Chapter 19a. Radioactivity and Nuclear Energy

Transcription

1 Chapter 19a Radioactivity and Nuclear Energy

2 Chapter 19 Table of Contents 19.1 Radioactive Decay 19.2 Nuclear Transformations 19.3 Detection of Radioactivity and the Concept of Half-life 19.4 Dating by Radioactivity 19.5 Medical Applications of Radioactivity Copyright Cengage Learning. All rights reserved 2

3 Section 19.1 Radioactive Decay Review 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 A X Z Copyright Cengage Learning. All rights reserved 3

4 Section 19.1 Radioactive Decay Radioactive Decay radioactive nucleus which spontaneously decomposes forming a different nucleus and producing one or more particles nuclear equation shows the radioactive decomposition of an element Paper Wood Lead Copyright Cengage Learning. All rights reserved 4

5 Section 19.1 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. Copyright Cengage Learning. All rights reserved 5

6 Section 19.1 Radioactive Decay Types of Radioactive Decay Beta Particle Production Beta particle electron Examples Net effect is to change a neutron to a proton. Copyright Cengage Learning. All rights reserved 6

7 Section 19.1 Radioactive Decay Types of Radioactive Decay Gamma Ray Release Gamma ray high energy photon Example Net effect is no change in mass number or atomic number. Copyright Cengage Learning. All rights reserved 7

8 Section 19.1 Radioactive Decay Types of Radioactive Decay Positron Production Positron particle with same mass as an electron but with a positive charge Example Net effect is to change a proton to a neutron. Copyright Cengage Learning. All rights reserved 8

9 Section 19.1 Radioactive Decay Types of Radioactive Decay Electron Capture Process in which one of the inner-orbital electrons is captured by the nucleus. Example Copyright Cengage Learning. All rights reserved 9

10 Section 19.1 Radioactive Decay Various Types of Radioactive Processes Copyright Cengage Learning. All rights reserved 10

11 Section 19.1 Radioactive Decay Decay Series Occurs until a stable nuclide is formed. Copyright Cengage Learning. All rights reserved 11

12 Section 19.1 Radioactive Decay Concept Check Which of the following produces a particle? a) Ga + e Zn b) Cu e + Ni c) Fr He + At d) Sb e + Te electron capture positron alpha particle beta particle Copyright Cengage Learning. All rights reserved 12

13 Section 19.2 Nuclear Transformations Change of one element to another Bombard elements with particles Examples Copyright Cengage Learning. All rights reserved 13

14 Section 19.2 Nuclear Transformations Transuranium Elements Elements with atomic numbers greater than 92 which have been synthesized. Copyright Cengage Learning. All rights reserved 14

15 Section 19.2 Nuclear Transformations Concept Check 243 Am 95 If the bombardment of with alpha particles leads to the emission of a neutron, which nuclide is formed in this nuclear transformation process? a) Bk b) Cm c) Cm d) Bk Copyright Cengage Learning. All rights reserved 15

16 Section 19.3 Detection of Radioactivity and the Concept of Half-life Geiger Mϋller Counter Instrument which measures radioactive decay by registering the ions and electrons produced as a radioactive particle passes through a gas-filled chamber. Copyright Cengage Learning. All rights reserved 16

17 Section 19.3 Detection of Radioactivity and the Concept of Half-life Scintillation Counter Instrument which measures the rate of radioactive decay by sensing flashes of light that the radiation produces in the detector. Copyright Cengage Learning. All rights reserved 17

18 Section 19.3 Detection of Radioactivity and the Concept of Half-life Discovery of Po and Ra Marie Skłodowska Curie ( ) Marie, and her husband Pierre, analyzed a ton of Uranium ore. After removing the uranium the radioactivity increased. This led to the discovery of Polonium, more radioactive than uranium, named after here home country of Poland. After removing the Polonium the radioactivity increased again. This led to the discovery of a small amount in their hand of Radium, so radioactive that it glowed in the dark. Copyright Cengage Learning. All rights reserved 18

19 Section 19.3 Detection of Radioactivity and the Concept of Half-life Half-life Time required for half of the original sample of radioactive nuclides to decay. Copyright Cengage Learning. All rights reserved 19

20 Section 19.3 Detection of Radioactivity and the Concept of Half-life Concept Check Strontium-90 is a by-product of nuclear fission and a contaminant associated with the testing of nuclear weapons. It is of particular concern to humans because it tends to become concentrated in bones, substituting for calcium (similar ionic radius and both 2+ ionic charge). The half-life of 38Sr is 29 years. If milk contaminated with 38Sr is 90 ingested, after 58 years what percentage of the 38Sr replacing Ca in bones would remain to continue emitting beta particles? a) 100% b) 75% c) 50% d) 25% Copyright Cengage Learning. All rights reserved 20

21 Section 19.4 Dating by Radioactivity Radiocarbon Dating (Carbon-14 Dating) Originated in 1940s by Willard Libby Based on the radioactivity of carbon-14 Used to date wood and artifacts Copyright Cengage Learning. All rights reserved 21

22 Section 19.5 Medical Applications of Radioactivity Radiotracers Radioactive nuclides that can be introduced into organisms and traced for diagnostic purposes. Copyright Cengage Learning. All rights reserved 22

23 Section 19.5 Medical Applications of Radioactivity Radon A rare noble gas which has also been implicated as a possible cause of lung cancer. Accumulates in houses from particular kinds of soils or rock strata. 15- Copyright Cengage Learning. All rights reserved 23

24 Section 19.5 Predicted Medical Applications Indoor Radon of Levels Radioactivity red zones-greater than 4 pci/l orange zones-between 2 and 4 pci/l yellow zones-less than 2 pci/l Santa Barbara/ Ventura Counties highest levels 15- Copyright Cengage Learning. All rights reserved 24

25 W Section 19.5 Medical Applications of Radioactivity Chapter 19b Radioactivity and Nuclear Energy Copyright Cengage Learning. All rights reserved 25

26 Section 19.5 Predicted Medical Indoor Applications Radon Levels of Radioactivity 19.6 Nuclear Energy 19.7 Nuclear Fission 19.8 Nuclear Reactors 19.9 Nuclear Fusion Effects of Radiation Copyright Cengage Learning. All rights reserved 26

27 Section 19.6 Nuclear Energy Two types of nuclear processes can produce energy. Combining two light nuclei to form a heavier nucleus - fusion Splitting a heavy nucleus into two nuclei with smaller mass numbers - fission Iron has the most stable nucleus Copyright Cengage Learning. All rights reserved 27

28 Section 19.7 Nuclear Fission Releases J/mol of uranium-235 Each fission produces 3 neutrons. Copyright Cengage Learning. All rights reserved 28

29 Section 19.7 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 Copyright Cengage Learning. All rights reserved 29

30 Section 19.7 Nuclear Fission A Schematic Diagram of a Nuclear Power Plant Copyright Cengage Learning. All rights reserved 30

31 Section 19.7 Nuclear Fission Nuclear energy generates about 21 percent of the electricity produced in the United States. Questions of safety, costs, and nuclear waste disposal have halted construction of nuclear reactors in the United States. Copyright Cengage Learning. All rights reserved 31

32 Section 19.7 Nuclear Fission Nuclear Power plants locations throughout the world. Copyright Cengage Learning. All rights reserved 32

33 Section 19.7 Nuclear Fission Disposal of Radioactive Waste Where can you dispose of radioactive waste where it will be safe? In the ground as shown to the right? Into space? Into the Sun? Copyright Cengage Learning. All rights reserved 33

34 Section 19.7 Nuclear Fission Plutonium When nonfissionable U-238 captures a fast neutron, it eventually forms the fissionable nuclide of plutonium, Pu-239, which can support a chain reaction. Plutonium is a transuranium element, meaning that it has an atomic number greater than the 92 of uranium. The fissionable plutonium produced in a uranium-fueled reactor can be used as a fuel or in nuclear weapons. Little Boy Fatman Copyright Cengage Learning. All rights reserved 34

35 Section 19.7 Nuclear Fission Nuclear Bombs Hiroshima Equivalent to kilotons of TNT Trinity Bomb /trinity_nuclear_weapon_test/ Copyright Cengage Learning. All rights reserved 35

36 Section 19.7 Nuclear Fission Hiroshima 70,000 killed immediately and 70,000 more later. Half from blast, a third radiation and rest from radioactivity. Imprint of sitting person Copyright Cengage Learning. All rights reserved 36

37 Section 19.7 Nuclear Fission Nagasaki Equivalent to kilotons of TNT Compare to the Tsar Bomb dropped in 1961 that was equivalent to 51 megatons of TNT or 50,000 kt of TNT. Copyright Cengage Learning. All rights reserved 37

38 Section 19.7 Nuclear Fusion Fission Process of combining 2 light nuclei Produces more energy per mole than fission Powers the stars and sun Copyright Cengage Learning. All rights reserved 38

39 Section 19.7 Nuclear Fusion Fission Requires extremely high temperatures Currently not technically possible for us to use as an energy source Copyright Cengage Learning. All rights reserved 39

40 Section 19.7 Nuclear Fusion Fission Nuclear fusion produces tremendous quantities of energy and has the potential of becoming the ultimate source of energy on earth. Copyright Cengage Learning. All rights reserved 40

41 Section 19.7 Nuclear Fission Biological Effects of Radiation Depend on: 1. Energy of the radiation 2. Penetrating ability of the radiation 3. Ionizing ability of the radiation 4. Chemical properties of the radiation source Copyright Cengage Learning. All rights reserved 41

42 Section 19.7 Nuclear Fission Effects of Short Term Exposures to Radiation Copyright Cengage Learning. All rights reserved 42

43 Section 19.7 Nuclear Fission Typical Radiation Exposures for a Person Living in the U.S. Copyright Cengage Learning. All rights reserved 43