Unit 12 Nuclear Chemistry Notes & CW · PDF fileUnit 12 - Nuclear Chemistry Notes & CW ... or...

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Unit 12 - Nuclear Chemistry Notes & CWUnit Objectives

Upon completion of the unit students should be able to: Predict the stability of an isotope based on the ratio of neutrons and protons in its nucleus.

Understand that while most nuclei are stable some are unstable and spontaneously decay

emitting radiation.

Calculate the initial amount of the fraction remaining, or the half life of a radioactive

isotope, using the half life equation.

Understand the concept of half life.

Differentiate between the following emissions based on mass, charge, ionizing power, and

penetrating power: Alpha, Beta, Positron, and Gamma

Determine the type of decay (alpha, beta, positron, and gamma) and write the nuclear

equations.

Compare and contrast fission and fusion reactions

Distinguish between natural and artificial transformations.

Complete nuclear equations and predict missing particles from nuclear equations.

Understand the change in energy in a nuclear reaction.

Be aware of the risks associated with radioactivity.

Recognize the beneficial uses and real world application of radioactive isotopes.

Radioactive dating

Tracing chemical and biological processes

Industrial measurement

Nuclear power

Detection and treatment of diseases

Focus Questions for the Unit: What determines nuclear stability?

How does an unstable element stabilize?

YOU SHOULD BE ABLE TO ANSWER THESE IN DETAIL BY THE END OF THE UNIT Define the following vocabulary:

Artificial transmutation

Atomic Mass Unit (amu)

Atomic number

Half-life Isotope

Mass number

Radioactivity (Radioactive Decay)

Nuclear charge

Nuclear fission

Nuclear fusion

Average Weighted Mass

Tracer

Name: _______________________________________

The bold, underlined words are important vocabulary words that you should be able to define and use properly in explanations. This is a study guide for what you will be tested on throughout the year. The objectives are divided into categories of “Knowledge” (what you have to know) and “Application” (what you have to be able to do).

I. NUCLEAR CHEMISTRY

Knowledge Application

1.

o The stability of an isotope is based on the ratio of the neutrons and protons in the nucleus.o Usually when the ratio is not 1:1, the nucleus gets a little unstable and starts spitting out particles so that it will

have a more stable 1:1 ratio.o Although most nuclei are stable, some are unstable and spontaneously emit radiation. We call these unstable

isotopes radioactive isotopes, radioisotopes, or nuclides.

2.

o Spontaneous decay (natural emission of radiation) bya nuclide (radioactive isotope) involves the release ofparticles and/or energy from the nucleus.

o Each radioactive isotope has a specific decay mode(the kind of particle or energy it gives off from itsunstable nucleus) (Tables N and O!)

alpha decay: release of alpha particles

beta decay: release of beta particles

positron emission: release of positrons

gamma radiation : release of gamma rayso These emissions differ in mass, charge, ionizing

power, and penetrating power.

o Determine decay mode and write nuclearequations showing alpha decay, beta decay,positron emission, and gamma radiation(*Remember to put radioactive emissions on the RIGHTside of the arrow – if something is released, it goes on theright)

o Compare and contrast the 4 different types ofradiation in terms of mass, charge, ionizing power,and penetrating power.

3.

o Each radioactive isotope has a specific half-life (rate ofdecay). The half-life is the time it takes for half of theradioisotope to decay/transmute into something morestable). (Table N)

o Calculate the initial amount, the fraction remaining,time elapsed, or the half-life of a radioactiveisotope, given the other variables

4.

o Nuclear reactions are represented by equations thatinclude symbols for elements and radioactive emissions(with mass number in upper left and charge/atomicnumber in lower left)

o These reactions show conservation of mass andcharge

o Complete nuclear equations and predict missingparticles in nuclear equations

o Write nuclear equations given word problems

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5.

o A change in the nucleus of an atom that changes itfrom one element to another is called transmutation.This can occur naturally or can be done artificially bybombarding the nucleus with high-energy particles.

o Distinguish between natural transmutation (onereactant) and artificial transmutation (tworeactants) given nuclear equations

6. o Types of nuclear reactions include fission and fusion.

Fission and fusion can be natural or artificialtransmutations.

o Compare and contrast fission and fusion reactions.o Distinguish between fission and fusion reactions

given nuclear equations

7.

o Nuclear changes convert matter into energy(E = mc2)

o Energy released during nuclear reactions is muchgreater than the energy released during chemicalreactions.

o Compare and contrast chemical reactions andnuclear reactions

o Describe benefits of using nuclear fission

8.

o There are risks and problems associated withradioactivity and the use of radioactive isotopes,including: biological exposure, long-term storage anddisposal problems, and nuclear accidents which releaseradioactive materials into the environment.

o Describe the risks and problems associated withusing radioactive isotopes

9.

o In addition to using nuclear fission for nuclear power, radioactive isotopes have other beneficial uses in medicineand industrial chemistry, including:

radioactive dating (ages of once-living things can be found from the ratio of C-14 to C-12 in the remains; ages of rocks can befound from the ratio of U-238 to Pb-206)

tracing chemical and biological processes (radioactive tracers can be injected into the body and then x-rayed. The radioactive substance will show up on the x-ray and if there are problems, they can be detected easily)

detecting and treating of disease (Sr-90: diagnosing and treating bone cancer; I-131: diagnosing and treating thyroid disorders; Co-60: cancer treatment

radiation can be used to kill bacteria in foods (used with spices, meats, produce)

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Lesson 1: Stability & Radioactivity

Review: Isotopes are

Stability of Nuclei:

Large atoms are considered elements with an atomic > 83. They are

In small atoms the nucleus is stable and therefore are

o Exception to “Small Atom Rule:” -

Example: C-12 & C-14

Nuclear Chemistry is the

Natural radioactivity occurs when nuclei are unstable.

For any element, an isotope that is unstable is called a radioisotope.

A Geiger counter can be used to detect radiation given off by radioactive isotopes.

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Isotopes: Some elements come in several different forms. Take uranium, for example. Most uranium is uranium-‐238. It has 92 protons and 146 neutrons (92 + 146 = 238). But there are several other kinds of uranium. They all have 92 protons, but the number of neutrons differs. They are isotopes of uranium. Some isotopes are more stable then others. These unstable isotope called radioisotopes and will decay spontaneously to form more stable products. As a general rule the following isotopes are radioisotopes or unstable:

. Any isotopes with an atomic number greater than 83 is naturally radioactive.

. When an isotope has a mass that is not its typical mass (the mass on the reference table) is radioactive.

Fill out the chart. Give the correct number of protons, atomic notation, and predict the stability of each isotope.

Unstable

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Classwork 12-1: Nuclear Stability

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Example: A sample of I-131 decays to 1.0 grams in 40 days. What was the mass of the original

sample?

Half-life of I-131 from Table N =8.07 days. 40days/8 days=5 half life decays

½ ½ ½ ½ ½

1.0g2.0g4.0g8.0g16.0g32.0g

Example: What is the total number of hours required for Potassium-42 to undergo three half

life periods?

From Table N K-42 half life=12.4 hours

12.4 hours x 3= 37.2 hours

Example: What mass of a 32.0 g sample of 32P will remain after 71.5 days of decay?

From Table N half-life of P-32=14.3days 71.5 days/14.3 days=5 half lives

½ ½ ½ ½ ½

32.0g16.0g8.0g4.0g2.0g2.0g

Radioisotopes are used for various things:

Lesson 2: Half-Life

Radioactive substances decay at a rate that is

The Half-life is the

The shorter the half life of an isotope the less stable it is.

The longer the half life of an isotope the more stable it is.

Table N lists common radioactive isotopes as well as their half-lives and modes.

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Smoke detectors

C-14

Medical ApplicationsMust haveTc-99/Co-60

I-131

Dangers of radioactivity

Check your understanding

1) After 60 days, 10.0 grams of radioactive isotope remains from an original 80.0 g sample. What

is the half life of this element?

2) In a nuclear reaction, the particle may be spontaneously released from the nucleus of an atom

resulting in the transmutation of the atom into another element.

a) According to the Selected Radioisotopes table, what is the half life of C-14?

b) What mass of 10.0 g sample of C-14 remains after 11,460 years have evolved?

3) A radioactive element has a half life of 2 days. What is the fraction of the original sample will

remain after six days?

Virtual Lab: How can you simulate the radioactive half-

life of an element?

This lab is located at: http://glencoe.mcgraw-hill.com/sites/dl/free/0078693896/280405/E18.html

Background Information:

The rate of decay of a radioactive isotope of an element is measured in terms of its half-

life. When a radioactive isotope decays, the decayed atoms form a daughter product. The half-

life of a radioactive element is the time it takes for half of its atoms to decay into the daughter

product. After two half-lives, one-fourth of the original isotope’s atoms remain, and three-fourths

have turned into the daughter product. After many more half-lives, a very small amount of the

original parent isotope remains, and almost all of it has decayed into the daughter product.

Each radioactive isotope has its own characteristic half-life. For instance, the naturally

occurring radioactive isotope of uranium (U-238) decays into thorium-234 with a half-life of 4.5

billion years. This means that half of the original amount of uranium-238 still remains after this

time. In contrast, some radioactive isotopes decay quickly. For instance, polonium-214 has a

half-life of 0.00016 seconds!

Objectives: In this Virtual Lab you will investigate the meaning of radioactive half-life as you

see a simulation of the radioactive decay of isotopes of four hypothetical elements.

Collect radioactive decay rate data for hypothetical isotopes over a period of

20,000 years.

Determine, compare, and contrast half-lives of four radioactive elements.

Procedure:

1. Click the Video button. Watch the video to find out about atoms. Write your observations in

the Journal.

2. Select one of the four elements from the pull down menu. Note: At first you will see 100

radioactive atoms on the screen.

3. Click the Years Passed button to advance the time 1000 years.

4. Click the Count the Remaining Radioactive Atoms button to see how many radioactive

atoms remain.

5. At any time you can click the Remove Atoms No Longer Radioactive button to remove the

daughter atoms.

6. Record your data in the data table.

7. Continue to advance the time by 1000-year intervals until you have determined the half-life

of the element.

8. After you have completed the Table for the element you chose, click the Graph button to plot

your data.

9. Repeat these steps for the three remaining elements.

10. Complete the Questions.

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http://glencoe.mcgraw-hill.com/sites/dl/free/0078693896/280405/E18.html

Data Table:

Remaining Radioactive Atoms

Years Element A Element B Element C Element D

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

11,000

12,000

13,000

14,000

15,000

16,000

17,000

18,000

19,000

20,000

Questions:

1) According to your data, what are the approximate half-lives of the elements A, B, C, and D?

A:

B:

C:

D:

2) What part of an original isotope’s number of atoms remains have two half-lives?

3) What happens to a radioactive isotope as it decays? Does the radioactive material disappear? Explain.

4) After three half-lives of an isotope, 1 billion (one-eighth) of the original isotope’s atoms still remain in

a certain amount of this element. How many atoms of the daughter product would you expect to be

present?

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Use the chart below as a template to solve every half-life problem

Example:

20 minutes

40 minutes

60 minutes

80 minutes

100 minutes

1.00 g

0.5 g

0.25 g

0.125 g

0.0625 g

Classwork 12-2:

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1. How long does it take a 100.00g sample of

Au-l 98 to decay to 6.25g? 2. How many half-lives will pass by the time a

60.0g sample of Co-60 decays to 7.5g?

3. How long does it take a 180g sample of

Au-198 to decay to 1/8 its original mass?

4. What fraction of a sample of N-16 remains

undecayed after 35.65 seconds?

5. What is the half-life of a radioactive isotope

if a 500.0g sample decays to 62.5g in 24.3

hours?

6. What is the half-live of a radioactive

isotope if it takes 6.2 days for a 72g sample

to decay to 18g?

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7. How many half-lives of K-37 will pass after

6.15 seconds?

8. What fraction of Pu-239 (an artificially produced isotope

used as a fuel in some nuclear fission reactors) remains undecayed after 72,300 years?

9. If a 700.00g sample of I-131 decays to

43.75g, how much time has passed?

10. How long will it take a 3.5g sample of

Fr-220 to decay so that only 1/4 of the original

amount of Fr-220 remains?

11. What is the half-life of a radioisotope if

1/16 of it remains undecayed after 26.4 days?

12. If a radioactive sample of a pure

material decays from 600g to 75g in 42.9

days, what radioisotope could be in the sample?

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13. Co-60 is used in some cancer radiation

therapies. What fraction of a sample of Co-60

will remain undecayed after 5.271 years?

14. Sr-90 is a common waste product of

nuclear fission reactors. How many half-lives

of Sr-90 will pass after 116.4 years?

15. How many years would it take for a 1.000g

sample of U-238 to decay to about 3.9 mg?

16. If 13.125g of K-42 remains undecayed

after 37.08 hours, what was the

original sample size?

17. What is the half-life of a radioactive

isotope if 1/32 of it remains undecayed after

7.5 days?

18. If your cellar was measured to contain 2.400g

of Rn-222 (a radioactive gas naturally produced by some granite deposits), how long would it take for that sample to decay to 0.15g?

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19. 20.

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Multiple Choice:

Classwork 12-2(con't): Uses for Radioisotopes

Radiation is used by doctors to diagnose illness and helps archaeologists find the age of ancient artifacts. Electricity produced by nuclear fission -‐-‐ splitting the atom -‐-‐ is one of its greatest uses. A reliable source of electricity is needed to give us light, help to groom and feed us, and to keep our homes and businesses running. Let me give you some specific examples of how the radiation has been used to -‐-‐

• Diagnose and treat illnesses• Kill bacteria and preserve food without chemicals and refrigeration• Process sludge for fertilizer and soil conditioner• Locate underground natural resources and tell a dry hole from a gusher• Make smoke detectors, nonstick fry pans, and ice cream• Grow stronger crops• Power satellites and provide future electrical needs for space laboratories with

people on board• Design instruments, techniques, and equipment; measure air pollution• Prove the age of works of art and assist in determining their authenticity

RADIATION IN MEDICINE X-‐rays are a type of radiation that can pass through our skin. Our bones are denser than our

skin, so when x-‐rayed, bones and other dense materials cast shadows that can be detected on photographic film. The effect is similar to placing a pencil behind a piece of paper and holding them in front of a light. The shadow of the pencil is revealed because most light has enough energy to pass through the paper, while the denser pencil stops all the light. The difference is that we need film to see the x-‐rays for us.

Today, doctors and dentists use x-‐rays to see structures inside our bodies. This allows them to spot broken bones and dental problems. X-‐ray machines have now been connected to computers in the development of machines called CAT scanners. These instruments provide doctors with color TV pictures that show the shape of internal organs. Approximately 10 million nuclear medicine procedures are performed in the United States annually. Diagnostic x-‐rays and or radiation therapy were administered to about seven out of every 10 Americans. Medical procedures using radiation have saved thousands of lives through the detection and treatment of conditions ranging from hyperthyroidism to bone cancer.

In such procedures, doctors administer slightly radioactive substances to patients, which are attracted to certain internal organs such as the pancreas, kidney, thyroid, liver, or brain, to diagnose clinical conditions. Moreover, radiation is often used to treat certain types of cancer. Radioactive iodine, specifically iodine-‐131, is being used frequently to treat thyroid cancer, a disease which strikes about 11,000 Americans every year. RADIATION IN SCIENCE

Radiation is used in science in many ways. Just as doctors can label substances inside people's bodies, scientists can label substances that pass through plants, animals, or our world. This allows us to study such things as the paths that different types of air and water pollution take through the environment.

It has also helped us learn more about a wide variety of things, such as what types of soil different plants need to grow, the size of newly discovered oil fields, and the track of ocean currents.

Scientists use radioactive substances to find the age of ancient objects by a process called carbon dating. For example, in the upper levels of our atmosphere, cosmic rays hit nitrogen atoms and form a naturally radioactive isotope called carbon-‐14. Carbon is found in all living things, and a small percentage of this carbon is carbon-‐14. When a plant or animal dies, it no longer takes in new carbon and the carbon-‐14 it contains begins the process of radioactive decay.

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However, new isotopes of carbon-‐14 continue to be formed in our atmosphere, and after a few years the percent of radioactivity in an old object is less than it is in a newer one. By measuring this difference, scientists are able to determine how old certain objects are. The measuring process is called carbon dating. RADIATION IN INDUSTRY

We could talk all day about the many and varied uses of radiation in industry and not complete the list. To make a long story short, we'll just concentrate on a few. Exposure to some types of radiation (for example, x-‐rays) can kill germs without harming the items that are being disinfected or making them radioactive. For example, when treated with radiation, foods take much longer to spoil, and medical equipment such as bandages, hypodermic syringes, and surgical instruments don't have to be exposed to toxic chemicals or extreme heat to be sterilized. Although we now use chlorine, a toxic and difficult-‐to-‐handle chemical, we may use radiation in the future to disinfect our drinking water and even kill all the germs in our sewage. Ultraviolet light is already being used to disinfect drinking water in some homes.

The agricultural industry makes use of radiation to improve food production. Plant seeds, for example, have been exposed to radiation to bring about new and better types of plants. Besides making plants stronger, radiation can also be used to control insect populations, thereby decreasing the use of pesticides. Engineers use radioactive substances to measure the thickness of materials and an x-‐ray process called radiography to find hard to detect defects in many types of metals and machines. Radiography is also used to check such things as the flow of oil in sealed engines and the rate and way various materials wear out. And we've already talked about the use of the radioactive element uranium, which is used as a fuel to make electricity for our cities, farms, towns, factories, etc.

In outer space, radioactive materials are also used to power spacecraft. Such materials have also been used to supply electricity to satellites sent on missions to the outermost regions of our solar system. Radiation has been used to help clean up toxic pollutants, such as exhaust gases from coal-‐fired power stations and industry. Sulfur dioxides and nitrogen oxides, for example, can be removed by electron beam radiation.

As you can see, radiation and radioactive materials have played and will continue to play a very significant role in our lives. Let's sum up this discussion with a walk through the life of a typical family for one day and learn about some of the uses of radiation.

Dad gets up in the morning and puts on a clean shirt. His polyester-‐cotton blend shirt is made from chemically treated fabric that has been irradiated (treated with radiation) before being exposed to a soil-‐releasing agent. The radiation makes the chemicals bind to the fabric, keeping his shirt fresh and pressed all day. The shirt is not radioactive.

In the kitchen, Jenny is frying an egg. That nonstick pan she is using has been treated with gamma rays, and the thickness of the eggshell was measured by a gauge containing radioactive material before going into the egg cartoon. Thin, breakable eggs were screened out. The turkey Mom is taking out of the refrigerator for tonight's dinner was covered with irradiated polyethylene shrink-‐wrap. Once polyethylene has been irradiated, it can be heated above its usual melting point and wrapped around the turkey to provide an airtight cover.

As Dad drives to work, he passes reflective signs that have been treated with radioactive tritium and phosphorescent paint. During lunch, brother Bob has some ice cream. The amount of air whipped into that ice cream was measured by a radioisotopic gauge. After you and your family return home this evening, some of you may have soda and others may sit and relax. Nuclear science is at work here: The soda bottle was carefully filled -‐-‐ a radiation detector prevented spillover. And your family is safe at home because the ionizing smoke detector, using a tiny bit of americium-‐241, will keep watch over you while you sleep.

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1. How can we use radioactive isotopes to detect illness?

2. How can we use radiation to detect weakness in the construction of buildings?

3. Have you ever had a bone x-‐ray? Teeth x-‐rayed? How did this help your doctor ordentist treat you?

4. Do you think additional radiation received when people have medical x-‐rays, about40 millirems per year, is worth the benefits they receive?

5. Are there advantages to using radiation instead of pesticides to control pests, suchas insects?

Multiple Choice: 1. _____ The decay of which radioisotope can be used to estimate the age of the

fossilized remains of an insect? 1. Rn-‐2222. I-‐131

3. Co-‐604. C-‐14

2. _____ Which radioisotope is used for diagnosing thyroid disorders?1. U-‐2382. Pb-‐206

3. I-‐1314. Co-‐60

3. _____ Cobalt-‐60 and idodine-‐131 are radioactive isotopes that are used in1. Dating geological formations2. Industrial measurements3. Medical procedures4. Nuclear power

4. _____ Which radioactive isotope is used in treating cancer?1. Carbon-‐142. Cobalt-‐60

3. Lead-‐2064. Uruanium-‐238

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5. _____ The course of a chemical reaction can be traced by using a1. Polar molecule2. Diatomic molecule

3. Stable isotope4. Radioisotope

Constructed Response: Base your answer to the next 3 questions on the information below and on your knowledge of chemistry.

Cobalt-‐60 is commonly used as a source of radiation for the prevention of food spoilage. Bombarding cobalt-‐59 nuclei with neutrons produces the nuclide cobalt-‐60. A food irradiation facility replaces the cobalt-‐60, a source of gamma rays, when the radioactivity level falls to 1/8 of its initial level. The nuclide cesium-‐137 is also a source of radiation for the prevention of food spoilage

1. Complete the nuclear equation below for the decay of cesium-‐137. Your responsemust include the symbol, atomic number, and mass number of the missing particle.

13755 𝐶𝑠 à 0−1𝑒 + _______________

2. Determine the total number of years that elapse before an original cobalt-‐60 sourcein an irradiation facility must be replaced.

3. Identify one emission spontaneously released by a cobalt-‐60 nucleus.

_________________________________________________________________________________________________

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Lab Activity - Radioactive M&Ms

Pre-Lab Questions:

1. On the periodic table, the number for carbon is ______, and the atomic mass is________. What do each of these numbers tell us?

2. Give the term for an element that has the same atomic number, but differentatomic mass: ________________________.

3. What particle in the nucleus is responsible for this difference in mass?

4. Some isotopes are stable. What does this mean?

5. Some isotopes are unstable. What does this mean?

6. What is the atomic mass number for the stable isotope of carbon?

7. What is the atomic mass number for the unstable isotope of carbon?

8. What is given off by unstable isotopes?

9. During radioactive decay, the __________ isotope decays into a ____________isotope that has a different ___________________ number.

Materials: M&M™ or Skittles candy pieces, resealable bag, graph paper

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Procedures: 1. Place 50 atoms of candium (pieces of candy) in the bag.2. Seal the bag and gently shake for 10 seconds.3. Gently pour out candy.4. Count the number of pieces with the print side up—and record the data.

These atoms have "decayed".5. Return only the pieces with the print side down to the bag. Reseal the bag.6. Consume the "decayed atoms”.7. Gently shake the sealed bag for 10 seconds.8. Continue shaking, counting, and consuming until all the atoms have

decayed.9. Graph the number of undecayed atoms vs. time.

Trial Number of Atoms Decayed

Number of undecayed atoms remaining

Class Total Class Average

O

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

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Graph:

Conclusion:

1. What is a half-life?

2. In the experiment, what was the half-life of the element candium?

3. At the end of two half-lives, what fraction of the atoms had not decayed?

4. Describe the shape of the curve drawn. Repeat the experiment threemore times, starting with 30 atoms, 80 atoms, and 100 atoms of candium.Compare the resulting graphs.

5. Repeat the experiment using half-lives of 5 seconds, 20 seconds, and 1minute. Compare the resulting graphs.

If time allows complete Question 4 and/or 5 below

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Lesson 3A: Introduction to Transmutation

Transmutation is defined as

This change always turns the unstable element into a more stable element.

There are two types of transmutation.

Natural Transmutation Begins with one unstable nucleus that spontaneously decays.

****always have ONE REACTANT.

Artificial Transmutation is caused by bombarding a

These reactions always have

Transmutation of one element into another requires a change in the structures of the nuclei of

the atoms involved. This results in the release (or gain) of radioactive decay particles

How are the particles defined? Alpha, Beta and Gamma can be separated using an electric or magnetic field

Positively charged

Negatively charged

Gamma rays and neutrons

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Writing Nuclear Equations

Nuclear reactions obey laws of

The

The decay modes can be found on Table N.

Alpha Decay:

Alpha decay:

Example: 238U undergoes alpha decay

92238U 2

4He + 90234Th

The total mass on the left must equal the total mass on the right (238 = 4 + 234)

The total charge on the left must equal the total charge on the right (92 = 2 + 90)

Lesson 3B: Transmutation - Nuclear Equations

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Beta decay:

Beta (minus) decay:

Example: 234Th undergoes beta decay

90234Th -1

0e + 91 234Pa

The total mass on the left must equal the total mass on the right (234 = 0 + 234)

The total charge on the left must equal the total charge on the right (90 = -1 + 91)

Positron Emission:

Positron (beta plus) decay:

Example: 37K undergoes positron decay

19 37K +1

0e + 1837Ar

The total of the mass numbers on the left must equal the total on the right (37 = 0 + 37)

The total charge on the left must equal the total charge on the right (19 = 1 + 18)

Gamma Rays:

This makes them the most destructive form of nuclear radiation.

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Check your understanding:

1. Complete the example problems below showing alpha decay (remember, CHARGE and MASS must be

conserved!)

a. 220 4

Fr + He

87 2

b. 222

Rn +

86

2. Complete the example problems below showing beta decay:

a. 32 0

P + e

15 -1

b. 14

C +

6

3. Complete the example problems showing positron emission:

a. 37 0

K + e

19 +1

b. 81

Rb

37 +

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Classwork 12-4:Complete the following decay equations and indicate the type of Decay

Type of Decay

1) 247 243

Cm Pu +

96 94 ___________ __________________

2) 243 243

Pu Am +

94 95 ___________ __________________

3) 243 239

Am N p95 93 ___________ __________________

4) 239 239

Np U +

93 92 ___________ __________________

5) 239 235

U Th +

92 90 ___________ __________________

6) 235 235

Th Pa +

90 91 ___________ __________________

7) 235 235

Pa Th +

91 90 ___________ __________________

+

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8) 235 231

Th Ra +

90 88 ___________ __________________

9) 231 231

Ra Fr +

88 87 ___________ __________________

10) 231 227

Fr At +

87 85 ___________ __________________

More Problems:

11)

12)

13)

14)

15)

16)

17)

18)

19)

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1. Alpha particles are emitted during the radioactivedecay of

1. carbon-142. neon-193. calcium-374. radon-222

2. Which nuclear reaction is classified as alphadecay?

3. Which substance has chemical properties similarto those of radioactive 235U?

1. 235Pa2. 233Pa3. 233U4. 206Pb

4. The change that is undergone by an atom of anelement made radioactive by bombardment with high-energy protons is called

1. natural transmutation2. artificial transmutation3. natural decay4. radioactive decay

5. Which type of radioactive emission has a positivecharge and weak penetrating power?

1. alpha particle2. beta particle3. gamma ray4. neutron

6. Given the reaction:Which type of reaction is represented?

1. natural transmutation2. artificial transmutation3. fission4. fusion

7. Given the nuclear reaction:

Which isotope is represented by the X when the equation is correctly balanced?

1.

2.

3.

4.

8. Given the nuclear reaction:What does X represent in this reaction?

1.

2.

3.

4.

9. Which equation is an example of artificialtransmutation?

1. + + 2. U + 3F2 UF6

3. Mg(OH)2 + 2HCl 2H2O + MgCl2

4. Ca + 2H2O Ca(OH)2 + H2

10. In the reaction:

the X represents

1. an alpha particle2. a beta particle3. an electron4. a proton

11. Which nuclear equation represents artificialtransmutation?

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12. Which particle cannot be accelerated in amagnetic field?

1. alpha particle2. beta particle3. neutron4. proton

13. Given the nuclear equation:

What is the identity of particle X in this equation?

14. Given the equation:When the equation is balanced correctly, which particle is represented by X?

1.

2.

3.

4.

15. Bombarding a nucleus with high-energyparticles that change it from one element into another is called

1. a half-reaction2. a breeder reaction3. artificial transmutation4. natural transmutation

16. Which process converts an atom from oneelement to another, when the nucleus of an atom is bombarded with high-energy particles?

1. artificial transmutation2. natural transmutation3. addition polymerization4. condensation polymerization

17. What is the name of the process in which thenucleus of an atom of one element is changed into the nucleus of an atom of a different element?

1. decomposition2. transmutation3. substitution4. reduction

18. Given the reaction:Which particle is represented by X?

1. alpha2. beta3. neutron4. proton

19. Which particle is represented by the letter X ?

1. an alpha particle2. a beta particle3. a neutron4. a proton

20. In the equation:

the symbol X represents

21. Which type of radiation has neither mass norcharge?

1. gamma2. neutron3. alpha4. beta

22. Which radioisotope is a beta emitter?

1. 90Sr2. 220Fr3. 37K4. 238U

32

23. Which kind of particle, when passed through anelectric field, would be attracted to the negative electrode?

1. an alpha particle2. a beta particle3. a neutron4. an electron

24. Which kind of radiation will travel through anelectric field on a pathway that remains unaffected by the field?

1. a proton2. a gamma ray3. an electron4. an alpha particle

25. Which equation represents nucleardisentegration resulting in release of a beta particle?

26. Which of these types of nuclear radiation has thegreatest penetrating power?

1. alpha2. beta3. neutron4. gamma

27. Given the nuclear reaction:

This reaction is an example of

1. fission2. fusion3. artificial transmutation4. natural transmutation

28. Which type of radiation would be attracted tothe positive electrode in an electric field?

1.

2.

3.

4.

29. Which radioactive emanations have a charge of2+?

1. alpha particles2. beta particles3. gamma rays4. neutrons

30. In Rutherford's gold foil experiments, somealpha particles were deflected from their original paths but most passed through the foil with no deflection. Which statement about gold atoms is supported by these experimental observations?

1. Gold atoms consist mostly of empty space.2. Gold atoms are similar to alpha particles.3. Alpha particles and gold nuclei have opposite

charges.4. Alpha particles are more dense than gold

atoms.

33

Lesson 4: Energy and Nuclear Reactions

Nuclear fusion and nuclear fission are two different types of energy-releasing reactions in

which energy is released from high-powered atomic bonds between the particles within the

nucleus. The main difference between these two processes is that fission is the splitting of an

atom into two or more smaller ones while fusion is the fusing of two or more smaller atoms into

a larger one.

Fission Reactions involve the

Fission reactions produce/capture neutrons. They can become involved in another

fission reaction.

235U + 1n 90Sr + 143Xe + 31n

More neutrons are released to keep the reaction going. If the number of neutrons released is

not controlled a chain reaction will occur. This is the type of reaction used in nuclear bombs.

NOTE: ENERGY is also produced in the above nuclear reaction

All nuclear reactors are devices designed to maintain a chain reaction producing a steady flow

of neutrons generated by the fission of heavy nuclei.

Watch this: http://www.youtube.com/watch?v=BdbitRlbLDc

http://www.diffen.com/difference/Covalent_Bonds_vs_Ionic_Bonds

http://www.euronuclear.org/info/encyclopedia/chainreaction.htm

http://www.euronuclear.org/info/encyclopedia/n/neutron.htm

http://www.euronuclear.org/info/encyclopedia/n/nuclear-fission.htm

34

Fusion Reactions involve

2H + 3H 4He + 1n

Hydrogen atoms combine to form helium in a star.

In fission and fusion reactions,

The energy of nuclear reactions is much greater than the energy associated with chemical

reactions.

ENERGY IS PRODUCED AS A PRODUCT IN BOTH FUSION & FISSION REACTIONS!

The energy of

One disadvantage of Fission à

Disadvantages of Fusion à

Nuclear reactions produce

35

Nuclear Fission Nuclear Fusion

Definition: Fission is the splitting of a large atom into two

or more smaller ones.

Fusion is the fusing of two or more lighter

atoms into a larger one.

Natural occurrence of

the process:

Fission reaction does not normally occur in

nature.

Fusion occurs in stars, such as the sun.

Byproducts of the

reaction:

Fission produces many highly radioactive

particles.

Few radioactive particles are produced by

fusion reaction, but if a fission "trigger" is

used, radioactive particles will result from

that.

Conditions: Critical mass of the substance and high-speed

neutrons are required.

High density, high temperature environment is

required.

Energy Requirement: Takes little energy to split two atoms in a

fission reaction.

Extremely high energy is required to bring two

or more protons close enough that nuclear

forces overcome their electrostatic repulsion.

Energy Released: The energy released by fission is a million

times greater than that released in chemical

reactions; but lower than the energy released

by nuclear fusion.

The energy released by fusion is three to four

times greater than the energy released by

fission.

Nuclear weapon: One class of nuclear weapon is a fission bomb,

also known as an atomic bomb or atom bomb.

One class of nuclear weapon is the hydrogen

bomb, which uses a fission reaction to "trigger"

a fusion reaction

Classwork 12-5:

1

2

3

4

18

Unit Review

37

19

Unit Review continued

38

41

Vocabulary Practice: Match each item with the correct statement below.

a. positronb. alpha particlec. beta particle

d. artificial transmutatione. gamma radiationf. fusion

g. fissionh. natural transmutationi. radioisotope

____ 1. emitted helium nucleus ____ 2. energetic electron from decomposed neutron ____ 3. high-energy rays (photons) emitted by a radioisotope ____ 4. particle of charge +1 and mass equal to that of an electron ____ 5. conversion of an atom of one element to an atom of another element as a result of natural radioactivity ____ 6. combination of two nuclei to form a nucleus of greater mass ____ 7. splitting of nucleus into smaller fragments ____ 8. Conversion of an atom of one element to an atom of another element resulting from bombarding a

nucleus with a high-energy particle, such as a neutron or an alpha particle ____ 9. A “bad” ratio of neutrons:protons resulting in an unstable nucleus that is radioactive

Multiple Choice Identify the number of the choice that best completes the statement or answers the question.

____ 1. An unstable nucleus ____. (1) increases its nuclear mass by fission (3) emits energy when it decays (2) increases its half-life (4) expels all of its protons

____ 2. The charge on a gamma ray is ____. (1) +2 (3) 0 (2) 1 (4) 2

____ 3. What particle is emitted in alpha radiation? (1) electron (3) helium nucleus (2) photon (4) hydrogen nucleus

____ 4. A beta particle is a(n) ____. (1) photon (3) helium nucleus (2) electron (4) hydrogen nucleus

____ 5. What is the change in atomic mass when an atom emits a beta particle? (1) decreases by 2 (3) remains the same (2) decreases by 1 (4) increases by 1

____ 6. What is the change in atomic mass when an atom emits gamma radiation? (1) decreases by 2 (3) remains the same (2) decreases by 1 (4) increases by 1

____ 7. The least penetrating form of radiation is ____. (1) beta radiation (3) alpha radiation (2) gamma radiation (4) positron

Optional - Unit Review/Practice

42

____ 8. Half-reactions can be written to represent all (1) double-replacement reactions (3) fission and fusion reactions (2) neutralization reactions (4) oxidation and reduction reactions

____ 9. Which symbol is used for an alpha particle? (1) He (3) He

(2) He (4) He

____ 10. What symbol is used for beta radiation? (1) e (3) e

(2) e (4) e

____ 11. Which nuclide is used to investigate human thyroid gland disorders? (1) carbon-14 (3) cobalt-60 (2) potassium-37 (4) iodine-131

____ 12. When radium-226 (atomic number 88) decays by emitting an alpha particle, it becomes ____. (1) polonium-222 (3) radium-222 (2) polonium-224 (4) radon-222

____ 13. What determines the stability of atomic nuclei? (1) the ratio of protons to neutrons (2) the ratio of neutrons to protons (3) the ratio of beta particles to neutrinos (4) the ratio of alpha particles to beta particles

____ 14. What particle is needed to complete this nuclear reaction? Rn Po + _____

(1) He (3) H

(2) e (4) n

____ 15. Which reaction converts an atom of one element to an atom of another element? (1) combustion (3) saponification (2) polymerization (4) transmutation

____ 16. What particle is needed to complete the following nuclear equation? Mn ____ + e

(1) Co (3) Fe

(2) Mn (4) Cr

____ 17. To what element does polonium-208 (atomic number 84) decay when it emits an alpha particle? (1) Pb (3) Pb

(2) Po (4) Rn

____ 18. Controlled nuclear chain reactions ____. (1) take place in nuclear reactors (2) are always fusion reactions

(3) never produce radioactive by-products (4) are characteristic of atomic bombs

43

____ 19. A reaction in which small nuclei combine to form a heavier nucleus is called ____. (1) fission (3) background radiation (2) a chemical reaction (4) fusion

____ 20. Nuclear fusion ____. (1) takes place in the sun (3) can be controlled in the laboratory (2) occurs at low temperatures (4) is used in medicine

____ 21. Which nuclide is listed with its half-life and decay mode? (1) K-37, 1.24 h, α (3) Rn-222, 1.6 x 103 y, α (2) N-16, 7.2 s, β- (4) U-235, 7.1 x 108 y, β-

____ 22. Which nuclear emission has the greatest mass? (1) alpha particle (2) beta particle (3) gamma ray (4) positron

____ 23. Alpha particles are emitted during the radioactive decay of (1) carbon-14 (2) neon-19 (3) calcium-37 (4) radon-222

____ 24. After 32 days, 5 milligrams of an 80-milligram sample of a radioactive isotope remains unchanged. What is the half-life of this element? (1) 8 days (2) 2 days (3) 16 days (4) 4 days

____ 25. Given the balanced equation representing a nuclear reaction: Which particle is represented by X? (1) (2) (3) (4)

____ 26. The particle represented by X is (1) (2) (3) (4)

____ 27. Which reaction is an example of natural transmutation? (1) (3) (2) (4)

____ 28. Which nuclear equation represents a natural transmutation? (1) (3) (2) (4)

____ 29. In the reaction , what does X represent? (1) a neutron (2) a proton (3) an alpha particle (4) a beta particle

____ 30. Which balanced equation represents a fusion reaction? (1) (3) (2) (4)

Short Answer 1. If the half-life of a radioactive material is 8 years, how many years will it take for one half of the original amount

of material to decay?

44

2. After 42 days, 2 g of phosphorus-32 has decayed to 0.25 g. What is the half-life of phosphorus-32?

3. The radioisotope radon-222 has a half-life of 3.8 days. How much of a 74-g sample of radon-222 would be left after approximately 15.2 days?

4. After how many days is the amount of radon-222 equal to one-sixteenth of its original amount?

5. If the amount of iodine-131 in a sample is 32 g, how much iodine-131 will remain after 16.04 days?

Base your answers to questions 7 and 8 on the information below.

A substance known as heavy water can be obtained from ordinary water and could be a significant source of energy in the future. Heavy water contains deuterium, H-2. Instead of the two hydrogen atoms in a typical water molecule, a heavy water molecule has two deuterium atoms. In 3.78 kilograms of ordinary water, the percent composition by mass of heavy water is approximately 0.0156%.

Deuterium atoms completely ionize at approximately 108 K. The result is an ionized gas consisting of electrons and deuterons (the nuclei of deuterium). A triton is the nucleus of a tritium atom, H-3. These particles react according to the equations below. In the second equation, X represents an unidentified product.

7.) Calculate the mass of heavy water in a 3.78-kilogram sample of ordinary water. Your response must include both a correct numerical setup and the calculated result.

8.) Identify particle X in the second nuclear equation. Your response must include the symbol, atomic number, and mass number of the particle.

45

Base your answers to questions 9 through 11 on the information below.

Cobalt-60 is commonly used as a source of radiation for the prevention of food spoilage. Bombarding cobalt-59 nuclei with neutrons produces the nuclide cobalt-60. A food irradiation facility replaces the cobalt-60,

a source of gamma rays, when the radioactivity level falls to of its initial level. The nuclide cesium-137 is also

a source of radiation for the prevention of food spoilage.

9.) Identify one emission spontaneously released by a cobalt-60 nucleus.

10.) Determine the total number of years that elapse before an original cobalt-60 source in an irradiation facility must be replaced.

11.) Complete the nuclear equation below for the decay of cesium-137. Your response must include the symbol, atomic number, and mass number of the missing particle.


Scientists are investigating the production of energy using hydrogen-2 nuclei (deuterons) and hydrogen-3 nuclei (tritons). The balanced equation below represents one nuclear reaction between two deuterons.

12.) State, in terms of subatomic particles, how a deuteron differs from a triton.

13.) Identify the type of nuclear reaction represented by the equation.

46

Base your answers to questions 14 through 16 on the information below.

When a uranium-235 nucleus absorbs a slow-moving neutron, different nuclear reactions may occur. One of these possible reactions is represented by the complete, balanced equation below.

For this reaction, the sum of the masses of the products is slightly less than the sum of the masses of the reactants. Another possible reaction of U-235 is represented by the incomplete, balanced equation below.

14.) Identify the type of nuclear reaction represented by equation 1.

15.) Write a notation for the missing product in equation 2.

16.) Determine the half-life of krypton-92 if only 6.0 milligrams of an original 96.0-milligram sample remains unchanged after 7.36 seconds.


The fossilized remains of a plant were found at a construction site. The fossilized remains contain the

amount of carbon-14 that is present in a living plant.

17.) Determine the approximate age of these fossilized remains.

18.) Complete the nuclear equation below for the decay of C-14. Your response must include the atomic number, the mass number, and the symbol of the missing particle.

19.) Given the nuclear equation:

a.) State the type of nuclear reaction represented by the equation.

b.) The sum of the masses of the products is slightly less than the sum of the masses of the reactants. Explain this loss of mass.

c.) This process releases greater energy than an ordinary chemical reaction does. Name another type of nuclear reaction that releases greater energy than an ordinary chemical reaction.

47

Base your answers to questions 20 through 22 on the reading passage below and on your knowledge of chemistry.

A Glow in the Dark, and Scientific Peril The [Marie and Pierre] Curies set out to study radioactivity in 1898. Their first accomplishment was to show

that radioactivity was a property of atoms themselves. Scientifically, that was the most important of their findings, because it helped other researchers refine their understanding of atomic structure.

More famous was their discovery of polonium and radium. Radium was the most radioactive substance the Curies had encountered. Its radioactivity is due to the large size of the atom, which makes the nucleus unstable and prone to decay, usually to radon and then lead, by emitting particles and energy as it seeks a more stable configuration.

Marie Curie struggled to purify radium for medical uses, including early radiation treatment for tumors. But radium’s bluish glow caught people’s fancy, and companies in the United States began mining it and selling it as a novelty: for glow-in-the-dark light pulls, for instance, and bogus cure-all patent medicines that actually killed people.

What makes radium so dangerous is that it forms chemical bonds in the same way as calcium, and the body can mistake it for calcium and absorb it into the bones. Then, it can bombard cells with radiation at close range, which may cause bone tumors or bone-marrow damage that can give rise to anemia or leukemia.

— Denise Grady, The New York Times, October 6, 1998

20.) State one risk associated with the use of radium.

21.) Using information from the Periodic Table, explain why radium forms chemical bonds in the same way as calcium does.

22.) If a scientist purifies 1.0 gram of radium-226, how many years must pass before only 0.50 gram of the original radium-226 sample remains unchanged?

48

Unit Review: Nuclear Chemistry

Place a checkmark next to each item that you can do! If a sample problem is given, complete it as evidence.

_____1. I can still do

everything from Unit 1.





















_____12. I can compare types

of radiation in terms of

symbol, mass number, charge,

penetrating power, shielding

required, and biological

hazard.

Type Symbol Mass

#

Charge Penetrating

Power

alpha

beta

gamma

neutron

positron

49

_____13. I can identify

the three types of nuclear

reactions.

The three types of nuclear reactions are:

a.

b.

c.

_____14. I can define

transmutation, fission, and

fusion.

Definitions:

transmutation

fission

fusion

_____15. I can state two

synonyms for spontaneous

decay.

Two synonyms for spontaneous decay

are:___________________________

and _________________________________.

_____16. I can show how

mass number and electrical

charge must be conserved in

any nuclear reaction.

Complete the following nuclear equation:

________

_____17. I can explain what

makes a nucleus stable or

unstable.

The stability of the nucleus is dependent on the ______________ to

_________________ ratio.

_____18. I can explain the

difference between natural

transmutation and artificial

transmutation.

The difference between natural transmutation and artificial transmutation

is that in natural transmutation an_____________ __________breaks

apart on its own and in artificial transmutation a _____________

___________ is made ________________ by hitting it with a high

energy particle (such as a proton, neutron, or gamma radiation).

_____19. I can identify a

natural decay reaction from a

list of reactions.

Which equation represents a natural decay?

50

_____20. I can identify

an artificial

transmutation reaction

from a list of reactions.

Which equation represents artificial transmutation?


fission reaction from a list of

reactions.

Which equation represents fission?


fusion reaction from a list of

reactions.

Which equation represents fusion?

51

_____24. Given a list of

reactions, I can differentiate a

“nuclear” reaction from a

“chemical” reaction.

Which of the following equations represent NUCLEAR reactions?

_____25. I can define half-life.

Definition:

half-life

_____26. Given the length of

the half-life and the amount of

time that has passed, I can

determine the amount of

radioactive sample.

Based on Reference Table N, what fraction of a radioactive sample of

Au-198 will remain unchanged after 10.78 days?

What was the original mass of a radioactive sample of K-37 if the sample

decayed to 25.0 g after 4.92 seconds? The half-life of K-37 is 1.23

seconds)

_____27. Given the length of

the half-life and the amount of

radioactive sample, I can

determine the amount of time

that has passed.

A 100.0 g sample of Co-60 decays until only 12.5 g of it remains. Given

that the half-life of Co-60 is 5.271 years, how long did the decay take?

_____28. Given the amount of

time that has passed and the

amount of radioactive sample,

I can determine the length of

the half-life.

What is the half-life of a radioisotope if 25.0 g of an original 200.0 g

sample remains unchanged after 11.46 days?

_____29. Using Table N, I can

determine the length of half-

life and/or decay mode for a

specific radioactive isotope.

Compared to K-37, the isotope K-42 has

A) shorter half-life and the same decay mode

B) shorter half-life and a different decay mode

C) longer half-life and the same decay mode

D) longer half-life and a different decay mode

52

_____30. I can state 5

beneficial uses for radioactive

isotopes.

Five beneficial uses for radioactive isotopes are:

a.

b.

c.

d.

e.

_____31. I can state the

scientific use of 4 specific

radioactive isotopes.

C-14 is used for _____________________________________________

I-131 is used for_____________________________________________

U-238 is used for ____________________________________________

Co-60 is used for_____________________________________________

_____32. I can state three risks

associated with radioactivity

and radioactive isotopes.

Three risks associated with radioactivity and radioactive isotopes are:

a.

b.

c.

Unit 12: Nuclear Chemistry Practice Test

1. Base your answer to the following question on Given thenuclear equation:

11H + X ® 63Li + 42He

A) 94Li B) 94Be C) 105Be D) 106C

The particle represented by X is

A) 53Fe B) 137Cs C) l98Au D) 220Fr

2. Which isotope will spontaneously decay and emitparticles with a charge of +2?

A) alpha B) betaC) neutron D) positron

3. Which of these particles has the greatest mass?

4. Base your answer to the following question on Given thenuclear equation:

1910Ne ® X + 19 9F

A) alpha B) betaC) neutron D) positron

What particle is represented by X?

A) mass, onlyB) charge, onlyC) both mass and chargeD) neither mass nor charge

5. Alpha particles and beta particles differ in

A) It has a mass of 1 and a charge of 1.B) It has a mass of 0 and a charge of –1.C) It has a mass of 0 and a charge of 0.D) It has a mass of 4 and a charge of +2.

6. Which statement best describes gamma radiation?

A) alpha B) betaC) neutron D) gamma

7. Which type of radiation is most similar to high- energyx-rays?

A) 2865 y B) 5730 yC) 11 460 y D) 17 190 y

8. What is the total number of years that must pass beforeonly 25.00 grams of an original 100.0-gram sample ofC-14 remains unchanged?

A) 14C B) 16N C) 32P D) 37K

9. Which isotope is most commonly used in theradioactive dating of the remains of organic materials?

A) B) C) D)

10.Based on Reference Table N, what fraction of aradioactive 90Sr sample would remain unchanged after56.2 years?

A) 1.91 days and alpha decayB) 1.91 days and beta decayC) 3.82 days and alpha decayD) 3.82 days and beta decay

11. What is the half-life and decay mode of Rn-222?

A) 8 days B) 2 daysC) 16 days D) 4 days

12. After 32 days, 5 milligrams of an 80-milligram sampleof a radioactive isotope remains unchanged. What is thehalf-life of this element?

A) combustion B) polymerizationC) saponification D) transmutation

13. Which reaction converts an atom of one element to anatom of another element?

A) natural transmutationB) artificial transmutationC) nuclear fusionD) nuclear fission

14. Radioactive cobalt-60 is used in radiation therapytreatment. Cobalt-60 undergoes beta decay. This typeof nuclear reaction is called

A) 147N + 10n 146C + 11HB) 23592U + 10n 8735Br + 14657La + 310nC) 22688Ra 22286Ra + 42HeD) 21H + 21H 42He

15. In which reaction is mass converted to energy by theprocess of fission?

A) Heavy nuclei split into lighter nuclei.B) Light nuclei form into heavier nuclei.C) Energy is released and less stable elements are

formed.D) Energy is absorbed and more stable elements are

formed.

16. Which statement best describes what happens in afission reaction?

53

A) form heavier isotopes from lighter isotopesB) form lighter isotopes from heavier isotopesC) convert mass to energyD) convert energy to mass

17. Nuclear fusion differs from nuclear fission becausenuclear fusion reactions

A) less than the mass of the reactants because some ofthe mass has been converted to energy

B) less than the mass of the reactants because some ofthe energy has been converted to mass

C) more than the mass of the reactants because someof the mass has been converted to energy

D) more than the mass of the reactants because someof the energy has been converted to mass

18. In a nuclear fusion reaction, the mass of the products is

A) collisions between nuclei of high atomic numberB) collisions between nuclei of low atomic numberC) the conversion of mass to energyD) the conversion of energy to mass

19. A fission reaction is similar to a fusion reaction in thatboth reactions involve

A) U-238 B) Pb-206C) I-131 D) Co-60

20. Which radioisotope is used for diagnosing thyroiddisorders?

A) carbon-14 B) cobalt-60C) lead-206 D) uranium-238

21. Which radioactive isotope is used in treating cancer?

A) long half-lives and be quickly eliminated by thebody

B) long half-lives and be slowly eliminated by thebody

C) short half-lives and be quickly eliminated by thebody

D) short half-lives and be slowly eliminated by thebody

22. Radioisotopes used for medical diagnosis must have

A) acid rainB) helium gasC) greenhouse gases, such as CO2

D) radioisotopes with long half-lives

23. A serious risk factor associated with the operation of anuclear power plant is the production of

A) radon-222 B) radium-226C) cesium-137 D) cobalt-60

24. Refering to Table N, which substance is a radioactivewaste product that is safest to release into theatmosphere after it has decayed to a safe radiationlevel?

Base your answers to questions 25 through 27 on theinformation below, the Reference Tables for Chemistry,and your knowledge of chemistry.

Radioactivity and radioactive isotopes have thepotential for both benefiting and harming livingorganisms. One use of radioactive isotopes is inradiation therapy as a treatment for cancer. Cesium-137is sometimes used in radiation therapy. A sample of cesium-137 was left in an abandonedclinic in Brazil in 1987. Cesium-137gives off a blueglow because of its radioactivity. The people whodiscovered the sample were attracted by the blue glowand had no idea of any danger. Hundreds of people weretreated for overexposure to radiation, and four peopledied.

25. Suppose a 40-gram sample of iodine-131 and a 40-gramsample of cesium-137 were both abandoned in theclinic in 1987. Explain why the sample of iodine-131would not pose as great a radiation risk to people todayas the sample of cesium-137 would.

26. If 12.5 grams of the original sample of cesium-137remained after 90.69 years, what was the mass of theoriginal sample?

27. Using Reference Table N, complete the equationprovided in your answer booklet for the radioactivedecay of 13755Cs. Include both atomic number and massnumber for each particle.

54

Base your answers to questions 28 through 30 on in the information below.

When a uranium-235 nucleus absorbs a slow-moving neutron, different nuclear reactions mayoccur. One of these possible reactions is represented by the complete, balanced equation below.

Equation 1: 23592U + 10n ® 9236Kr + 14256Ba + 210n + energy

For this reaction, the sum of the masses of the products is slightly less than the sum of themasses of the reactants. Another possible reaction of U-235 is represented by the incomplete,balanced equation below.

Equation 2: 23592U + 10n ® 9238Sr + ____ + 210n + energy28. Determine the half-life of krypton-92 if only 6.0 milligrams of an original 96.0-milligram sample remains

unchanged after 7.36 seconds.

29. Write a notation for the missing product in equation 2.

30. Identify the type of nuclear reaction represented by equation 1.

31. Base your answer to the following question on the information below.

Hydrocarbons and fissionable nuclei are among the sources used for the production of energy inthe United States. A chemical reaction produces much less energy than a nuclear reaction per mole ofreactant. The balanced chemical equation below represents the reaction of one molecule of a hydrocarbonwith two molecules of oxygen.

Chemical equation: CH4 + 2O2 ® CO2 + 2H2O + 1.48 × 10–18 J

The nuclear equation below represents one of the many possible reactions for one fissionablenucleus. In this equation, X represents a missing product.

Nuclear equation: 10n + 23592U ® 8936Kr + X + 310n + 3.36 × 10–11 J

Write an isotopic notation for the missing product represented by X in the nuclear equation.

32. Given the nuclear equation:

5829Cu ® 5828Ni + XWhat nuclear particle is represented by X?

55


Scientists are investigating the production of energy using hydrogen-2 nuclei (deuterons) andhydrogen-3 nuclei (tritons). The balanced equation below represents one nuclear reaction between twodeuterons.

21H + 21H ® 32He + 10n + 5.23 × 10–13 J33. Identify the type of nuclear reaction represented by the equation.

34. State, in terms of subatomic particles, how a deuteron differs from a triton.

35. Base your answer to the following question on the information below.

A battery-operated smoke detector produces an alarming sound when its electrical sensor detectssmoke particles. Some ionizing smoke detectors contain the radioisotope americium-241, whichundergoes alpha decay and has a half-life of 433 years. The emitted alpha particles ionize gasmolecules in the air. As a result, an electric current flows through the detector. When smoke particlesenter the detector, the flow of ions is interrupted, causing the alarm to sound.

Complete the nuclear equation below for the decay of Am-241. Your response must include the symbol,mass number, and atomic number for each product.

Base your answers to questions 36 through 39 on the reading passage below and on your knowledge ofchemistry.

A Glow in the Dark, and Scientific Peril

The [Marie and Pierre] Curies set out to study radioactivity in 1898. Their first accomplishment was toshow that radioactivity was a property of atoms themselves. Scientifically,that was the most important oftheir findings, because it helped other researchers refine their understanding of atomic structure. Morefamous was their discovery of polonium and radium. Radium was the most radioactive substance theCuries had encountered. Its radioactivity is due to the large size of the atom, which makes the nucleusunstable and prone to decay, usually to radon and then lead, by emitting particles and energy as it seeks amore stable configuration.Marie Curie struggled to purify radium for medical uses, including earlyradiation treat-ment for tumors. But radiums bluish glow caught peoples fancy, and companies in theUnitedStates began mining it and selling it as a novelty: for glow-in-the-dark light pulls, for instance, and boguscure-all patent medicines that actually killed people.What makes radium so dangerous is that it formschemical bonds in the same way as calcium, and the body can mistake it for calcium and absorb it into thebones. Then, it can bombard cells with radiation at close range, which may cause bone tumors orbone-marrow damage that can give rise to anemia or leukemia. - Denise Grady, The New York Times, October 6, 1998

36. If a scientist purifies 1.0 gram of radium-226, how many years must pass before only 0.50 gram of theoriginal radium-226 sample remains unchanged?

37. Using information from the Periodic Table, explain why radium forms chemical bonds in the same way ascalcium does.

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38. Using Reference Table IV, complete the equation for the nuclear

decay of 226Ra. Include both atomic number and mass number 88 for each particle.

39. State one risk associated with the use of Radium.

Base your answers to questions 40 through 43 on the article below, the Reference Tables forPhysicalSetting/Chemistry, and your knowledge of chemistry.

Radioactivity at home You may be surprised to learn that you do not need to visit a nuclear power plant or ahospital X-ray laboratory to find sources of radioactivity. They are all around us. In fact, it islikely that you’ll find a few at home. Your front porch may incorporate cinder blocks orgranite blocks. Both contain uranium. Walk through the front door, look up, and you’ll see asmoke detector that owes its effectiveness to the constant source of alpha particle emissionsfrom Americium-241. As long as the gases remain ionized within the shielded container,electricity flows, and all is calm. When smoke enters the chamber, it neutralizes the chargeson these ions. In the absence of these ions, the circuit breaks and the alarm goes off. Indicator lights on your appliances may use Krypton-85; electric blankets,promethium-147; and fluorescent lights, thorium-229. Even the food we eat is radioactive.The more potassium-rich the food source, the more potassium-40—a radioactive isotope thatmakes up about 0.01% of the natural supply of this mineral—is present. Thus, brazil nuts,peanuts, bananas, potatoes, and flour, all rich in potassium, are radiation sources.—Chem Matters April 2000

40. State one risk or danger associated with radioactivity.

41. State one benefit or useful application of radioactivity not mentioned in this article.

42. How is the radioactive decay of Krypton-85 different from the radioactive decay of Americium-241?

43. Write the equation for the alpha decay that occurs in a smoke detector containing Americium-241(Am-241).

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Answer KeyUnit 11 - Review Packet

1. B2. D3. A4. D5. C6. C7. D8. C9. A10. B11. C12. A13. D14. A15. B16. A17. A18. A19. C20. C21. B22. C23. D24. A25. Responses include,

but are not limited to,these examples:Iodine-131 woulddecay faster • Iodinehas a much shorterhalf-life • Most ofthe I-131 would begone.

26. 10027. Responses include,

but are not limited to,these examples: 13755Cs ® 0–1e + 13756Ba• 13755Cs ® 0–1 + 13756Ba

28. 1.84 s29. xenon-142 or 14254Xe30. fission or

transmutation31. 14456 Ba or

barium-14432. 0+1e or 0+1ß or ß+ or

positron.33. Examples: fusion;

thermonuclear fusion34. Examples: A deuteron

has one neutron and atriton has twoneutrons.; A deuteronhas one fewer neutronthan a triton.

35.

36. 160037. Radium and calcium

are both located inGroup 2 on thePeriodic Table orsame family or 2valence electrons

38. 226Ra 4He + 222Rnor 226Ra 222Rn +4 88 2 86 88 86 2

39. cause bone tumors ordamage bone marrowor can cause leukemiaor anemia orradioactive or DNAdamage or death

40. Acceptable responses:Extensive exposurecan make people sick,contamination ofenvironment,introduction ofradioactive materialsinto the ecosystem

41. Acceptable responses:Radioactivity can beused in medicaldiagnosis and/ortreatment, foodirradiation,radioactive dating.

42. Acceptable responses:85Kr undergoes betadecay and 241Amundergoes alphadecay, Decay modeand half-life aredifferent, half-livesdifferent.

43. 241 95Am ® 42He +237 93Np

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