Science 10. Unit 4:Physics. Block: Name: Book 3: radioactivty

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1 Science 10 Unit 4:Physics Book 3: radioactivty Name: Block: 1

of with a mass of. So, it has protons and neutrons.

2 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: U Practice: Write the following isotopes in standard atomic notation. potassium-39 potassium-41 2

3 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: I Xe β 3

The sum of the cannot change: the total number of protons in the parent and daughter isotopes, and decay products must be equal.

4 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: 4

5 Example: Write an equation for the alpha decay of uranium-238. STEPS: 1. Write the parent isotope in SAN 2. Put an arrow after the parent isotope 3. Complete the daughter isotope as follows: decrease the atomic number of the parent isotope by 2 and the decrease the atomic mass by 4. Then, find the new element that you have created on the periodic table (based on the atomic number), and add the symbol. 4. For the other product, add an alpha particle in SAN 5. Make sure that atomic masses and atomic numbers are balanced. 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 SAN 2. Put an arrow after the parent isotope 3. Complete the daughter isotope as follows: increase the atomic number of the parent isotope by 1. Leave the mass number unchanged. Then, find the new element that you have created on the periodic table (based on the atomic number), and add the symbol. 4. For the other product, add a beta particle in SAN 5. Make sure that atomic masses and atomic numbers are balanced. 5

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

Summary Symbol Description Mass Charge Penetration STEPS: 1. Write the parent isotope in SAN. Use an asterisk to denote that it is high energy. 2. Put an arrow after the parent isotope 3.

6 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 Symbol Description Mass Charge Penetration STEPS: 1. Write the parent isotope in SAN. Use an asterisk to denote that it is high energy. 2. Put an arrow after the parent isotope 3. Complete the daughter isotope as follows: keep it the same as the parent isotope (but no asterisk). 4. For the other product, add a gamma particle in SAN 5. Make sure that atomic masses and atomic numbers are balanced. Alpha Beta Gamma Look at your Data Page: 6

7 Assignment #5.1: Complete the following worksheet in the space provided below Part 1 Complete the table below. Isotope Name Atomic Number Mass Number Number of Protons Number of Neutrons carbon-14 carbon lithium neon 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 7

8 Part 3 Identify the following nuclear decay reactions as either alpha decay (AD), beta decay (BD), gamma decay (GD): Reaction Decay Type Ac Fr α Sm Eu ββ Pa Ac He Ni 0 60 γγ Ni F Ne Fe 58 Fe Na F Part 4 Complete the following alpha decay reactions. Reaction Po α Fr At Fr α Part 5 Complete the following beta decay reactions. Reaction Co ββ C ββ I 0 1 e + 8

9 Part 6 Complete the following gamma decay reactions. Reaction Gd γ Cf γ Mg γ Part 7 Complete the following decay reactions. Reaction Pa He Dy γ Ra α Po ββ Ar γ Th He e Pb ββ Tl Bi He Pa γ Mg e 9

) Others decay at a rate and have half-lives Example: Astatine-213 =125 nanoseconds) Graphing Radioactive Decay

10 5.2 : Half-life & Radioactive Dating 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 100 Half-lives Amount Remaining Amount remaining (%) Half-lives 10

that dating becomes Radioactive Dating: potassium-40 Clock When cools it contains a certain amount of radioactive Over time the potassium-40 into, with

11 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 11

12 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 halflife and time, and at for the amount of the parent isotope Half-Life Time Amount % Practice: If 50 grams of carbon-14 were present in a sample of bone, state how many grams would be left after years? Half-life Time (years) Mass (g) 12

13 Assignment #5.2: Complete the following worksheet in the space provided below Part 1 Complete the following tables. Half-life 0 Percent of parent isotope Percent of daughter isotope Half-life 0 Fraction of parent isotope Fraction of daughter isotope 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 5 years. Complete the following table. Half-life Time (years) Mass (g) 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 original parent isotope would remain after the first 12 minutes? 13

14 3. The half-life of a particular radioactive isotope is 8 hours. What percent of the parent isotope would remain after 1 day? 4. A radioactive isotope sample has a half-life of 4 days. If 6 g of the sample remains unchanged after 12 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 parent isotope 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 later found 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 original count. 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-90 will be present in the soil 84 years later? 14

5.3 : Nuclear Reactions 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

15 5.3 : Nuclear Reactions 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 15

16 Practice: Complete the following nuclear fission reaction: 1 0 n U Mo n Complete the following nuclear fusion reaction: 2 1 H H n The Benefits of Using Nuclear Reactions Fission reactions are used around the world inside of, generating without combustion or CO 2, 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 16

radiation were released This caused many devastating and - term effects, including and

17 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 17

18 Assignment #5.3: Complete the following worksheet in the space provided below Identify each of the following nuclear reactions as either fission (FI), or fusion (FU), and then complete the reaction. Reaction Reaction Type n U n Xe H H 1 0 n U n Ba n Ba n n Cs Rb n U Xe n H H 1 0 n n U n Ge H Li n n Xe n Pd n U n I H H He n U n In n Te n Mo n Cl H 18

Physics (Part 2) Unit Review Package Vocabulary: Referring to your notes and textbook, define each of the following vocabulary terms in a complete

19 Physics (Part 2) Unit Review Package 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 19

20 Knowledge: Write the following isotopes in standard atomic notation. 10. cobalt barium sodium zinc americium hydrogen Complete the following table describing the three types of radiation: Symbol Alpha Beta Gamma 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) Hg Tl β 1 0 n U Tn Mo n Ac Fr α Pa He Ac Na 0 1 e Mg Ni* Ni γ 1 0 n U Kr n Ba 2 1 H Li 7 4 Be n 20

21 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 U He Na e n U n Se K β He γ He Mg Sc α n U Zr n n U n Pd 21

35. Describe the disadvantages and advantages of using fission reactions to generate electricity. 36. At right is the decay curve for potassium-40 and its daughter isotope argon-40.

22 35. Describe the disadvantages and advantages of using fission reactions to generate electricity. 36. At right is the decay curve for potassium-40 and its daughter isotope argon-40. You analyse a sample of volcanic rock and find 10% potassium-40 compared to 90% argon-40. How long ago were these rocks formed? Explain your answer. 37. If a rock originally contains 100 g of a radioactive isotope, 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 be left after 2000 years? Show your work. 22

23 39. If a rock has only 20 g of radioactive isotope remaining after 3 half-lives, how much was there to start with? Show your work. 40. Carbon-14 has a half-life of 5730 years. How much of an original sample weighing 80 g would be left 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 sample originally weighed 200 kg, and is now 2.6 billion years old, identify its half-life and the parent isotope. Show your work. 23

Radioactivity Review (Chapter 7)

Science 10 Radioactivity Review (Chapter 7) 1. The alpha decay of radon-222 will yield which of the following? a. bismuth-220 c. astatine-222 b. francium-222 d. polonium-218 2. Which of the following types