Unit 4:Physics

Science 10

Name: Block:

Book 3: radioactivty

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5.1 : Radioactivity & Nuclear Equations

Isotopes

_______________ are versions of an element with the same

______________________ but _________________________

Because the number of protons is the same for _________________________________,

it is the number of ______________ that determines the ________ of the isotope

Isotopes are commonly named by their ___________ and _____________________

Example: carbon-14 is an isotope

of _____________ with a mass

of _____. So, it has ______

protons and

________________ neutrons.

Standard Atomic Notation

Standard atomic notation (SAN) is how we represent different isotopes in nuclear reactions:

Practice: Write the following isotopes in standard atomic notation.

potassium-39 potassium-41

23892

U

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Subatomic Particles

Nuclear reactions also commonly include subatomic particles (______________________)

which can be shown in SAN.

Practice: Write the following subatomic particles in standard atomic notation.

neutron electron proton

How are Nuclear Reactions Different from Chemical Reactions?

Chemical reactions must obey the _________________________________________

Nuclear reactions ____________________ the law of conservation of mass because atomic

nuclei can _______ or _________ subatomic particles, including _______________ and

_____________, and become other _____________/______________ as a result

Nuclear reactions can also cause the transformation of tiny amounts of mass into __________

(usually heat), according to the famous equation:

energy = _____________________________

or, E = _______

The mass lost in this way is __________________ than a single subatomic particle, so the

total number of protons and neutrons _________________________

Nuclear Equations

The ___________ radioactive isotope that ____________ in a nuclear reaction is called the

_______________________, think of it like the ______________ in a chemical reaction

The ____________ isotope that ____________ from radioactive decay in a nuclear

reaction is called the _______________________, the _________ in a chemical reaction

Like chemical reactions, we can show the radioactive decay in nuclear reactions with nuclear

equations:

13153 I → 13154 Xe + 0−1β

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Rules for Completing Nuclear Reactions

We need to obey the following rules when completing nuclear equations:

1. The sum of the ____________________ cannot change: the total atomic mass in the parent

and daughter isotopes, and decay products must be equal.

2. The sum of the ____________________ cannot change: the total number of protons in the

parent and daughter isotopes, and decay products must be equal.

Alpha Particles

Radiation created when an unstable atom decays and releases a _____________________

is called an ____________________

Alpha particles are made up of _______________ and ________________, so they have a

___________________

Because they have 2 protons and _______ electrons, alpha particles have a ______ charge

We represent alpha particles with the Greek lower case letter alpha (_______) or ______ in

SAN:

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Example: Write an equation for the alpha decay of

uranium-238.

Beta Particles

Radiation created when a _______________ in an unstable atom decays and releases an

____________ is called a ____________________

The neutron is really converted into a ____________ and an ______________

The proton remains inside the _____________ and the electron is ____________

Because they are electrons, beta particles have ____ mass and a ______ charge

We represent beta particles with the Greek lower case letter beta (______) or ______ in

SAN:

Example: Write an equation for the beta decay of

mercury-201.

STEPS:

1. Write the parent isotope in SAN2. Put an arrow after the parent isotope3. Complete the daughter isotope as follows:

decrease the atomic number of theparent isotope by 2 and the decrease theatomic mass by 4. Then, find the newelement that you have created on theperiodic table (based on the atomicnumber), and add the symbol.

4. For the other product, add an alpha particlein SAN

5. Make sure that atomic masses and atomicnumbers are balanced.

STEPS:

1. Write the parent isotope in SAN2. Put an arrow after the parent isotope3. Complete the daughter isotope as follows:

increase the atomic number of theparent isotope by 1. Leave the massnumber unchanged. Then, find the newelement that you have created on theperiodic table (based on the atomicnumber), and add the symbol.

4. For the other product, add a beta particle inSAN

5. Make sure that atomic masses and atomicnumbers are balanced.

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Gamma Rays

Radiation created when an unstable atom releases __________________ as ___________

_____________________ is called _________________________

Atoms that release gamma rays do not give off ____________ or _____________, so the

________________________________________

Because they are a form of light, gamma radiation has an

________________________________________

(far smaller than we can measure in atomic mass)

We represent gamma radiation with the Greek lower case

letter gamma (______) in SAN:

Example: Write an equation for the gamma decay

of potassium-42.

Summary

Alpha Beta Gamma

Symbol

Description

Mass

Charge

Penetration

Look at your Data Page:

STEPS:

1. Write the parent isotope in SAN. Use anasterisk to denote that it is high energy.

2. Put an arrow after the parent isotope3. Complete the daughter isotope as follows:

keep it the same as the parent isotope(but no asterisk).

4. For the other product, add a gammaparticle in SAN

5. Make sure that atomic masses and atomicnumbers are balanced.

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Part 1 – Complete the table below.

Isotope Name Atomic Number Mass Number Number of

Protons Number of Neutrons

carbon-14

carbon-15

14 15

8 16

lithium-7

24 12

14 26

11 13

neon-22

19 40

Part 2 – Write each of the following isotopes in standard atomic notation.

Isotope Standard Atomic Notation Isotope Standard Atomic

Notation

helium-3 carbon-16

potassium-40 radium-226

chlorine-36 iodine-131

sodium-23 cobalt-52

Assignment #5.1: Complete the following worksheet in the space provided below

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Part 3 – Identify the following nuclear decay reactions as either alpha decay (AD), beta decay (BD), gamma decay (GD):

Reaction Decay Type

1. 22589 Ac → 22187 Fr + 42 α

2. 14662 Sm → 14663 Eu + 0−1𝛽𝛽

3. 23191 Pa → 22789 Ac + 42He

4. 6028Ni∗ → 00 𝛾𝛾 + 6028Ni

5. 209 F → _______ + 2010Ne

6. 5826Fe∗ → 5826Fe + _______

7. 2411Na → _______ + 209 F

Part 4 – Complete the following alpha decay reactions.

Reaction

8. 20884 Po → + 4

2 α

9. 21187 Fr → + 207

85 At

10. → 22187 Fr + 42 α

Part 5 – Complete the following beta decay reactions.

Reaction

11. → 5227Co + 0−1𝛽𝛽

12. 146 C → + 0

−1𝛽𝛽

13. 13153 I → 0−1 e +

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Part 6 – Complete the following gamma decay reactions.

Reaction

14. 14964 Gd∗ → + 0

0 γ

15. → 25498 Cf + 00 γ

16. 2412Mg∗ → + 0

0 γ

Part 7 – Complete the following decay reactions.

Reaction

17. 23191 Pa → + 4

2He

18. → 15266 Dy + 00 γ

19. 22688 Ra → + 4

2 α

20. 21684 Po → + 0

−1 𝛽𝛽

21. 4018Ar∗ → + 0

0 γ

22. → 23490 Th + 42He

23. → 0−1 e + 21282 Pb

24. → 0−1 𝛽𝛽 + 20181 Tl

25. 21483 Bi → + 4

2He

26. → 23491 Pa + 00 γ

27. → 2412Mg + 0−1 e

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Half-Life

The amount of time it takes for _______ of the radioactive nuclei in a sample to __________

is called its ____________________

Some isotopes decay at a ______ rate and have ______ half-lives

Example: U-238 = 4.5 billion years!)

Others decay at a _______ rate and have __________ half-lives

Example: Astatine-213 =125 nanoseconds)

Graphing Radioactive Decay

Half-lives Amount

Remaining

0

1

2

3

4

5 0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5

Am

oun

t re

mai

nin

g (%

)

Half-lives

5.2 : Half-life & Radioactive Dating

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Radioactive Dating: carbon-14

Living organisms contain ___________ amounts of carbon-14

When they die, the carbon-14 begins to ________ into _________________ with a

half-life of _________________

By analyzing how much carbon-14 remains in a sample ____________ to how much

carbon-12, you can accurately date the

organism’s ____________

After ______________ years so little

carbon-14 remains that dating becomes

______________

Radioactive Dating: potassium-40 Clock

When __________________ cools it contains a certain amount of radioactive

________________

Over time the potassium-40 _________ into ______________, with a half-life of

__________________________

The formation of these rocks can be

dated by sampling the _________ of

the two isotopes

Other isotope pairs allow us to

accurately date rocks that are

____________ or _______

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Solving Half-Life Problems

Half-life problems involve three variables:

1. _____________________________ of the parent isotope (0, 1, 2, etc.)

2. ___________ elapsed (hours, days, years)

3. __________ of the parent isotope remaining (g, kg, or %)

A half-life problem will identify _____ of the three, you

will need to calculate the third

Make sure that you ALWAYS ____________ for half-

life and time, and at ______ for the amount of the

parent isotope

Practice: If 50 grams of carbon-14 were present in a sample of bone, state how many grams would be

left after 17 190 years?

Half-Life Time Amount

0 0 100%

Half-life Time (years) Mass (g)

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Part 1 – Complete the following tables.

Half-life Percent of

parent isotope

Percent of daughter isotope

0

1

2

3

4

Part 2 – Half-Life Word Problems

1. A rock sample contains 120 g of a radioactive isotope. The radioactive isotope has a half-life of 5years. Complete the following table.

How many years have passed if there is only 7.5 g of the parent isotope left?

2. A 36 g sample of a radioactive isotope decayed to 4.5 g in 36 minutes. How much of the originalparent isotope would remain after the first 12 minutes?

Half-life Fraction of

parent isotope

Fraction of daughter isotope

0

1

2

3

4

Half-life Time (years) Mass (g) 0 0

1 5

2 10

3 15

4 20

5 25

Assignment #5.2: Complete the following worksheet in the space provided below

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3. The half-life of a particular radioactive isotope is 8 hours. What percent of the parent isotope wouldremain after 1 day?

4. A radioactive isotope sample has a half-life of 4 days. If 6 g of the sample remains unchanged after12 days, what was the initial mass of the sample?

5. A rock sample was dated using potassium-40. Measurement indicates that 1/8 of the original parentisotope is left in the rock sample. How old is the rock sample?

6. When a sample of lava solidified, it contained 28 g of uranium-238. If that lava sample was laterfound to contain only 7 g of U-238, how many years had passed since the lava solidified?

7. After 25 years, the number of radioactive cobalt atoms in a sample is reduced to 1/32 of the originalcount. What is the half-life of this isotope?

8. The half-life of Sr-90 is 28 years. If 80 g of Sr-90 is currently in a sample of soil, how much Sr-90will be present in the soil 84 years later?

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Fission:

The ______________ of a ______________________________________ into

____________________, ________________________, and ______________ is

called ______________

The two daughter isotopes of fission reactions are

usually __________, _______________ isotopes,

leading to other decay reactions

Fission equations have a __________________ and

a ____________ which triggers the decay in the

reactants, and ____________________________

in the products

Fusion

The _______________________ of ____________________

making a ___________ _________________ and

____________ is called ___________

The ___________ daughter isotope of fusion reactions is usually a

__________ isotope

Fusion equations have __________________ in the reactants, and a ________ element

plus ____________ in the products

Fusion reactions occur ______________ in the enormous _______ and _____________

inside of _________, beginning with the fusion of hydrogen atoms together to make helium

Completing Fission/Fusion Reactions

1. Total up the __________________ and _______________________ on _______

sides of the equation

2. The _______________ in the atomic numbers _______________ the unknown product,

look it up on the periodic table and write it in SAN

3. The difference in the ____________________ gives you the _____ of the unknown product

4. Rewrite finished equation and ___________ the number of particles emitted if necessary

5.3 : Nuclear Reactions

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Practice:

The Benefits of Using Nuclear Reactions

Fission reactions are used around the world inside of ____________________________,

generating _____________ without combustion or CO2, and radioactive ‘waste’ that is useful

in medicine for creating ____________ of internal organs

Fusion power plants exist but they currently require ________________ to run _________

_______________________

The Costs of Using Nuclear Reactions

Normal operation of fission power plants does not release radioactivity, but when they fail

__________________ can be released into the environment

Fission plants create ‘waste’ daughter isotopes that are also _______________ and must be

safely ____________ to avoid ___________________ the environment

Half-lives of these radioactive waste isotopes are ________________________________,

meaning that we will be dealing with them for many ________________

Fusion reactions result in _________ daughter isotopes (we would combine hydrogen to

make helium) which have _____ environmental effects; fusion technology would greatly

___________ the impact of generating electricity

Complete the following nuclear fission reaction: 10n + 23592 U → _____ + 9442Mo + 3 10n

Complete the following nuclear fusion reaction: 21H + 31H → _____ + 10n

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The Chernobyl Disaster

A catastrophic nuclear accident occurred in _________

in the _______________

A sudden surge of power caused a nuclear power plant to

__________ and burst into flames

____________ amounts of radiation were released

This caused many devastating ___________ and ______-

term effects, including ___________________ and

___________________

Currently, Chernobyl is ___________________, and is

not expected to be habitable for ______________ years.

Summary

Fission Fusion

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Identify each of the following nuclear reactions as either fission (FI), or fusion (FU), and then complete the reaction.

Reaction Reaction Type

1. 10n + 23592 U → __________+ 12 10n + 13654 Xe

2. 31H + 21H → 10n + __________

3. 23592 U + 10n → 14156 Ba + ______ 10n + 9236Ba

4. 10n + __________ → 6 10n + 14355 Cs + 9037Rb

5. 10n + 23592 U → 14354 Xe + 3 10n + __________

6. 21H + 21H → 10n + __________

7. 10n + 23592 U → __________ + 4 10n + 8032Ge

8. 21H + 63 Li → + __________ + 10n

9. __________ + 10n → 14054 Xe + 4 10n + 11346 Pd

10. 10n + 23592 U → 3 10n + __________ + 12753 I

11. 21H + 31H → __________+ 42He

12. 10n + 23592 U → 3 10n + 11549 In + __________

13. __________+ 10n → 13752 Te + 3 10n + 10042 Mo

14. 10n + 3517Cl → __________ + 21H

Assignment #5.3: Complete the following worksheet in the space provided below

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Vocabulary: Referring to your notes and textbook, define each of the following vocabulary terms in a complete sentence:

1. Alpha Particle

2. Beta Particle

3. Daughter Isotope

4. Fission

5. Fusion

6. Gamma Radiation

7. Half-Life

8. Isotope

9. Parent Isotope

Physics (Part 2) Unit Review Package

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Knowledge:

Write the following isotopes in standard atomic notation.

10. cobalt-60 11. barium-133 12. sodium-22

13. zinc-65 14. americium-241 15. hydrogen-3

16. Complete the following table describing the three types of radiation:

Alpha Beta Gamma

Symbol

Description

Mass

Charge

Identify each of the following nuclear reactions as alpha decay (AD), beta decay (BD), gamma decay (GD), fission (FI), or fusion (FU).

17. 20180

Hg → 20181

Tl + 0−1

β ____________

18. 10n + 235

92U → 139

50Tn + 94

42Mo + 3 1

0n

____________

19. 22589

Ac → 22187

Fr + 42α

____________

20. 23191

Pa → 42He + 227

89Ac

____________

21. 2411Na → 0

−1e + 24

12Mg

____________

22. 6028Ni* → 60

28Ni + 0

0γ

____________

23. 10n + 235

92U → 92

36Kr + 3 1

0n + 141

56Ba

____________

24. 21H + 6

3Li → 7

4Be + 1

0n

____________

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25. What are some important differences between chemical reactions and nuclear reactions?

Complete the following nuclear reactions. Be sure to show your work in the space provided.

26. 23892

U + 42He

_____________________________________________________________________

27. 2411Na + 0

−1e

_____________________________________________________________________

28. 10n + 235

92U → + 3 1

0n + 77

34Se

_____________________________________________________________________

29. 4019K + 0

−1β

_____________________________________________________________________

30. 32He + 0

0𝛾

_____________________________________________________________________

31. 42He + 28

12Mg

_____________________________________________________________________

32. 4621Sc + 4

2α

_____________________________________________________________________

33. 10n + 235

92U → 93

40Zr + + 3 1

0n

_____________________________________________________________________

34. 10n + 235

92U → + 3 1

0n + 105

46Pd

_____________________________________________________________________

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35. Describe the disadvantages and advantages of using fission reactions to generate electricity.

36. At right is the decay curve for potassium-40 and itsdaughter isotope argon-40. You analyse a sample ofvolcanic rock and find 10% potassium-40 compared to90% argon-40. How long ago were these rocks formed?Explain your answer.

37. If a rock originally contains 100 g of a radioactiveisotope, how much will be left after 3 half-lives? Show your work.

38. A bone contains 20g of a radioactive isotope that has a half-life of 1000 years. How much will beleft after 2000 years? Show your work.

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39. If a rock has only 20 g of radioactive isotope remaining after 3 half-lives, how much was there tostart with? Show your work.

40. Carbon-14 has a half-life of 5730 years. How much of an original sample weighing 80 g would beleft after 22,920 years? Show your work.

41. You weigh a sample of unknown radioactive material and find that it weighs 50 kg. If the sampleoriginally weighed 200 kg, and is now 2.6 billion years old, identify its half-life and the parentisotope. Show your work.

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