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Wilhelm Rontgen • 1895 German Scientist Playing with a Crookes tube • Sitting in a dark lab, tube covered with black paper, held up a book to the tube . . . • Image of key appeared on paper painted with Barium across the room • The key had been a bookmark Rontgen’s Lab • • • • Rontgen thought he was hallucinating Told no one Shut himself in the dark lab for seven weeks Held up a metal plug and saw … his BONES “Black Magic” • Took a picture of wife’s hand (afraid, she never went back to the lab) • Showed that these images were real • Rontgen began to document and rationalize his work w/ physics knowledge of the time The Nobel Prize in Physics 1901 Wilhelm Conrad Röntgen Namesake Element: Rontegenium • Atomic # 111 • Atomic Weight 272 Discovered in 1994, Germany Highly Radioactive, but this element does not emit x-rays FUSION AND FISSION First, a little bit about energy Forms of Energy • The five main forms of energy are: – Heat – Chemical – Electromagnetic – Nuclear – Mechanical Heat Energy • The internal motion of the atoms is called heat energy, because moving particles produce heat. • Heat energy can be produced by friction. • Heat energy causes changes in temperature and phase of any form of matter. Chemical Energy • Making and Breaking bonds • Chemical Energy is required to bond atoms together. • And when bonds are broken, energy is released. Chemical Energy • Fuel and food are forms of stored chemical energy. Electromagnetic Energy • Power lines carry electromagnetic energy into your home in the form of electricity. Electromagnetic Energy • Light is a form of electromagnetic energy. • Each color of light (Roy G Bv) represents a different amount of electromagnetic energy. • Electromagnetic Energy is also carried by X-rays, radio waves, and laser light. Mechanical • Kinetic /Potential Nuclear Energy • The nucleus of an atom is the source of nuclear energy. • Energy holding nucleus together Nuclear Energy • Nuclear Energy is the most concentrated form of energy! • 2 major reactions :Fission & Fusion Fusion • Nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus. • The fusion of two nuclei lighter than iron or nickel generally releases energy. • The fusion of nuclei heavier than them absorbs energy. Result: gain or loss of energy Nuclear Fusion Nuclear Fusion Example The sun’s energy is produced from a nuclear fusion reaction in which hydrogen nuclei fuse to form helium nuclei. NUCLEAR FISSION • Fission may be defined as the process of splitting an atomic nucleus into fission fragments • The fission fragments are generally in the form of smaller atomic nuclei and neutrons • Large amounts of energy are produced by the fission process More about fission • Fissile nuclei are generally heavy atoms with large numbers of nucleons • The nuclei of such heavy atoms are struck by neutrons initiating the fission process • Fission occurs due to electrostatic repulsion created by large numbers of protons within the nuclei of heavy atoms Nuclear Fission Neutron induced in U235 Neutrons may: 1 - Cause another fission by colliding with a U235 nucleus • Creates two smaller nuclides and free neutrons • The free neutrons potentially collide with nearby U235 nuclei • May cause the nuclide to split as well Each split (fission) is accompanied by a large quantity of E-N-E-R-G-Y 2 - Be absorbed in other material 3 - Lost in the system If sufficient neutrons are present, we may achieve a chain reaction Fission Example Where does the energy come from? We often say that matter cannot be created nor destroyed. However . . . Einstein taught us that Energy and matter are different forms of the same thing! E= 2 mc Mass Defect • The nucleus – is composed of protons and neutrons – the actual mass is less than the mass of the separate particles. • The "missing" mass is in the form of energy holding the nucleus together. 5/6/2017 Uranium-238 The nuclear mass of uranium-238 is 238.0003 amu nucleons (protons & neutrons) 238U 92 atomic number (protons) 5/6/2017 A proton is 1.00728 amu A neutron is 1.00867 amu What mass is expected for the nucleus of 238U? Uranium-238 92 protons (92)(1.00728) = 92.6698 146 neutrons (146)(1.00867) = 147.2658 predicted mass = 239.9356 actual mass = 238.0003 mass defect = 1.9353 amu 5/6/2017 Masses of Atoms The nuclear mass of 238U is 238.0003 Why does the Handbook of Chemistry and Physics list the mass of uranium238 as 238.0508? (92)(0.0005488) + 238.0003 = 238.0508 5/6/2017 Binding Energy • The mass defect indicates the total energy involved in holding the nucleus together. • To determine the stability of the nucleus, the binding energy per nuclear particle is a better measure. 5/6/2017 Binding Energy of 238U actual mass 238.0003 predicted mass 239.9356 1.9353 amu DE = Dmc2 = 931.5 MeV/amu What is the binding energy per nucleon of 238U? Binding Energy of 238U Binding energy per nucleon (1.9353 amu)(931.5 MeV/amu) = 238 nucleons = 5/6/2017 7.57 MeV Binding Energy 62Ni 5/6/2017 The nuclei with the greatest binding energy per nucleon are the most stable. E= 2 mc • Matter can be changed into energy • In the equation above: – E = energy – m = mass – c = speed of light • Small amount of mass becomes a HUGE amount of energy Chemical Reactions • Involve changes in electrons – Acids & Bases, combustion, displacement • The same atoms appear on both sides of the reaction. • Follows Dalton’s Law of Conservation of Mass • Small amount of energy generated – Burning fossil fuels Nuclear Reactions • Involve changes in the nucleus – Nuclear fusion, nuclear fission • New atoms appear as products of the reaction. • Breaks Dalton’s Law of Conservation of Mass • Large amount of energy generated – 1 million times more than chemical reactions – Nuclear fusion on the sun – Nuclear fission for reactors Decay vs. Nuclear Reactions • Alpha, beta, and gamma • Nuclear reactions involve decay occur as ONE more than just getting rid of atom tries to increase a few protons or neutrons. it’s stability by getting rid The new atoms produced of a few neutrons, or are VERY different protons & neutrons. elements than the reactant. • The product is an alpha, • Nuclear reactions must be beta, or gamma particle started, so there are 2 and ONE new atom. things on the left hand side. There is only ONE thing – Nuclear fission: makes 2 on the left hand side. or more much smaller atoms – Nuclear fusion: makes 1 much larger atom Nuclear Fission Alpha Decay What are the differences between the 2 above nuclear equations?? Review • Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc2) • Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei • Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus Quiz • Which nuclear process produces large amounts of energy? A. Fission B. Fusion C. Both fission & fusion D. Neither fission nor fusion Quiz • Fission is the process that _________ atomic nuclei. A. Combines B. Burns up C. Stores D. Splits Quiz • Mass may be converted into energy. A. True B. False Quiz • The fission process requires heavy atomic nuclei. A. True B. False Quiz • Name a nuclear reaction that occurs within the sun: Bonus • Explain this equation: E = mc2