Chapter 18: Radioactivity & Nuclear Reactions

Georgia Performance StandardsSPS3. Students will distinguish the characteristics

and components of radioactivity.a. Differentiate among alpha and beta particles and gamma radiation.b. Differentiate between fission and fusion.c. Explain the process half-life as related to radioactive decay.d. Describe nuclear energy, its practical application as an alternative energy, and its potential problems.

The Big Idea: Radioactivity

Essential Question:What is the ratio of protons to

neutrons in each of these isotopes of helium? H-3, H-4

RadioactivityIsotopes—atoms of the same element that have different numbers of neutrons

ex: carbon 12, carbon 13, carbon 14The atoms of all isotopes of an element have the same number of electrons, and have the same chemical properties.

RadioactivityMarie Curie named the process by which materials gave off rays radioactivity.Radioactivity—nuclear decay which happens when the strong force is not large enough to hold the protons and neutrons together

nucleus with too many or too few neutrons compared to protons is radioactive

RadioactivityStable and Unstable Nuclei

The ratio of neutrons to protons is related to the stability of the nucleus.

ex: less massive elements = 1:1 heavier elements = ~3:2However, the nuclei of any isotopes that differ much from these ratios are unstable and therefore are radioactive.

RadioactivityGot My Eye on Ions! Lab

Given a substance in which the number of protons, neutrons, and electrons are known, how could it be determined if it is an electrical stable atom, or isotope, or an ion?

Create data table. Bag numbers=1-14Bag Number

Number of Protons (brown)

Number of Neutrons (white)

Number of Electrons (lentils)

Ion, Isotope or electrically stable element?

Name of Bag’s Element

12

Do NOW:Discuss with you elbow partner:

Is the song Radioactive by Imagine Dragons properly titled? Justify your response.

Homework• Due Monday, Nov. 16—Experiment

and data collection ends• Due Wednesday, Nov. 18—data

tables and graph(s)• Due Friday, Nov. 20—conclusion due

Georgia Performance StandardsSPS3. Students will distinguish the characteristics

and components of radioactivity.a. Differentiate among alpha and beta particles and gamma radiation.b. Differentiate between fission and fusion.c. Explain the process half-life as related to radioactive decay.d. Describe nuclear energy, its practical application as an alternative energy, and its potential problems.

The Big Idea: Nuclear Decay

Essential Question:Why is it important to know that nuclear decay produces nuclear

radiation?

HomeworkBring one individualized size bag of M&M’s for activity on Tuesday.

Discuss the Great Debate—receive role cards. Prepare for your role for the debate on Friday.

Nuclear DecayIn 1896, Henri Becquerel left Uranium salt in a drawer. Later he found the outline of clumps it leading him to hypothesize that it emitted radiation.

In 1899, Ernest Rutherford discovered that U compounds produce 3 kinds of radiation: alpha, beta, and gamma

https://www.khanacademy.org/science/chemistry/radioactive-decay/v/types-of-decay

Nuclear DecayAlpha Particles—made of 2 protons and 2 neutronsMore massive than beta or gamma with the most electric charge

Can be stopped by a sheet of paper.

Alpha Particles

SymbolMass 4Charge

+2

Damage and Uses of Alpha ParticlesIf released in human body, can damage biological molecules causing illness and disease.

Smoke detectors give off alpha particles that ionize surrounding air, if smoke enters the ionized air the alarm goes off.

Transmutation—the process of changing one element to another through nuclear decay.

Nuclear Decay

Beta ParticlesIn an unstable nucleus a neutron decays into a proton and emits an electron

The emitted electron from the nucleus is the beta particle; however, the mass number stays the same

Nuclear Decay

Beta Particles

+Symbol 0e

__1

Mass 0.0005Charge __1

Nuclear DecayDamage and uses of Beta Particles

Pass through paper but stopped by aluminum foil

Damage cells when emitted by radioactive nuclei in side the human body.

Gamma RaysElectromagnetic waves with the highest frequencies and shortest wavelengths

No mass and no chargeTravel at the speed of lightEmitted when alpha decay or beta decay occurs

Nuclear Decay

Gamma Rays

SymbolMass 0Charge 0

Nuclear DecayDamage from Gamma Rays

Thick blocks of dense materials (i.e.: concrete or lead)are required to stop gamma rays

Cause less damage to biological molecules as they pass through living tissue.

Gamma rays produce fewer ions because it has no electric charge

Do NOW:Get out your M&M’s packet—put them to the side

Georgia Performance StandardsSPS3. Students will distinguish the characteristics

and components of radioactivity.a. Differentiate among alpha and beta particles and gamma radiation.b. Differentiate between fission and fusion.c. Explain the process half-life as related to radioactive decay.d. Describe nuclear energy, its practical application as an alternative energy, and its potential problems.

The Big Idea: Radioactive Half-Life

Essential Question:What is a daughter nucleus?

Radioactive Half-LifeHalf-Life—length of time it takes ½ of the atoms of a sample of the isotope to decaycan be seconds to years

The nucleus left after the isotope decays is called the daughter nucleus.http://www.brainpop.com/technology/scienceandindustry/carbondating/

Radioactive Half-LifeThe amounts of a radioactive isotope and its daughter nucleus are needed to date materials.

Sample Half-LivesIsotope Half-Life

3 H 1 12.3 years

212 Pb 82 10.6 years

14C 6 5,730 years

211Po 84 0.5 s

235 U 92

7.04 X 108 years

131 I 53 8.04 days

https://www.khanacademy.org/science/chemistry/radioactive-decay/v/half-life

Radioactive Half-LifePurpose: To determine the half-life of the

element M & Mium. **Radioactive members of this isotope family are easily distinguished via a bold M on the front surface of the atom.**Materials:

Individualized size bag of M & Mium Isotopes

One plastic cup

Radioactive Half-LifeProcedure:1. Count the number of M & Mium atoms as

you place them in the cup. Record the total number of radioactive atoms you start with in your data table (on the back of your graph paper).

2. Cover and shake/rattle the cup.

Radioactive Half-LifeProcedure:3. Carefully pour your atoms onto your

white paper. You will see that several of the previously radioactive atoms in the group have decayed, and the m is no longer visible. This means that they are now considered "safe" and, since they are no longer radioactive, may actually be eaten without fear of any harm to you!

Radioactive Half-LifeProcedure:3. conti: Please do so, and as you remove

the edible atoms, count them so you may determine the number of atoms that have decayed in that particular shake.

4. Now you need to continue this pattern until no more radioactive members remain. Remember to record the number of decayed atoms after each shake!

Radioactive Half-LifeData Table: Trial

(1-14)# Undecayed (Radioactive)

1234567

Radioactive Half-LifeAnalysis:

Using the graph paper provided, construct a graph by plotting the number of half lives as the independent variable (x-axis) and the number of un-decayed atoms as the dependent variable (y-axis). Remember to label you x-axis, y-axis, and indicate a title for your graph.

Radioactive Half-LifeQuestions:1. In your lab experience, you stopped when

you reached zero un-decayed isotopes. How accurate is this when talking about half-lives?

2. Do you think your graph would have been different if you had started with more pieces of candy, for example 500 or 1000? Explain.

3. Assume that each trial took 30 seconds. Based on your results, what is the half-life of M & Mium?

Radioactive Half-LifeThe value for the half-life is obtained as follows:

Select two values on the y-axis. One value should be twice as large as the other (i.e.: 60 & 30)

Draw lines from these points to your line.Next, vertical lines should be drawn from where these lines intersect your lines to the x-axis. The space between these lines on the x-axis is the half-life.

Do NOW:

Discuss with your table group the difference in fusion and fission.

Georgia Performance StandardsSPS3. Students will distinguish the characteristics

and components of radioactivity.a. Differentiate among alpha and beta particles and gamma radiation.b. Differentiate between fission and fusion.c. Explain the process half-life as related to radioactive decay.d. Describe nuclear energy, its practical application as an alternative energy, and its potential problems.

The Big Idea: Nuclear Reactions

Essential Question:Why is nuclear fusion safer for the environment than nuclear fission?

Nuclear ReactionsNuclear Fission Fission means

division splitting a large

nucleus into two or more smaller nuclei; energy is released

how nuclear power plants operate

Nuclear ReactionsNuclear Fusion 2 nuclei w/ low masses are combined to

form 1 nucleus w/ larger mass Only at temps of millions of 0C can

fusion occur happens in stars how sun operates

Watch video http://www.youtube.com/watch?v=ppJ5TB2-MUQ

Nuclear ReactionsChain reaction series of

repeated fission reactions

caused by the release of neutrons in each reaction

Nuclear ReactionsUsing Nuclear Reactions Radioactive isotopes can be located

by detecting the radiation they emit. Treatment of cancer Tracer—a radioisotope used to find or

keep track of molecules in an organism

examples: carbon-11, iodine-131 and sodium-24

doctors use it to monitor organ functions

in agriculture to monitor uptake of nutrients and fertilizers

Nuclear ReactionsRadioactivity Nuclear

ReactionsAdvantages Advantages

Disadvantages Disadvantages

Using your textbook make a t-chart as indicated to the right.

Do NOW:3 Facts and a Fib• Write 4 statements about nuclear fission

and fusion. 3 should be facts; 1 should be a fib (wives tail)

Georgia Performance StandardsSPS3. Students will distinguish the characteristics

and components of radioactivity.a. Differentiate among alpha and beta particles and gamma radiation.b. Differentiate between fission and fusion.c. Explain the process half-life as related to radioactive decay.d. Describe nuclear energy, its practical application as an alternative energy, and its potential problems.

The Big Idea: Nuclear Energy

Essential Question:How can nuclear energy be used to

produce energy to help reduce the use of fossil fuels?

Nuclear EnergyAbout 20% of electricity in US comes from nuclear power plants

Nuclear reactors-have fuel, rods, and cooling system

Heat is made when fission-energy is released

Rods absorb neutrons to prevent dangerous chain reactions

Nuclear EnergyHow nuclear power plants work:use heat from Uranium isotope fission as steam

steam drives a turbineturbine rotates a generator

Nuclear EnergyPros to Nuclear energy:produces no smokecarbon-free produces more electricity than other renewables (like solar & wind)

cheaper to producemore reliable

Nuclear EnergyPros to Nuclear energy:3rd world countries can utilize no global warming association used to irradiate food to kill bacteria to preserve food longer

Nuclear EnergyCons to Nuclear energy:nuclear waste- radioactive by-products

from radioactive materials high-level waste: dispose carefully b/c it

remains radioactive for tens of 1000 of years

environmental dangers from mining, warm water, radiation leakage

health concerns-cancers, death