Chapter 25; Nuclear Chemistry

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who discovered radioactivity?
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Becquerel, Marie Curie, Pierre Curie
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radioisotope
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form of an atom that is unstable & loses particles from the nucleus
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alpha particle
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radiation composed of 2 protons and 2 neutrons
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beta particle
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composed of fast-moving electrons
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charge of a beta particle?
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-1
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charge of an alpha particle?
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+2
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gamma radiation
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high energy electromagnetic radiation given off as PART of a decay
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charge of gamma radiation?
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compare the subatomic particles involved in nuclear and chemical reactions
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protons, electrons, and neutrons can be invloved in cuclear change; only electrons are involved in chemical change
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how do you know whether the reaction is chemical or nuclear when an atom undergoes a reaction and attains a more-stable form.
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if the new, more stable form of the atom has an identitiy different from the original atom or gamma radiation has been released, a nuclear process has occurred
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compare and contrast chemical reactions and nuclear reactions in terms of energy changes and the particles involved.
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nuclear reactions release more energy per mole. nuclear reactions involve neutrons and protons, wehreas chemical reactions involve electrons
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what is the difference between x-rays and gamma rays?
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x-rays are produced by materials that are in an excited electron state. gamma rays are produced by radioactive sources.
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25-2
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transmutation
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the conversion of one atom to another type by changing the nucleus The atomic number is altered Whether an atom spontaneously decays and what type if radiation it emits depends on its neutron to proton ratio
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Nucleons
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Protons and neutrons are referred to as
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Neutron to proton ratio
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The stability of a nucleus can be correlated to its neutron to proton (n/p) ratio For atoms with low atomic numbers (<20), the most stable nuclei are those with 1:1 n/p As atomic numbers increase more and more neutrons are needed to produce a strong nuclear force that is sufficient to balance the electrostatic repulsion force between protons. The n/p will gradually increase to 1.5:1
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Beta decay
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Type of decay that decreases the number of neutrons in the nucleus
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Alpha decay
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All nuclei with more than 82 protons are radioactive and decay spontaneous. These very heavy nuclei often decay by emitting alpha particles
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For nuclei with low n/p what are two common radioactive decay processes?
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Positron emission and electron capture These 2 processes tend to increase the n/p ratio bringing the atom closer to the band if stability
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positron emission
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radioactive decay process that involves the emission of a positron from a nucleus. a positron is a particle with the same mass as an electron but opposite charge, thus, it is represented by the symbol e^+ or beta^+ during positron emission, a proton in the nucleus is converted into a neutron and a positron and then position is emitted
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electron capture
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ocurs when the nucleus of an atom draws in a surrounding electron, usually one ferom the loswet energy level. this captured eledtron combines with a proton to form a neutron the atomic number of the nuclues decreases by 1 as a resoult of electron capture
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describe what happens to an unstable nucleus
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unstable nuclei decay by emnitting alpha or beta radiation until they form a stable element
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radioactivity
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penetrating rays & particles given off by unstable nuclei
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half-life
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the amount of time for 1/2 the radioactive nucleus to decay
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describe the forces acting on the particles within a nucleus and explain why neutrons are the glue holding the nucleus together
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protons are positively charged and repel each other. neutrons do not repel easch other or protons. the sterong nuclear force is an attractive force that acts on both protons and neutrons in the nucleus. the greater the number of neutrons in the nucleus, the greater the ftrong nuclear force.
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25-3
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trans uranium elements
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elements with atomic numbers greater than 93 and have been produced in the laboratory by induced transmutaion and are radioactive
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einstein’s equation
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the equation relates mass and energy. it states that any reaction produces or consumes energy due to a loss or gain in mass. energy and mass are equivalent.
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mass defect
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the difference in mass between a nucleus and its component nucleons the mass of the nucleus is always less than the sum of the masses of the indivieual protons and neutrons that comprise it.
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nuclear FISSION
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the splitting of a nucleus into smaller, more stable fragments the fission of a nucleus is accompanied by a very large release of energy
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nuclear FUSION
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the process of binding smaller atomic nuclei into a single larger and more stable nucleus.
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in fission, what is the large nuclei split by?
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neutrons
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T/F Great amounts of energy can be liberated from small amounts of matter in nuclear reactions.
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True
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T/F The amount of U-235 in a nuclear reactor should always be kept subcritical
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False
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T/F Nuclear power plants do not contribute to pollution
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T-air pollution F-nuclear waste
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T/F Inserting boron or cadmium rids into the reactor core can control a fission reaction
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True
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Describe the process that occurs during a nuclear chain reaction and explain how to monitor a chain reaction in a nuclear teactir
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A neutron strikes a target nucleus such as u-235, which then splits into multiple fission fragments and releases several neutrons. These neutrons collide with other nuclei, causing additional fissions and sustaining the reaction. To control the chain reaction in a nuclear reactor, control rods if cadmium and boron are used to absorb some of the neutrons released during the reaction.
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How can nuclear fission be used to generate electric power?
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Fission reactions heat water and form steam. The steam spins turbines that produce electric power.
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Relate binding energy per nucleon to mass number.
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The binding energy per nucleon reaches a maximum value fir mass numbers around 69amu.
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Describe what is meant by subcritical mass and supercritical mass.
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The mass is subcritical if most of the neutrons escape the material instead of hitting other material. The mass is supercritical if most neutrons hit other material.
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How is it possible that both the splitting of nuclei (fission) and the combining of nuclei (fusion) release tremendous amounts of energy?
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With fission, A large nucleus splits into smaller nuclei.the binding energy of the large nucleus is greater than the sum of the binding energies of the smaller nuclei. That difference in energy is released. With fusion, two smaller nuclei combine to form a larger nuclei.the sum of the binding energies of the smaller nuclei is greater than the binding energy of the larger nucleus. Again the difference in energy is released.
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Describe the current limitations of fusion as a power source.
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A lot of energy is required to initiate the reaction. Currently no materials are capable of withstanding the very high temperature reached during reactions.
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25-4
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O > o o is an example of what process?
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fission
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o o > O is an example of what process
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fusion
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fusion or fission produces hazardous waste?
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fission
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what does fusion produce?
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helium
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above the atomic number 20, there are more _______ than protons
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neutrons
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critical mass
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the minimum mass of a sample of fissionable material necessary to sustain a nuclear chain reaction.
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0/-1 e is what decay?
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beta decay
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4/2 He is what decay?
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alpha decay
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atomic #s below 18 have a __:__ stability ratio
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1:1
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penetrating power of the 3 main types of radiation:
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A > | B > | > | C > | > | > |
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list three methods for detecting or measuring radiation
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1. Geiger counter 2. scintillation 3. film ID badge
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1/0 n -> 1/1 p + 0/-1 e + anti neutrino is what process?
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going from neutron -> proton (+ beta particle)
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how to get a proton from a neutron:
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beta decay
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proton to neutron process is called:
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positron emission
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1/1 p -> 0/-1 e + 1/0 n + neutrino is what process?
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positron emission
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the area of a nuclear stability graph plotted with stable nuclei is called…?
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the band of stability
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protons and neutrons are referred to as:
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nucleons
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induced transmutation is caused by what…?
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bombarding a nucleus with high-velocity particles
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what does induced transmutation do?
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changes it to a new element

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