclide is injectedinto a person who is about to undergo aPET scan?
Describe how nuclear chemistry can beused to detect an art forgery.
What does the unit rem describe?
The decay of uranium-238 results in thespontaneous ejection of an alpha particle.Write the nuclear equation that describesthis process.
What type of radiation is emitted in thedecay described by the following equation?$$_{19}^{43} \mathrm{K} \rightarrow_{20}^{43} \mathrm{Ca}+?$$
When a radon-222 nucleus decays, an alpha particle is emitted. Write the nuclear equation to show what happens when a radon-222 nucleus decays. What is the other product that forms?
One radioactive decay series that begins withuranium-235 and ends with lead-207 showsthe partial sequence of emissions: alpha,beta, alpha, beta, alpha, alpha, alpha, alpha,beta, beta, and alpha. Write an equation foreach reaction in the series.
Balance the following nuclear reactions.\begin{equation}a. \quad_{93}^{239} \mathrm{Np} \longrightarrow_{-1}^{0} e+?\end{equation}\begin{equation}\begin{array}{l}{\text { b. }_{4}^{9} \mathrm{Be}+_{2}^{4} \mathrm{He} \longrightarrow ?} \\ {\text { c. } _{15}^{32} \mathrm{P}+? \longrightarrow_{15}^{33} \mathrm{P}}\end{array}\end{equation}\begin{equation}d. _{92}^{236} \mathrm{U} \longrightarrow_{36}^{94} \mathrm{Kr}+?+3_{0}^{1} n\end{equation}
Complete and balance the following nuclearequations:\begin{equation}a. \quad_{75}^{187} \mathrm{Re}+? \longrightarrow_{75}^{188} \mathrm{Re}+_{1}^{1} \mathrm{H}\end{equation}\begin{equation}b.\quad_{4}^{9} \mathrm{Be}+_{2}^{4} \mathrm{He} \longrightarrow ?+_{0}^{1} n\end{equation}\begin{equation}c.\quad_{11}^{22} \mathrm{Na}+? \longrightarrow_{10}^{22} \mathrm{Ne}\end{equation}
Write the nuclear equation for the releaseof a positron by $_{54}^{117} \mathrm{Xe} .$
Copper-64 is used to study brain tumors.Assume that the original mass of a sampleof copper-64 is 26.00 g. After 64 hours, allthat remains is 0.8125 g of copper-64. Whatis the half-life of this radioactive isotope?
The half-life of thorium-234 is 24.10 days.How many days until only one-sixteenth ofa 52.0 g sample of thorium-234 remains?
The half-life of carbon-14 is 5715 y. How long will it be until only half of the carbon-14 in a sample remains?
The half-life of one radon isotope is 3.8days. If a sample of gas contains 4.38 g ofradon-222, how much radon will remain inthe sample after 15.2 days?
After 4797 y, how much of an original0.450 g of radium-226 remains? The half-lifeof radium-226 is 1599 y.
The half-life of cobalt--60 is 10.47 min. Howmany milligrams of $\mathrm{Co}-60$ remain after104.7 min if you start with 10.0 $\mathrm{mg}$ of $\mathrm{Co}-60$ ?
Calculate the neutron-proton ratios for thefollowing nuclides, and determine wherethey lie in relation to the band of stability.\begin{equation}a. _{92}^{235} \mathrm{U}\end{equation}\begin{equation}b. _{8}^{16} \mathrm{O}\end{equation}\begin{equation}c. _{26}^{56} \mathrm{Fe}\end{equation}\begin{equation}c. _{60}^{156} \mathrm{Nd}\end{equation}
Calculate the binding energy per nucleonof $_{92}^{238} \mathrm{U}$ in joules. The atomic mass of a $_{92}^{238} \mathrm{U}$nucleus is 238.050784 amu.
The energy released by the formation of a nucleus of $_{26}^{56} \mathrm{U}$ is $7.89 \times 10^{-11} \mathrm{J}$ Einstein's equation, $E=m c^{2},$ to determine how much mass is lost (in kilograms) in this process.
What nuclear process is occuring in the sunshown? Also, write a nuclear reaction thatdescribes this process.
The radiation given off by iodine-131 in the form of beta particles is used to treat cancer of the thyroid gland.Write the nuclear equation to describe the decay of an iodine-131 nucleus.
The parent nuclide of the thorium decayseries is $_{90}^{232}$ Th. The first four decays are asfollows: alpha emission, beta emission, betaemission, and alpha emission. Write thenuclear equations for this series of emissions.
The half-life of radium- $-224$ is 3.66 days.What was the original mass of radium-224if 0.0500 g remains after 7.32 days?
How many milligrams remain of a 15.0 $\mathrm{mg}$sample of radium-226 after 6396 $\mathrm{y} ?$ Thehalf-life of this isotope is 1599 $\mathrm{y}$ .
The mass of a $_{3}^{7}$ Li atom is 7.01600 amu.Calculate its mass defect.
Determine whether each of the followingnuclear reactions involves alpha decay, betadecay, positron emission, or electroncapture.\begin{equation}\begin{array}{l}{\text { a. }_{90}^{234} \mathrm{Th} \rightarrow_{-1}^{0} e+_{91}^{234} \mathrm{Pa}} \\ {\text { b. }_{92}^{238} \mathrm{U} \longrightarrow_{2}^{4} \mathrm{He}+_{90}^{234} \mathrm{Th}} \\ {\text { c. }_{8}^{15} \mathrm{O} \longrightarrow_{+1}^{0} e+_{7}^{15} \mathrm{N}}\end{array}\end{equation}
Uranium-238 decays through alpha decaywith a half-life of $4.46 \times 10^{9}$ y. How longwould it take for seven-eighths of a sampleof uranium- $-238$ to decay?.
Write the nuclear equation for the releaseof an alpha particle by $_{70}^{157} \mathrm{Yb} .$
The half-life of iodine- $-131$ is 8.02 days. Whatpercentage of an iodine-131 sample willremain after 40.2 days?
The mass of a $_{10}^{20} \mathrm{Ne}$ atom is 19.99244 amu.Calculate its mass defect.
Calculate the nuclear binding energy of onelithium-6 atom. The measured atomic massof lithium-6 is 6.015 amu.
Write the nuclear equation for the releaseof a beta particle by $_{210}^{82} \mathrm{Pb} .$
The half-life of an element $X$ is 5.25 y. Howmany days are required for one-fourth of agiven amount of $X$ to decay?
Complete the following nuclear reactions.\begin{equation}a. _{5}^{12} \mathrm{B} \rightarrow_{6}^{12} \mathrm{C}+?\end{equation}\begin{equation}b. _{89}^{225} \mathrm{Ac} \longrightarrow_{87}^{221} \mathrm{Fr}+?\end{equation}\begin{equation}\mathbf{c.}_{28}^{63} \mathrm{Ni} \longrightarrow ?+_{-1}^{0} e\end{equation}\begin{equation}\mathbf{d} \cdot_{83}^{212} \mathrm{Bi} \rightarrow ?+_{2}^{4} \mathrm{He}\end{equation}
Actinium-217 decays by releasing an alphaparticle. Write an equation for this decayprocess, and determine what element isformed.
Indicate if the following equations representfission reactions or fusion reactions.\begin{equation}a. _{1}^{1} \mathrm{H}+_{1}^{2} \mathrm{H} \longrightarrow_{2}^{3} \mathrm{He}+\gamma\end{equation}\begin{equation}b. _{0}^{1} n+_{92}^{235} \mathrm{U} \longrightarrow_{57}^{146} \mathrm{La}+_{35}^{87} \mathrm{Br}+3_{0}^{1} n\end{equation}\begin{equation}c. _{10}^{21} \mathrm{Ne}+_{2}^{4} \mathrm{He} \longrightarrow_{12}^{24} \mathrm{Mg}+_{0}^{1} n\end{equation}\begin{equation}d. _{82}^{208} \mathrm{Pb}+_{58}^{26} \mathrm{Fe} \longrightarrow_{108}^{265} \mathrm{Hs}+_{0}^{1} n\end{equation}
Predict whether the total mass of the 26protons and neutrons that make up the ironnucleus will be more, less, or equal to 55.845amu, the mass of an iron atom from theperiodic table. If it is not equal, explainwhy not.
A sample of francium- 212 will decay to one sixteenth its original amount after $80 \mathrm{~min}$. What is the half-life of francium-212?
Identify which of the four common types ofnuclear radiation (beta, neutron, alpha, orgamma) correspond to the followingdescriptions:\begin{equation}\begin{array}{l}{\text { a. an electron }} \\ {\text { b. uncharged particle }} \\ {\text { c. can be stopped by a piece of paper }} \\ {\text { d. high-energy light }}\end{array}\end{equation}
Calculate the time required for three-fourths of a sample of cesium-138 to decaygiven that its half-life is 32.2 $\mathrm{min} .$
Calculate that half-life of cesium-135 ifseven-eighths of a sample decays in $6 \times 10^{6} \mathrm{y}$ .
An archaeologist discovers a wooden maskwhose carbon-14 to carbon-12 ratio is one-sixteenth the ratio measured in a newlyfallen tree. How old does the wooden maskseem to be, given this evidence?
The half-life of tritium, $_{1}^{3} \mathrm{H},$ is 12.3 $\mathrm{y} .$ Howlong will it take for seven-eighths of thesample to decay?
It takes about $10^{6}$ y for just half the samar-ium-149 in nature to decay by alpha-particleemission. Write the decay equation, and findthe isotope that is produced by the reaction.
Describe some of the similarities and differ-ences between atomic electrons and betaparticles.
Medium-mass nuclei have larger bindingenergies per nucleon than heavier nuclei do.What can you conclude from this fact?
Why are elevated temperatures necessaryto initiate fusion reactions but not fissionreactions?
Why is the constant rate of decay of radioac-tive nuclei so important in radioactive dating?
Why would someone working around radio-active waste in a landfill use a radiation
monitor instead of a watch to determinewhen the workday is over? At what pointwould that person decide to stop working?
Explain why charged particles do not pene-trate matter deeply.
Research some important historical findingsthat have been validated through radioactivedating. Report your findings to the class.
Design an experiment that illustrates theconcept of half-life.
Research and evaluate environmental issuesregarding the storage, containment, anddisposal of nuclear wastes.
Suppose you are an energy consultant whohas been asked to evaluate a proposal tobuild a power plant in a remote area of thedesert. Research the requirements for eachof the following types of power plant:nuclear-fission power plant, coal-burningpower plant, solar-energy farm. Decidewhich of these power plants would be bestfor its surroundings, and write a paragraphsupporting your decision.
Use the following terms to complete theconcept map below: critical mass, chainreaction, nuclear fission, and nucleon.
Study the graph below, and answer the questions that follow.For help in interpreting graphs, see Appendix B, "Study Skills for Chemistry."Do stable nuclei that have N/Z numbersapproximately equal to 1 have small orlarge atomic numbers?
Study the graph below, and answer the questions that follow.For help in interpreting graphs, see Appendix $B$ , "Study Skills for Chemistry."Do stable nuclei that have $N / Z$ numbersapproximately equal to 1.5 have small orlarge atomic numbers?
Study the graph below, and answer the questions that follow.For help in interpreting graphs, see Appendix $B,$ "Study Skills for Chemistry."Calculate the $N / Z$ number for a nucleus $\mathrm{A}$that has 70 neutrons and 50 protons.
Study the graph below, and answer the questions that follow.For help in interpreting graphs, see Appendix $B,$ "Study Skills for Chemistry."Calculate the $N / Z$ number for a nucleus $\mathrm{B}$that has 90 neutrons and 60 protons.
Study the graph below, and answer the questions that follow.For help in interpreting graphs, see Appendix $B,$ "Study Skills for Chemistry."Does nucleus A or nucleus B have an $N / Z$number closer to 1.5$?$
Calculating the Amount of Radioactive Material The graphing calculator can run a program that graphs the relationship between the amount of radioactive material and elapsed time. Given the half-life of the radioactive material and the initial amount of material in grams, you will graph the relationship between the amount of radioactive material and the elapsed time. Then, with the elapsed time, you will trace the graph to calculate the amount of radioactive material.Go to Appendix C. If you are using a TI-83Plus, you can download the program RADIOACT and run the application as directed. If you are using another calculator, your teacher will provide you with key-strokes and data sets to use. After you have run the program, answer these questions.a. Determine the amount of neptunium-235 left after 2.0 years, given the half-life of neptunium-235 is 1.08 years and the initial amount was 8.00 g.b. Determine the amount of neptunium-235 left after 5.0 years, given the half-life of neptunium-235 is 1.08 years and the initial amount was 8.00 g.c. Determine the amount of uranium-232 left after 100 years, given the half-life of uranium-232 is 69 years and the initial amount was 10.0 g.