Chapter 19a Radioactivity and Nuclear Energy

Chapter 19 Table of Contents Radioactive Decay 19.2 Nuclear Transformations 19.3 Detection of Radioactivity and the Concept of Half-life 19.4Dating by Radioactivity 19.5Medical Applications of Radioactivity

Section 19.1 Radioactive Decay Return to TOC 3 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

Section 19.1 Radioactive Decay Return to TOC 4 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

Section 19.1 Radioactive Decay Return to TOC 5 Various Types of Radioactive Processes

Section 19.1 Radioactive Decay Return to TOC Copyright © Cengage Learning. All rights reserved 6 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. Mainly occurs in elements of atomic number 80 or higher.

Section 19.1 Radioactive Decay Return to TOC Copyright © Cengage Learning. All rights reserved 7 Types of Radioactive Decay – Beta Particle Production Beta particle – electron  Examples Net effect is to change a neutron to a proton.

Section 19.1 Radioactive Decay Return to TOC Copyright © Cengage Learning. All rights reserved 8 Types of Radioactive Decay – Gamma Ray Release Gamma ray – high energy photon  Example Net effect is no change in mass number or atomic number.

Section 19.1 Radioactive Decay Return to TOC Copyright © Cengage Learning. All rights reserved 9 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.

Section 19.1 Radioactive Decay Return to TOC Copyright © Cengage Learning. All rights reserved 10 Types of Radioactive Decay – Electron Capture Process in which one of the inner-orbital electrons is captured by the nucleus to change a proton into a neutron.  Example

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

Section 19.1 Radioactive Decay Return to TOC Copyright © Cengage Learning. All rights reserved 12 Concept Check Which of the following produces a particle? electron capture positron alpha particle beta particle

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

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

Section 19.2 Return to TOC Nuclear Transformations Copyright © Cengage Learning. All rights reserved 15 Concept Check If the bombardment of with alpha particles leads to the emission of a neutron, which nuclide is formed in this nuclear transformation process? Am He Bk n

Section 19.3 Return to TOC Detection of Radioactivity and the Concept of Half-life 16 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.

Section 19.3 Return to TOC Detection of Radioactivity and the Concept of Half-life 17 Scintillation Counter Instrument which measures the rate of radioactive decay by sensing flashes of light that the radiation produces in the detector.

Section 19.3 Return to TOC Detection of Radioactivity and the Concept of Half-life 18 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. (1943 Marie Currie Movie 2hrs)

Section 19.3 Return to TOC Detection of Radioactivity and the Concept of Half-life 19 Half-life Time required for half of the original sample of radioactive nuclides to decay.

Section 19.3 Return to TOC Detection of Radioactivity and the Concept of Half-life Copyright © Cengage Learning. All rights reserved 20 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 is 29 years. If milk contaminated with is ingested, after 58 years what percentage of the replacing Ca in bones would remain to continue emitting beta particles? a)100% b)75% c)50% d)25%

Section 19.4 Dating by Radioactivity Return to TOC 21 Radiocarbon Dating (Carbon-14 Dating) Originated in 1940s by Willard Libby  Based on the radioactivity of carbon-14 Used to date wood and artifacts

Section 19.4 Dating by Radioactivity Return to TOC 22 Potassium Argon Dating The ratio of remaining K and Ar gas formed can indicate the age of solidified lava rock. Calibration is impossible.

Section 19.5 Medical Applications of Radioactivity Return to TOC 23 Radiotracers Radioactive nuclides that can be introduced into organisms and traced for diagnostic purposes.

Section 19.5 Medical Applications of Radioactivity Return to TOC 24 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-

Section 19.5 Medical Applications of Radioactivity Return to TOC 25 Predicted Indoor Radon Levels 15- 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

Section 19.5 Medical Applications of Radioactivity Return to TOC 15- Preventing Radon in Homes

Section 19.5 Medical Applications of Radioactivity Return to TOC 27 Chapter 19b Radioactivity and Nuclear Energy W

Section 19.5 Medical Applications of Radioactivity Return to TOC Nuclear Energy 19.7Nuclear Fission 19.8Nuclear Reactors 19.9Nuclear Fusion 19.10Effects of Radiation Predicted Indoor Radon Levels

Section 19.6 Nuclear Energy Return to TOC 29 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

Section 19.7 Nuclear Fission Return to TOC Copyright © Cengage Learning. All rights reserved 30 Releases 2.1  J/mol of uranium-235 Each fission produces 3 neutrons.

Section 19.7 Nuclear Fission Return to TOC 31 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

Section 19.7 Nuclear Fission Return to TOC 32 A Schematic Diagram of a Nuclear Power Plant

Section 19.7 Nuclear Fission Return to TOC 33 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.

Section 19.7 Nuclear Fission Return to TOC 34 Nuclear Power plants locations throughout the world.

Section 19.7 Nuclear Fission Return to TOC 35 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?

Section 19.7 Nuclear Fission Return to TOC The first chain reaction was demonstrated by the Italian physicist Enrico Fermi in Chicago in Enrico Fermi ( ) As he brought together the critical mass, the atomic pile began to heat up. By inserting control rods he was able to control the nuclear reaction.

Section 19.7 Nuclear Fission Return to TOC 37 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

Section 19.7 Nuclear Fission Return to TOC 38 Nuclear Bombs Trinity Bomb Test First nuclear bomb /trinity_nuclear_weapon_test/

Section 19.7 Nuclear Fission Return to TOC 39 Nuclear Bombs Hiroshima bomb- Little Boy Equivalent to kilotons of TNT 70,000 killed immediately and 70,000 died afterward. Half from blast, a third radiation and rest from radioactivity Hiroshima before the bomb. Hiroshima after the bomb.

Section 19.7 Nuclear Fission Return to TOC 40 Hiroshima after the blast. Imprint of sitting person from gamma ray incineration. The sky turned pink from gamma rays and about 15 seconds later the shock wave hit.

Section 19.7 Nuclear Fission Return to TOC 41 Nagasaki-Fatman bomb Equivalent to kilotons of TNT. About 20,000 killed immediately and another 20,000 died afterward. A military target that contained a weapons factory.

Section 19.7 Nuclear Fission Return to TOC 42 Process of combining 2 light nuclei Produces more energy per mole than fission Powers the stars and sun Nuclear Fusion

Section 19.7 Nuclear Fission Return to TOC Copyright © Cengage Learning. All rights reserved 43 Requires extremely high temperatures Currently not technically possible for us to use as an energy source Nuclear Fusion

Section 19.7 Nuclear Fission Return to TOC 44 Nuclear fusion produces tremendous quantities of energy and has the potential of becoming the ultimate source of energy on earth. Nuclear Fusion

Section 19.7 Nuclear Fission Return to TOC Copyright © Cengage Learning. All rights reserved 45 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

Section 19.7 Nuclear Fission Return to TOC Copyright © Cengage Learning. All rights reserved 46 Effects of Short–Term Exposures to Radiation

Section 19.7 Nuclear Fission Return to TOC Copyright © Cengage Learning. All rights reserved 47 Typical Radiation Exposures for a Person Living in the U.S.