1 Nuclear Chemistry Chapter 25

2 Nuclear Chemistry Uses

3 Radioactivity One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of ________ ( ).One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of ________ ( ). She discovered ________, the spontaneous disintegration of some elements into smaller pieces.She discovered ________, the spontaneous disintegration of some elements into smaller pieces. radioactivity Marie Curie

4 Band of Stability and Radioactive Decay Band of Stability and Radioactive Decay

5 Nuclear Reactions vs. Normal Chemical Changes Nuclear reactions involve the _________Nuclear reactions involve the _________ The nucleus opens, and the ______________________are rearrangedThe nucleus opens, and the ______________________are rearranged The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called _________________The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called _________________ “Normal” Chemical Reactions involve, ____________ not protons and neutrons“Normal” Chemical Reactions involve, ____________ not protons and neutronsnucleus protons and neutrons binding energy electrons

6 Mass Defect Some of the mass can be converted into energySome of the mass can be converted into energy Shown by a very famous equation!Shown by a very famous equation! E=mc 2 EnergyMass Speed of light

7 Types of Radiation ___________– a positively charged helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons___________– a positively charged helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons Beta (β) – _______________Beta (β) – _______________ ___________– pure energy; called a ray rather than a particle___________– pure energy; called a ray rather than a particle Gamma (γ) electron Alpha (ά)

8 Other Nuclear Particles ______________ ______________ ___________ – a positive electron ___________ – a positive electron Proton – usually referred to as hydrogen-1Proton – usually referred to as hydrogen-1 Any other elemental isotopeAny other elemental isotopeNeutron Positron

9 Geiger Counter Used to detect ____________________ Radioactive substances

10 Penetrating Ability

11 Balancing Nuclear Reactions In the ____________ (starting materials – on the left side of an equation) and _______ (final products – on the right side of an equation) Atomic numbers must balance and Mass numbers must balance Use a particle or isotope to fill in the missing protons and neutrons products reactants

12 Nuclear Reactions Alpha emissionAlpha emission Note that mass number (A) goes _________ and atomic number (Z) goes _____________ _____________ (nuclear particles… protons and neutrons) are rearranged but conserved Down by 2 Down by 4 Nucleons

13 Nuclear Reactions Beta emissionBeta emission Note that mass number (A) is ___________ and atomic number (Z) ______________ Goes up by 1 unchanged

14 Other Types of Nuclear Reactions Positron ( 0 +1  ): a positive electron Electron capture: Electron capture: the capture of an electron 207

15 Learning Check What radioactive isotope is produced in the following bombardment of boron? 10 B + 4 He ? + 1 n 5 2 0

16 Write Nuclear EquationsWrite Nuclear Equations! Write the nuclear equation for the beta emitter Co-60.

17 Uranium-238 Decay Series Uranium-238 Decay Series

18 Artificial Nuclear Reactions New elements or new isotopes of known elements are produced by bombarding an atom with a subatomic particle such as a proton or neutron -- or even a much heavier particle such as 4 He and 11 B. Reactions using _____________ are called  reactions because a  ray is usually emitted. _________________used in medicine are often made by  reactions. neutrons Radioisotopes

19 Artificial Nuclear Reactions (Transmutations) Example of a  reaction is production of radioactive 32 P for use in studies of P uptake in the body P n ---> 3215P + 

20 Transuranium Elements Elements beyond 92 (transuranium) made starting with an  reaction U n ---> ---> Np  Np ---> Np ---> U +  Pu  U

21 Nuclear Fission wVideo.php?video_id=173394http://www1.teachertube.com/members/vie wVideo.php?video_id= vdP_0http:// vdP_0

22 Nuclear Fission

23 Representation of a fission process.

24 Nuclear Fission & POWER Currently about 103 nuclear power plants in the U.S. and about 435 worldwide.Currently about 103 nuclear power plants in the U.S. and about 435 worldwide. 17% of the world’s energy comes from nuclear.17% of the world’s energy comes from nuclear.

25 Figure 19.6: Diagram of a nuclear power plant.

26 Nuclear Fusion

27 Nuclear Fusion Fusion __________________ 2 H + 3 H 4 He + 1 n Occurs in the ____________________ Energy small nuclei combine sun and other stars

28 Nuclear Fusion Fusion Excessive heat can not be contained Attempts at “cold” fusion have ______________ “Hot” fusion is difficult to contain Failed

29 Half-Life HALF-LIFE is the time that it takes for ______________________________HALF-LIFE is the time that it takes for ______________________________ The rate of a nuclear transformation depends only on the “reactant” concentration.The rate of a nuclear transformation depends only on the “reactant” concentration. 1/2 a sample to decompose

30 Half-Life Decay of 20.0 mg of 15 O. What remains after 3 half-lives? After 5 half-lives?

31 Kinetics of Radioactive Decay For each duration (half-life), one half of the substance decomposes. For example: Ra-234 has a half-life of 3.6 days If you start with 50 grams of Ra-234 After 3.6 days > __________ After 7.2 days >___________ After 10.8 days > _________ 25 grams 12.5 grams 6.25 grams

32 Learning Check! The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 39 hours?

33 Effects of Radiation

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35 Radiocarbon Dating Radioactive C-14 is formed in the upper atmosphere by nuclear reactions initiated by neutrons in cosmic radiation 14 N + 1 o n ---> 14 C + 1 H The C-14 is oxidized to CO 2, which circulates through the biosphere. When a plant dies, the C-14 is not replenished. But the C-14 continues to decay with t 1/2 = 5730 years. Activity of a sample can be used to date the sample.

36 Nuclear Medicine: Imaging Thyroid imaging using Tc-99m CT BONE SCAN CT BONE SCAN

37 Radioactive Tracing (Using oxygen-18)

38 Food Irradiation Food can be irradiated with ______ from 60 Co or 137 Cs.Food can be irradiated with ______ from 60 Co or 137 Cs. Irradiated milk has a shelf life of 3 mo. without refrigeration.Irradiated milk has a shelf life of 3 mo. without refrigeration. USDA has approved irradiation of meats and eggs.USDA has approved irradiation of meats and eggs.  rays