June 01, Chapter 19 SMARTBOARD Notes.notebook. Objectives

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another by particle bombardment To learn

1 Objectives To learn the types of radioactive decay To learn to write nuclear equations for radioactive decay To learn how one element may be changed to another by particle bombardment To learn about radiation detection instruments To understand half life 1

2 A Review of Atomic Terms Nucleons particles found in the nucleus of an atom > neutrons > protons Atomic Number (Z) number of protons in the nucleus Mass Number (A) sum of the number of protons and neutrons Isotopes atoms with identical atomic numbers but different mass numbers Nuclide each unique atom Isotope review activity 2

3 A. Radioactive Decay Radioactivity the spontaneous decomposition of a nucleus forming a different nucleus and producing one or more additional particles Nuclear Equation shows the radioactive decomposition of an element 14 6C 14 7N + 0 1e Nuclear Forces strong nuclear force holds neutrons and protons together to form a nucleus (counters electromagnetic repulsion). Weak nuclear force operates within individual nucleons and gives rise to some kinds of radioactivity Strong and Weak Nuclear Forces 3

4 4

5 Standard Model 5

6 Discovery of Radioactivity Antoine Henri Becquerel ( ) Noticed the fogging of photographic plate by uranium crystals Pierre Curie ( ), Marie Curie ( ) Further studies of uranium and discovery of polonium and radium. Marie received two Nobel prizes. She died from the effects of radiation doses received during her experiments Ernest Rutherford ( ) His understanding of atomic structure helped us understand the role of the nucleus. He defined many of the terms used to discuss radioactivity today Discovery Discovery 2 Discovery 3 6

7 A. Radioactive Decay Types of Radioactive Decay Alpha particle production > Alpha particle helium nucleus > Examples > Net effect is loss of 4 in mass number and loss of 2 in atomic number. 7

8 A. Radioactive Decay Types of Radioactive Decay Beta particle production > Beta particle electron > Examples > Net effect is to change a neutron to a proton. 8

9 A. Radioactive Decay Types of Radioactive Decay Gamma ray release > Gamma ray high energy photon > Examples > Net effect is no change in mass number or atomic number. 9

10 A. Radioactive Decay Types of Radioactive Decay Positron production > Positron particle with same mass as an electron but with a positive charge (antimatter version of an electron) > Examples > Net effect is to change a proton to a neutron. 10

11 A. Radioactive Decay Types of Radioactive Decay Electron capture Inner orbital electron is captured. New nucleus formed. Neutrino and gamma ray produced Hg + 0 1e Au + ν + 0 0γ > Net effect is to change a proton to a neutron 11

12 A. Radioactive Decay Conservation of Mass Number and Charge Number both are retained in a nuclear reaction sum of both from the reactants and products are constant 12

13 Band of Stability Black squares indicate stable nuclei. Decay occurs to move isotopes towards the black line 13

14 A. Decay Series Decay series activity 14

15 B. Nuclear Transformations Nuclear Transformation forced change of one element to another Bombard elements with particles 15

16 Transuranium elements elements with atomic numbers greater than 92 which have been synthesized UUO 16

17 C. Detection of Radioactivity and the Concept of Halflife Geiger Muller counter instrument which measures radioactive decay by registering the ions and electrons produced as a radioactive particle passes through a gasfilled chamber 17

18 C. Detection of Radioactivity and the Concept of Halflife Scintillation counter instrument which measures the rate of radioactive decay by sensing flashes of light that the radiation produces in the detector 18

19 C. Detection of Radioactivity and the Concept of Halflife Half life time required for half of the original sample of radioactive nuclides to decay 19

20 Decay of a Radioactive Element Half of the radioactive parent atoms decay after one half life. Half of the remainder decay after another half life and so on.. Half life activity 20

21 Half Life Calculations For a radioactive decay, Time passed, Half life, Initial mass and Final mass can be calculated using the following formula: initial mass = final mass x 2 (elapsed time/half life) 21

22 Objectives To learn about some uses of radioactivity in our lives 22

23 Some Uses Of Radioactivity Food Sterilization Medical Applications and Radiotracers Smoke detectors Radiocarbon Dating (Energy Production) (Weapons) 23

24 Food Sterilization Gamma irradiation of foods often from 60 Co source Spices, herbs and dehydrated vegetables. Also pork and poultry FDA approved 24

25 Medical Applications of Radioactivity Radiotracers Radioactive nuclides can be introduced into laboratory reactions or organisms and traced for diagnostic purposes. 25

26 Medical Applications of Radioactivity Scanners Medical Scanners utilize many types of radiations X Rays Bone structures opaque to rays X ray computed tomography (CT Scan X rays) Magnetic Resonance Imaging (MRI Nuclear magnetism) Ultrasound (high frequency sound waves) Positron Emission Tomography (PET Scan) > Positron emitting tracer into body, concentrates in organ of interest > Positrons annihilate with electron giving off pairs of gamma rays > Detector maps pair to show image of organ 26

current to flow Smoke absorbs alpha particles,

27 Smoke Detectors Americium 241 emits alpha particles and ionizes air in a space in the detector Ions allow a current to flow Smoke absorbs alpha particles, interferes with ion formation and electric current. An alarm sounds 27

28 Dating by Radioactivity Radiocarbon dating Originated in 1940s by Willard Libby Based on the radioactivity of carbon 14 Used to date wood and artifacts up to about 50,000 years old Radiocarbon dating activity 28

29 Objectives To introduce fusion and fission as sources of energy To learn about nuclear fission To understand how a nuclear reactor works To learn about nuclear fusion To understand nuclear weapons To see how radiation damages human tissue 29

A. Nuclear Energy Two types of nuclear processes can produce energy Combining 2 light nuclei to form a heavier nucleus fusion Splitting a heavy nucleus into

30 A. Nuclear Energy Two types of nuclear processes can produce energy Combining 2 light nuclei to form a heavier nucleus fusion Splitting a heavy nucleus into 2 nuclei with smaller mass numbers fission Energy produced by conversion of mass, E = mc 2 Sun converts 4 million tonnes per second Fusion and Fission POGIL 30

31 B. Nuclear Fission Each atomic fission produces 3 neutrons Releases 2.1 x J/mol uranium 235 (Burning methane produces 8.90 x 10 5 J/mol) 31

32 B. Nuclear Fission Chain reaction self sustaining fission process caused by the production of neutrons that proceed to split other nuclei Critical mass mass of fissionable material required to produce a chain reaction Chain Reaction Alternative CR 32

33 C. Nuclear Reactors 33

34 C. Nuclear Reactors Reactor core Nuclear Power Plants 34

35 B. Nuclear Fission The Battle Of Chernobyl Chernobyl 1 Chernobyl 2 Chernobyl 3 Nuclear Energy in the US? 35

36 Nuclear Power Plants in the NJ Area 36

37 D. Nuclear Fusion Process of combining two light nuclei Produces more energy per mole than fission Powers the stars and sun 37

D. Nuclear Fusion Atoms lighter than Fe.

power source issues with confinement Used

38 D. Nuclear Fusion Atoms lighter than Fe. Deuterium used Requires extremely high temperatures > 100 million o K Currently not technically possible for use as a power source issues with confinement Used as Hydrogen bomb Sun s energy captured for our use 38

39 Nuclear Binding Energy Binding Energy 39

produced in bomb Limited up to 500 kilotons of

40 Nuclear Weapons Fission Weapons ( Atomic Bombs ) Enriched uranium or plutonium Supercritical mass produced in bomb Limited up to 500 kilotons of TNT Twice used in warfare (Hiroshima and Nagasaki) 40

Nuclear Weapons Fusion Weapons ( Thermonuclear / Hydrogen Bombs ) deuterium and tritium fission bomb compresses and heats hydrogen fuel further

41 Nuclear Weapons Fusion Weapons ( Thermonuclear / Hydrogen Bombs ) deuterium and tritium fission bomb compresses and heats hydrogen fuel further stages of fission reactions (depleted uranium) largest so far is 57 megatons ( Tsar Bomba USSR) Radioactive fallout can be regulated salted, neutron bomb 41

entry Vehicles Tactical weapons: shells, torpedoes Strategy Cold War, Arms

42 Nuclear Weapons Now I am become Death, the destroyer of worlds Delivery Gravity bombs Missiles (land or submarine launch) Multiple Independent Re entry Vehicles Tactical weapons: shells, torpedoes Strategy Cold War, Arms Race Mutually Assured Destruction Missile Defense Terrorist Threat WWII

Nuclear Weapons Regulation UN, International Atomic Energy Agency Test Ban and Nuclear Non Proliferation Treaties SALT s and START s (limitation and reduction) Still enough to destroy most human

43 Nuclear Weapons Regulation UN, International Atomic Energy Agency Test Ban and Nuclear Non Proliferation Treaties SALT s and START s (limitation and reduction) Still enough to destroy most human life on Earth (23,000 bombs equivalent to 150,000 Hiroshima bombs) US, Russia, China, UK, France, India, Pakistan, North Korea, Israel (?), South Africa (X) Obama ( World without nuclear weapons ) 43

E. Effects of Radiation Factors Determining Biological Effects of Radiation Energy of the radiation Penetrating ability of the radiation Ionizing ability of the radiation Cell repair, death (high

44 E. Effects of Radiation Factors Determining Biological Effects of Radiation Energy of the radiation Penetrating ability of the radiation Ionizing ability of the radiation Cell repair, death (high dose / acute damage), incorrect repair (low dose / cancer) Chemical properties of the radiation source Strontium 90 and Radium 226 behave similarly to calcium so tend to accumulate in bones. Radioactive Iodine concentrates in the thyroid 44

45 Penetrating Ability of Radiation Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. Beta radiation, consisting of electrons or positrons, is halted by an aluminum plate. Gamma radiation is dampened by lead 45

46 E. Effects of Radiation Rem: the quantity of ionizing radiation whose biological effect is equal to that produced by one roentgen of x rays. Roentgen is a defined amount of ionization of dry air 46

47 U.S.Nuclear Regulatory Commission limit of 5,000 mrem/year above background for nuclear industry workers 47

48 48

Ch 17 Radioactivity & Nuc. Chemistry Study Guide Accelerated Chemistry SCANTRON

Ch 17 Radioactivity & Nuc. Chemistry Study Guide Accelerated Chemistry SCANTRON Name No-Calculators Allowed /65 MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers