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Ch. 19 -- Nuclear Chemistry. Discovery of Radioactivity Radioactivity was first observed in ______by.

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Presentation on theme: "Ch. 19 -- Nuclear Chemistry. Discovery of Radioactivity Radioactivity was first observed in ______by."— Presentation transcript:

1 Ch. 19 -- Nuclear Chemistry

2 Discovery of Radioactivity http://www.radiation-scott.org/timeline/table.htm Radioactivity was first observed in ______by the French scientist Henri Becquerel. He discovered that Uranium salts would “fog up” a photographic plate. In 1898, Marie Curie and her husband Pierre coined the term radiation and radioactivity and went on to discover several new elements: ___________ and ________. She went on to win 2 Nobel Prizes: 1903 in Physics & 1911 in Chemistry, but she died of ________ caused by radiation exposure in 1934 at the age of 66. Her husband died in 1906 after getting hit by a horse and buggy. Marie Curie 1896 Polonium Radium cancer

3 Nuclear Reactions Nuclear reactions involve the _________ instead of the ___________ as in a regular chemical reaction. The instability of the nucleus of a radioactive element causes the # of protons and neutrons to change. Some of the ______ can be converted into a tremendous amount of energy shown by a very famous equation: E=mc 2 Energy = (mass) x (speed of light) 2 c= 3.0 x 10 8 m/s nucleus electrons mass

4 Nuclear binding energy (BE) is the energy required to break up a nucleus into its component protons and neutrons. BE + 19F 9 1p + 10 1n 9 10 Mass defect (∆m) = 9 x (p mass) + 10 x (n mass) – 19F mass E = mc2 ∆m (amu) = 9 x 1.007825 + 10 x 1.008665 – 18.9984 ∆m = 0.1587 amu = 2.636x10-28 kg BE = 2.636x10-28 kg x (3x108 m/sec)2 = 2.37 x 10-11J 23.2 When this atom forms, a tiny amount of matter is converted to energy Energy = mass(kg) x [speed of light ]2 Speed of light = c = 300,000,000 m/sec This may look small, but it means that when 19 g of flourine forms there is 14,000,000,000 kJ of energy released. That’s the same as burning 285,000 tons of coal!

5 2.0141 kg Nuclear Reactions 1.0078 kg3.0160 kg 3.0160 – (2.0141 + 1.0078) = 0.0059kg E=mc 2 E= 0.0059 x (3.0 x 10 8 ) 2 = 5.31 x 10 14 Joules

6 What makes a nucleus stable or unstable? It depends on the p + and n o ratio. Z= Atomic # = p + A = Mass # = n o + p + “Nucleons” are just the particles in the nucleus. ex) 2 He A Z Element symbol 4

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8 Chemical vs. Nuclear Reactions

9 Nuclear Reactions: Radiation Nuclear reactions release 3 main types of radiation: – (α) Alpha Particles … ________ nucleus (2 p + and 2 n 0 ) – (β) Beta Particles… high energy ___________ – (γ) Gamma Rays… high energy _________________ radiation helium electrons electromagnetic

10 How To Write Nuclear Particles --α Particles … helium nucleus (2 p + and 2 n 0 ) 2 He --β Particles… high energy electrons -1 e --γ Rays… high energy electromagnetic radiation 0 γ 0 γ -- Positrons…positive charged electrons 1 e -- Neutrons…neutrally charged particles in the nucleus that contributes to the mass of an atom 0 n 4 0 0 0 1

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12 Balancing Nuclear Reactions In chemical reactions the elements stay the same. In nuclear reactions, the elements ________ but the mass #’s and atomic #’s are ___________. Alpha Emission Beta Emission change conserved

13 Alpha Decay

14 Beta Decay

15 Another type of nuclear reaction is “electron capture” where an atom “_________” one of its own electrons. absorbs

16 Positrons: They are just like an electron, but they have a (___) charge instead of a negative charge. +

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18 Types of Decay--Summary

19 Nuclear Fission In fission, the nucleus _______ apart.(Fission is division.) Atom bombs and nuclear power plants use fission of U-235. splits

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21 Nuclear Fission: Chain Reaction

22 Detecting Radiation When the argon gas is hit by a particle, it ionizes and produces a current…“click”.

23 Nuclear Power Currently about _____ nuclear power plants in the U.S. and about _____worldwide. _____ of the world’s energy comes from nuclear. There are ___ nuclear power plants in Illinois. The closest one to us is in _________. 103 435 17% 6 Clinton

24 Clinton, IL Nuclear Power Plant

25 1000 MegaWatt Power Plant Pollution Coal-Fired vs. Nuclear

26 Nuclear Power Plants Nuclear power plants use the heat of a controlled nuclear fission reaction to ______ water that makes steam which turns a _________ and that produces electricity. boil turbine

27 Nuclear Power Plant “Disasters” One possible type of reactor disaster is known as a __________. In such an accident, the fission reaction goes out of control, leading to the emission of great amounts of radiation. meltdown

28 In ______, a much worse disaster struck Russia's Chernobyl nuclear power plant. In this incident, a large amount of radiation escaped from the reactor. Hundreds of thousands of people were exposed to the radiation. Several _______ died within a few days. In the years to come, thousands more may die of cancers induced by the radiation.Chernobyl nuclear power plant 1986 dozen

29 Chernobyl Sarcophagus

30 Nuclear Fusion In Fusion, nuclei combine to form a _________ nucleus. When the p + and n 0 bind, this releases tremendous amounts of ________. Nuclear fusion occurs in the _____ and other stars. heavier energy sun

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32 Spiderman 2—Tritium

33 Medicine imaging and tumor treatments Thyroid imaging using Tc-99 Uses of Nuclear Radiation

34 Food Irradiation Food can be irradiated with gamma rays from 60 Co or 137 Cs. Irradiated milk has a shelf life of __________without refrigeration. USDA has approved irradiation of _______ and eggs. 3 months meats

35 Isotope Half-Life Radiation Emitted Carbon-14 5,730 years  Radon-222 3.8 days  Uranium-235 7.0 x 108 years  Uranium-238 4.46 x 109 years  Radiocarbon Dating--The radioactivity of a sample can be used to determine how _____ it is. Half-life: The time for ______ of the nuclei to decay. old half

36 Half-Life Graph

37 Half life practice problems Astatine has a half-life of about 400 minutes. If you started with 1000 mg of At, how much would you have after 20 hours? x 1 hour 60 min = 1200 mins 1200 mins / 400 mins = 20 hours 3 Which means “cut in half” 3 times 1000 mg / 2 = 500 mg / 2 = 250 mg/ 2 = 125 mg


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