Nuclear Chemistry Name____________________

Chapter 28 Assignment & Problem Set

Warm-Ups (Show your work for credit)

Date______________ 1. Date______________ 2.

Answer: Answer:

Date______________ 3. Date______________ 4.

Answer: Answer:

Date______________ 5. Date______________ 6.

Answer: Answer:

Date______________ 7. Date______________ 8.

Answer: Answer:

Nuclear Chemistry 2

Chapter 28 Assignment & Problem Set

Study Guide: Things You Must Know

Vocabulary (know the definition and what it means):

nuclear chemistry

isotope

isotope notation

mass number

atomic number

beta radiation

alpha radiation

gamma radiation

elementary particle

proton

neutron

electron

positron

alpha

natural transmutation

artificial transmutation

radioisotope (nuclide)

nuclear stability

belt of stability

beta emission

positron emission

Honors: electron capture

alpha emission

parent and daughter nucleus

half-life

half-life period

radioactive dating

radioactive tracer

fission and fusion

nuclear chain reaction

Geiger counter

scintillation counter

Learning Objectives:

what subatomic particles are in the nucleus

how to write isotope notation showing the atomic number and mass number

how to interpret the symbols and notations of particles using Table O

how to determine the numbers of protons and neutrons in the nucleus given the notation of an isotope

what types of radiation are emitted by a nucleus undergoing natural transmutation

what types of nuclear radiation are most/least damaging to human tissue

how to balance nuclear reactions and predict missing particles in nuclear reactions

how to interpret the belt of stability

how to predict the type of radiation emitted using belt of stability rules using atomic mass on the Periodic

Table as a guide

how to write balanced nuclear equations using Table N

how to solve numerical problems involving half-life

how artificial transmutation differs from natural transmutation

uses of radioisotopes: carbon dating, medical applications, power generation, nuclear weapons

the similarities and differences between nuclear fission and nuclear fusion

how nuclear radiation is detected

the essential differences between chemical reactions and nuclear reactions

Reference Tables you should know how to interpret:

Table N: Selected Radioisotopes

Table O: Symbols Used in Nuclear Chemistry

Nuclear Chemistry 3

Chapter 28 Assignment & Problem Set •Read Chapter 28

•Lab 28: Understanding Half-Life

•Regents Tables

Table N: Selected Radioisotopes

Table O: Symbols Used in Nuclear Chemistry

Table T: Important Formulas and Equations

•Warm-ups and problems will be collected before you take the test. Answer all problems in the space provided.

For problems involving an equation, carry out the following steps: 1. Write the equation.

2. Substitute numbers and units. 3. Show the final answer with units. There is no credit without showing work.

Isotope Notation

1. How many protons, neutrons, and electrons are in atoms of each isotope.

protons neutrons electrons

iron-59

Fe-55

uranium-235

C-14

Th-234

Types of Radiation

2. Complete the table comparing alpha, beta, and gamma radiation.

Alpha Beta Gamma

Symbol

Mass

Charge

Damage to human

tissue

Balancing Nuclear Reactions

3. Complete and balance the equations for the following nuclear reactions.

a. Al2713 + He4

2 Si3014 + ? c. Si27

14 01 + ?

b. Bi21483 He4

2 + ? d. Cu6629 Zn66

30 + ?

4. Write an equation for the radioactive decay of fluorine-17 by positron emission.

Nuclear Chemistry 4

Chapter 28 Assignment & Problem Set 5. Write a nuclear equation for each word equation.

a. Neon-19 undergoes positron decay.

b. Kr-85 undergoes beta decay.

c. Alpha radiation is emitted during the disintegration of uranium-238.

6. Write a nuclear equation for the decay of each of the following radioisotopes.

a. Carbon-14.

b. Radon-222

c. I-131

7. What isotope remains after three beta particles and five alpha particles are lost from a thorium-234 isotope?

Belt of Stability and Predicting Nuclear Reactions

8. What is meant by the “belt of stability”?

9. What happens to an isotope that falls outside the band of stability?

10. Explain the difference between an isotope and radioisotope.

11. Identify the more stable isotope in each pair.

a. C-14, C-13 b. H-1, H-3 c. O-16, O-18 d. N-15, N-14 e. K-40, K-39

Nuclear Chemistry 5

Chapter 28 Assignment & Problem Set 12. How are mass number and atomic number of a nucleus affected by the loss of the following?

a. beta particle

b. alpha particle

c. gamma rays

13. Using the “belt of stability”, predict the mode of decay and write balanced nuclear equations for the decay of:

a. Zr-97

b. Th-230

Half-Life

14. Explain “half-life.”

15. Manganese-56 is a beta emitter with a half-life of 2.6 h. What is the mass of manganese-56 in a 1.0 mg sample

of the isotope at the end of 10.4h?

16. The mass of thorium 234 in a sample is found to have decreased from 0.800g to 0.100g in a period of 72.3

days. From this information, calculate the half-life of thorium 234.

17. A patient is administered 20 mg of iodine-131. How much of this isotope will remain in the body after 40 days?

18. For the decay of Fr-220:

a. Write a balanced nuclear equation.

b. What is the half-life?

Nuclear Chemistry 6

Chapter 28 Assignment & Problem Set

c. If you start with 72 g of Fr-220, how much is left after 1.83 minutes?

19. For the decay of Co-60, used for treating cancer, what percent of Co-60 remains after 7 half-lives?

Transmutation

20. What is the difference between natural and artificial decay?

21. Give an example nuclear equation for the synthesis of a transuranium element by artificial transmutation.

Uses of Radioactive Isotopes

22. What is a “radioactive tracer”?

23. What types of radiation can be detected using a Geiger counter? A scintillation counter?

24. Why is it important that radioactive isotopes used internally for medical diagnosis or treatment have relatively

short half-lives?

25. Explain how iodine-131 is used to treat thyroid disease.

Fission and Fusion

26. Define fission and define fusion. Which is currently used as a reliable source of energy?

27. Where does fusion occur naturally?

28. What equation is used to calculate the energy that comes from both fission and fusion? Define all terms in the

equation.

Nuclear Chemistry 7

Chapter 28 Assignment & Problem Set

29. Assuming technical problems could be overcome, what are some advantages to producing electricity in a fusion

reactor?

Review

30. Balance the following equations.

a. Ca(OH)2 + HCl CaCl2 + H2O

b. Fe2O3 + H2 Fe + H2O

c. NaHCO3 + H2SO4 Na2SO4 + CO2 + H2O

d. C2H6 + O2 CO2 + H2O

31. You have a 0.30M solution of sodium sulfate. What volume in ml must be measured to give 0.0020 mol of

sodium sulfate?

32. Identify the bonds between each pair of atoms as ionic (I) or covalent (C).

a. carbon and silicon

b. calcium and fluorine

c. sulfur and nitrogen

d. bromine and cesium

33. How many liters of hydrogen gas (at STP) will be produced when 10.00 g of magnesium metal reacts with an

excess of sulfuric acid? First write a balanced chemical equation.

Nuclear Chemistry 8

Chapter 28 Assignment & Problem Set

Using the Belt of Stability to Predict Nuclear Reactions

The best way to understand nuclear decay is determine which combinations of protons and neutrons in a nucleus

are stable. This relationship can be viewed by plotting the number of neutrons (y-axis) vs. number of protons (x-

axis) as shown in the figure below. The dark-shaded area in the figure is called the belt of stability, which

represents all combinations of protons and neutrons that lead to a stable nucleus. All other combinations of protons

and neutrons give nuclei that are not stable, called radioisotopes, that will turn into a different element accompanied

by emission of radiation.

Belt of Stability

Several generalizations can be made by looking at the plot.

1. For low atomic numbers, up to about the element calcium, stable nuclei have equal numbers of protons and

neutrons.

2. For higher atomic numbers, stable nuclei have greater numbers of neutrons than protons.

3. All elements with atomic number greater that 82 (Pb) are unstable.

Modes of Nuclear Decay

The unstable regions on the plot can be broken into three areas, A, B, and C, each with its own modes of decay.

Region A (too many neutrons leads to beta emission): This region decays by turning a neutron in the nucleus into

a proton, accompanied by the emission of a beta particle (electron).

n10 p1

1 + e01-

example of beta emission: K4019 Ca40

20 + e01-

Nuclear Chemistry 9

Chapter 28 Assignment & Problem Set Region B (too few neutrons leads to either positron emission or electron capture): This region can decay by

two different modes, positron emission or electron capture. For positron emission, a proton in the nucleus turns into

a neutron accompanied by the emission of a positron.

p11 n1

0 + e01

example of positron emission: K3819 Ar38

18 + e01

The other possible decay in region B is electron capture, where an electron orbiting the nucleus is captured by the

nucleus.

example of electron capture: Ar3718 + e0

1- Cl3717

Region C (too many protons and neutrons leads to alpha emission): Very large nuclei give off an alpha particle

in order to reduce their mass.

example of alpha emission: U23892 Th234

90 + 42

A last tip: Often you can predict the mode of decay by comparing the mass number of the nucleus to the average

atomic mass of that element found on the periodic table. For example, the isotope K-40 is more massive than the

average mass for K found on the period table (39.1 amu). Thus one could rightly guess that K-40 would decay by

beta emission (region A).

Summary: Modes of Decay

Region Isotope Compared to Periodic Table Modes of Decay

A: too many n

(above belt of stability, and

atomic numbers 1-82)

Mass number of isotope is greater

than mass on Periodic Table beta emission

B: too few n

(below belt of stability, and

atomic numbers 1-82)

Mass number of isotope is less

than mass on Periodic Table positron emission

C: too many n & p+

(past belt of stability) Atomic number greater than 82 (Pb) alpha emission