slide 1 Do Now Write a balanced nuclear equation for the alpha decay that produces uranium-238.

slide 2 Do Now x = 8 x = 3 x = 0.667

slide 3 Announcement Test #4 - Wed, Dec 10 (tentative) Nuclear Chemistry –The concept of radioactivity –Chemical vs nuclear reactions –Major types of radioactivity –Factors that determine nuclear stability –Band of stability –Predicting nuclear decay pathways –Writing and balancing nuclear equations –Nuclear binding energy & mass defect –Fission and fusion –Half-life and kinetics of decay

slide 4 Nuclear Reactions SWBAT explain the concepts of nuclear fission and fusion, predict which will happen based upon nuclear binding energy, and write balanced equations for each. 2-day lesson Write this in your notes

slide 5 Review Nuclear reactions A reaction that involves a change to an atom's nucleus. Can produce enormous amounts of energy

slide 6 Nuclear fusion - two nuclei joining together into one Two Types of Nuclear Reactions Nuclear fission - a nucleus splitting into two or more parts Write this in your notes

slide 7 A nucleus will undergo whichever process makes it more stable So how do we know the relative stability of different nuclei? What determines if a nucleus will undergo fission or fusion?

slide 8 ΔE required component parts nucleus How do we measure stability of a nucleus? The amount of energy required is directly related to the stability of the nucleus

slide 9 Write this in your notes Nuclear Binding Energy Nuclear binding energy is the energy required to split the nucleus of an atom into its component parts (e.g protons and neutrons) Explaining nuclear binding energy requires a complex discussion of Einstein's theory of mass-energy equivalence. You will only be responsible for explaining the concept of mass defect and its use in deriving nuclear binding energy

slide 10 How do we measure this energy?  Separating a nucleus into its component parts is not easy to do.  It requires huge amounts of energy.  It is hard to measure.

slide 11 But how to measure this energy?  But there is another way  We can measure this energy indirectly by measuring the mass difference  And using E = mc 2

slide 12 component parts nucleus Measure the mass difference Mass difference? What mass difference? Shouldn't the mass of the nucleus should be the sum of the component parts?

slide 13 component parts nucleus Measure the mass difference u u Difference is u

slide 14 Mass-Energy Equivalence

slide 15 Life is different in the nucleus Strong nuclear force is the most powerful force in the universe Because of strong nuclear force, a HUGE amount of energy is required to split the nucleus into its component parts With amounts of energy this large, the mass- energy equivalence is detectable.

slide 16 But how to measure this energy?  When this huge amount of energy is added to the system, the mass goes up.  How much?

slide u u Measure the mass difference component parts nucleus Difference is u This much!!! The difference between these two is called the mass defect

slide 18 Write this in your notes Mass Defect Mass defect is the difference between the mass of a nucleus and the mass of its component parts By measuring the mass defect, the nuclear binding energy can be determined –An example of this calculation is shown on pg 878 in your book Nuclear binding energy provides an estimate of relative stability of different nuclei High nuclear binding energy - high stability Low nuclear binding energy - low stability

slide 19 Last Class

slide 20 Sketch this graph in your notes Iron is the most stable element, with the highest binding energy. This is why iron is such an abundant element

slide 21 Fission reactions Fission Process where a nuclei splits apart The daughters are more stable than the parents so energy is released

slide 22 Fission reactions Fusion Process where two nuclei join together The daughters are more stable than the parents so energy is released Fusion reactions Fusion Reactions

slide 23 A nucleus will undergo whichever process makes it more stable Nuclear binding energy measures the relative stability of different nuclei The optimum mass is around A=60 −Mass number >60, fission is favored −Mass number <60, fusion is favored Write this in your notes!!! What determines if a nucleus will undergo fission or fusion?

slide 24 Fission Reactions Nuclear fission - a nuclei splitting into two or more parts

slide 25 Do Now Write a balanced nuclear equation for the alpha decay that produces uranium-238.

slide 26 Previous Classes

slide 27 Transmutation & Fissionable Fission always involves transmutation Transmutation is the conversion of one atom of an element to an atom of another element Sometimes this occurs spontaneously –e.g. radioactive decay Sometimes this is forced to occur –e.g. caused by bombardment with particles –Called "induced transmutation" Fissionable - material capable of undergoing fission upon bombardment Write this in your notes

slide 28 When uranium-235 is bombarded with neutrons, it can breaks apart (fissions) according to the equation: Write this in your notes Fission products Fission of Uranium-235

slide 29 U-236

slide 30 When uranium-235 is bombarded with neutrons, it can breaks apart (fissions) according to the equation: Fission products Fission of Uranium-235

slide 31 Fission reactions Fission Converts U-235 into More Stable Nuclei Notice that the nuclei of Mo and Sn have greater binding energy and therefore are more stable than U

slide 32 Writing Balanced Nuclear Equations

slide 33 Balanced the Mass Numbers Mass Number = 236 Mass Number (2 x 1) = 236

slide 34 Balanced the Atomic Numbers Mass Number = 236 Mass Number (2 x 1) = 236 Atomic Number = 92 Atomic Number (2 x 0) = 92

slide 35 Independent Practice 1 The fission of uranium-235 by a neutron can produce many fission products. For the case where it produces krypton-91 (Kr) and barium-142 (Ba), write the nuclear equation and determine how many neutrons are produced.

slide 36 Independent Practice 1

slide 37 Independent Practice 2 The fission of uranium-235 by a neutron can produce many fission products. For the case where it produces yttrium-97 (Y), five neutrons and another fission product, write the nuclear equation and determine how what other fission product is made.

slide 38 Independent Practice 2

slide 39 Independent Practice 3 The fission of plutonium-240 (Pu) by a neutron can produce many fission products. For the case where it produces lanthanum-137 (La) and rubidium-94 (Rb), write the nuclear equation and determine how many neutrons are produced.

slide 40 Independent Practice 3

slide 41 SERIOUSLY?!? All this arguing over a simple isotope, uranium-235? What is all the arguing about??? Benjamin NetanyahuMahmoud Ahmadinejad

slide 42 What makes U-235 so special? U-235 is a naturally-occurring isotope Typical uranium ore contains: >99% U-238 & <1% U-235 Uranium ore can become "enriched" in U-235 through a complex and difficult process 5-20% enriched uranium is needed for nuclear power >85% enriched uranium is needed for nuclear weapons

slide 43 U-235 is a naturally-occurring isotope capable of starting and propagating a nuclear chain reaction. Key Points Write this in your notes

slide 44 What is a Nuclear Chain Reaction? A nuclear chain reaction is a self-sustaining sequence of nuclear fission reactions. One atom undergoes fission This triggers another atom to undergo fission Which triggers another atom to undergo fission... The sequence, once started, continues with no external triggers

slide 45 U-235 is a naturally-occurring isotope capable of starting and propagating a nuclear chain reaction. A nuclear chain reaction is a self-sustaining sequence of nuclear fission reactions. Key Points Write this in your notes

slide 46 Fission products 1 neutron, 1 fission How does U-235 start & propagate a nuclear chain reaction?

slide 47 1 neutron, 1 fission Can these 2 neutrons cause 2 other fissions?

slide 48 Can these 2 neutrons cause 2 other fissions? Yes! 1 neutron, 1 fission

slide 49 2 neutrons, 2 fissions Fission products 1 neutron, 1 fission

slide 50 2 neutrons, 2 fissions 1 neutron, 1 fission Each neutron then causes one more fission reaction 4 neutrons, 4 fissions

slide 51 2 neutrons, 2 fissions 1 neutron, 1 fission Each neutron then causes one more fission reaction 4 neutrons, 4 fissions How does U-235 start & propagate a nuclear chain reaction? Because its fission creates more neutrons than it consumes!

slide 52 Fissile Material for Chain Reactions A material capable of sustaining a nuclear fission chain reaction with neutrons of any energy Fissile rule  90 ≤ Z ≤ 100  2Z - N = 43 ± 2 Different from a fissionable materials. All fissile materials are fissionable materials but not the other way around. Materials that require high energy neutrons are not considered fissile

slide 53 U-235 is a naturally-occurring isotope capable of starting and propagating a nuclear chain reaction. A nuclear chain reaction is a self-sustaining sequence of nuclear fission reactions. U-235 can do this because its fission creates more neutrons than it consumes. Key Points Write this in your notes

slide 54 Critical Mass Critical mass is another key factor to consider For a chain reaction to occur, there has to be enough fissionable atoms around to collide with released neutrons and propagate the chain. Not enough - subcritical mass Just enough - critical mass More than enough - supercritical mass Critical mass is the minimum amount of fissionable material necessary to sustain a nuclear chain reaction

slide 55

slide 56 U-235 is a naturally-occurring isotope capable of starting and propagating a nuclear chain reaction. A nuclear chain reaction is a self-sustaining sequence of nuclear fission reactions. U-235 can do this because its fission creates more neutrons than it consumes. Enough U-235 is needed to achieve critical mass, the minimum amount of fissionable material necessary to sustain a nuclear chain reaction Key Points Write this in your notes

slide 57 So where do we stand? Hassan RouhaniAli Hosseini Khamenei

slide 58 Fusion Reactions Nuclear fusion - two nuclei joining together into one

slide 59 Fission reactions Fusion reactions Fusion Process where two nuclei join together The daughters are more stable than the parents so energy is released The products are more stable than the starting material so: the reaction proceeds forward energy is released Fusion reactions

slide 60 Fusion Fusion is less familiar to most people Fusion is more difficult to initiate and sustain than fission The stars use fusion to generate energy

slide 61 Fusion Energy is Very Attractive Fuels are cheap and abundant –Reaction can hydrogen gas or other abundant elements Little radioactive waste Reactors can't get out of control –Fusion would just stop Large projects are trying to achieve fusion –Seeking to produce more energy than required to start the reaction

slide 62 Fusion of Carbon & Hydrogen

slide 63 Balance the Mass Number Mass Number = 13 Mass Number = 13

slide 64 Balance the Atomic Number Mass Number = 13 Mass Number = 13 Atomic Number = 7 Atomic Number = 7

slide 65 Equation is Balanced Mass Number = 13 Mass Number = 13 Atomic Number = 7 Atomic Number = 7

slide 66 Solve This Problem Two helium-3 atoms fuse together to form one helium-4 atom and some hydrogen-1. Write a balanced equations and determine how many atoms of hydrogen-1 are produced.

slide 67 Write the Reactants Two helium-3 atoms fuse together to form one helium-4 atom and some hydrogen-1. Write a balanced equations and determine how many atoms of hydrogen-1 are produced.

slide 68 Write the Equation Two helium-3 atoms fuse together to form one helium-4 atom and some hydrogen-1. Write a balanced equations and determine how many atoms of hydrogen-1 are produced.

slide 69 Balance the Mass Number Mass Number (2 x 3) = 6 Mass Number 4 + (2 x 1) = 6 Two helium-3 atoms fuse together to form one helium-4 atom and some hydrogen-1. Write a balanced equations and determine how many atoms of hydrogen-1 are produced.

slide 70 Balance the Atomic Number Mass Number (2 x 3) = 6 Mass Number 4 + (2 x 1) = 6 Atomic Number (2 x 2) = 4 Atomic Number 2 + (2 x 1) = 4 Two helium-3 atoms fuse together to form one helium-4 atom and some hydrogen-1. Write a balanced equations and determine how many atoms of hydrogen-1 are produced.

slide 71 Balanced Equation Two atoms of hydrogen-1 are produced. Two helium-3 atoms fuse together to form one helium-4 atom and some hydrogen-1. Write a balanced equations and determine how many atoms of hydrogen-1 are produced.

slide 72 Independent Practice 4

slide 73 Independent Practice 5

slide 74 Independent Practice 6

slide 75 Worksheet Start in class Finish for homework Be sure to ask for help if you need it

slide 76 Good video on mass defect

slide 77 Decay versus Fission By definition, most decay qualifies as a form of fission In common usage, however, the meanings are different Radioactive decay is a spontaneous process where the nucleus tries to get into the band of stability. The fragment lost is usually no bigger than  -particles In common usage, fission is an induced transmutation. It leads to the transient production of an unstable nucleus which undergoes fission. The fragments are usually larger than  -particles