Flashcard Answers on Nuclear Chemistry
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Henri Becquerel
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Discovery of radioactivity
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Marie Curie
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Radioactivity and discovery of Po and Ra
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Enrico Fermi
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First controlled nuclear chain reaction
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Irene Curie
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Created first artificial isotope 30P
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Williard Libby
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Carbon-14 Dating
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Lisa Meitner
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Nuclear fission
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Ernest Rutherford
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First nuclear transmutation
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August 13, 1942
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The establishment of the Manhattan Engineer district to develop and build the atomic bomb.
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July 16, 1945
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First bomb tested successfully from the Manhattan project.
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August 9, 1945
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Atomic dropped on Nagasaki
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April 26, 1986
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Chernobyl nuclear accident
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December 2, 1942
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Fermi first nuclear fission reaction
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August 6, 1945
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Atomic bomb dropped in Hiroshima
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October 31, 1952
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First H-bomb Enewetak Atoll in Pacific Ocean
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March 11, 2011
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Fukushima nuclear disaster after earthquake and tsunami.
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Nuclear reaction
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The reaction in which composition of nucleus is altered through the release of energy and mass
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List 5 characteristic of nuclear reactions that differ from chemical reactions
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1) One element to another element 2) protons and neutrons are involved in reaction 3) reactions involved in huge change in energy 4) Measurable changes in mass 5) Not affected by temperature or catalyst.
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What are Isotopes?
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Atoms of the same element but different mass (neutrons).
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What is the mass number and how does it differ from atomic mass?
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The atomic mass is the weighted average of all isotopes of an element. Mass # equal to protons + neutron
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What does the proximity of the mass number of an isotope to that element's atomic mass have to do with nuclear stability?
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If there is too many neutrons or protons in the nucleus, it will upset this balance disrupting the binding energy from the strong nuclear forces making the nucleus unstable.
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How do the chemical and physical properties of radioactive isotopes of an element compare to those of the stables one?
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Other than mass differences, the chemistry and most physical properties are the same
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What is different about the three isotopes of hydrogen that also identifies the difference between all of the isotopes of any one element?
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Different number of neutrons (same number of protons)
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Nucleons
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Protons and neutrons
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What is the difference between a nucleon and a nuclide?
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Nucleons makes up the nucleus and nuclide is a specie with specified numbers of protons and neutrons.
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Radioactive
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Its the spontaneous emission of matter or energy by isotope to reach more stable lower energy
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What is the physical state of radon and why is it dangerous?
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Radon is a gas and a carcinogen in lungs. Gas collects in basements
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List the 5 names of radioactivity decay
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1) Alpha emission 2) Beta Emission 3) Gamma Emission 4) Positron Emission 5) Electron capture
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What changes occurs in the nucleus when alpha decay happens
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Losses 2 protons and two neutrons. Atomic number decreases 2 units, mass number decreases 4 units.
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What changes occurs in the nucleus when beta decay happens
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A neutron is converted into a proton. Atomic number increases 1 unit
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What changes occurs in the nucleus when positron decay happens
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Proton is converted into neutron. Atomic number decreases 1 unit
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What changes occurs in the nucleus when gamma decay happens
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No change, only energy change
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What changes occurs in the nucleus when electron capture happens
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Proton is converted into neutron with the capture of an electron in the lowest level of energy. Atomic number decreases by 1 unit
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What is positron?
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Antiparticle of electron. All other properties of a positron are same as the electron.
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Write an equation that illustrates what usually happens to the positron that is emitted by the nucleus
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0/1 B- + 0/1 B+ = 2 gamma rays
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What does a nuclide that undergoes electron capture emit?
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X-rays. Loss of 1s electrons causes other orbitals to fill the hole.. Highest possible deltaE id the 2s to 1s, that mean that deltaE is in the x-ray region.
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What are gamma rays?
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High energy photons
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Write a nuclear equation that illustrates gamma emission?
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Neutron or proton move to lower nuclear energy level with release of deltaE: 60Co ->60Co + gamma rays
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What is the relative magnitude of the energy of gamma rays and why are they used for cancer treatment?
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Gamma rays have the largest of energy of the entire electromagnetic spectrum and therefore is used to kill cancer cells.
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What is a radioactive decay or disintegration series?
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Succession of steps a parent unstable nucleus undergoes to lower its energy
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What does the term parent, daughter, etc refer to?
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Terminology to indicated the succesive decay steps.
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What is significant about the band of stability?
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Band that contains all the stable nuclides and radioactive nuclides on plot of number of neutrons vs. number of protons
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If all ~250 stable isotopes are within this Band, where are the much greater number of nuclides that are radioactive on the figure? Why?
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If outside the band in any direction will be so unstable the atom will fall apart (disintegrated).
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What are the four major factors that determine nuclear stability of nuclides?
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1) n/p ratio 2) Odd/even number of nucleons 3) magic numbers 4)size greater than 83 are unstable
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Why is the significance of the fact that the general slope is greater than 1/1
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n/p ratio required for atoms to exist.
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What is the strong force?
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An attractive force in the nucleus that overcomes electrostatic repulsion
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When unstable nuclides decay, they usually select a mode that shifts them towards the band of stability. Why?
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If decay mode results in outside of band the nuclide will disintegrate
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What two unique attributes characterize all elements with atomic numbers more than 92?
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Synthetic and all isotopes are radioactive
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high neutron/proton ratio
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0/1 B- decay
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A low neutron/ proton ration
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B+ emission or electron capture
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Nuclides with Z>83
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alpha decay
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What is a radioisotope?
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An unstable nucleus that will spontaneously decay via emission to lower energy
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What is the half life of a radioisotope?
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Time required for 50% of nuclide to decay
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What kinetic order do all types o radioactive decay exhibit?
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First order kinectics
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Formula to find K
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K = (ln2)/(t1/2)
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Formula to find ratio
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ln(Nt/N0)=-kt
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Why are radioisotopes with short half lives used for diagnosis in nuclear medicine?
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Because it will decay faster
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What is nuclear binding energy?
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Energy required to break nucleus of atom into is component parts
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Why is there a mass difference between total mass of an isotope and the combined masses of its nucleons?
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Some mass is converted into the energy necessary to bind nucleons into a nuclide
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Equation that relates mass to energy
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Delta E= (delta m)(c)^2
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What is the source of the tremendous energy produced by nuclear reactions?
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Conversion of mass into energy
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How are mass defect and nuclear binding energy related
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They are the same and related by Delta E= (delta m)(c)^2
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What is the binding energy per nucleon and why is that parameter used rather than per nuclide when comparing nuclear stability?
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Total binding energy divided by total number of nucleons. Relative stability of nuclides distorted and don't factor out size.
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In terms of binding energy, what element is the energetically-favorable dividing the line between fission and fusion processes
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56/26 Fe most stable
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Nuclear Transmutation
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Non spontaneous conversion of one nucleus into another by bombardment with very high energy particles.
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What are the two main types of nuclear transmutation reactions?
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Fusion and Fission
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First Transmutation
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14/7 N + 4/2 He -----> 17/8 O + 1/1 H
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What are particles accelerators?
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Instruments that use magnetic fields and electricity to accelerate particles to very high KE for use as initiators in nuclear transmutation
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Name four types of nuclear accelerators
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Synchrotron, cyclotron, tevatron, large hadron collider
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What does the term naturally occurring isotope mean?
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Found in nature, not artificial
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Nuclear fusion
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Light nuclei combine to form heavier nuclei, with release of huge amounts of energy. (very non-spontaneous process)
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What is Tokamak?
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Containment device for plasma created by nuclear fusion using magnetic fields.
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Where does nuclear fussion occur every minute of every day and write a nuclear reaction that illustrates this process
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On the sun and other stars. 2/1 H + 3/1 H = 4/2 He + 1/0 n + 1.7 x 10^9 KJ/mol
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What is nuclear fission?
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The process in which a large nucleus splits into two intermediate-size nuclei, with the emission of neutrons and the conversion of mass into energy.
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In what main way is fission different from radioactive decay?
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Its non-spontaneous
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List an example of nuclear fission reaction
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235/92 U + 1/0 n -----> 92/36 Kr + 141/56 Ba + 3 1/0 n + energy
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Are all the fission events in a chain reaction identical?
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No, many different types of split nuclei created, different of n's created, and delta E's are also different
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What is a critical mass?
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Minimum mass of fissionable material necessary to sustain a chain reaction
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What is a chain reaction?
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Self sustaining series of reactions
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What is the minimum number of neutrons from each fission event that must be absorbed by other nuclei for a chain reaction to be sustained?
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2 or more neutrons products necessary
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What are control rods and what two elements are used to make rods in nuclear reactors?
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Neutron absorbing rods placed into the reactor with uranium rods. Made from boron-10 and cadmium-113
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What is a breeder reactor?
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Nuclear reactor that produces as well as consumes fissionable material
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What is a reactor core?
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Central part of the reactor core
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What is an isotope tracer?
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Radioactive substance used to follow a chemical process or complex sequence of biological reactions.
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What type of nuclear reaction was taking place to generate the electricity produced by the Onofre power plant near San Clemente?
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Nuclear fission
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Geiger counter
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A device that measures the amount of radiation by producing an electric current when it detects a charged particle (Ar ions)
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List four applications for ionization radiation
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Material flow, rxn pathways, medical diagnosis, activation analysis
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Scintillation Counter
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a device that uses a phosphor-coated surface to detect radiation
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What is radiocarbon dating?
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Method for determining age in once living object by measuring 14 C/12 C ratio
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Write the two nuclear equations that are the basis for the radio-dating process that is based on carbon-14
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14/7 N + 1/0 n ---> 14/6 C + 1/1 H (carbon 14) 14/6 C ---> 0/-1 B- + 14/7 N ( beta decay of carbon 14)
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What typed of materials can be radio-dated using carbon-14
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Method for determining age in once living object by measuring 14 C/12 C ratio
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Briefly explain how the carbon-14 dating method works.
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When alive carbon-14/carbon-12 ratio constant. When dead the carbon-14 decay (B-). Analysis of subsequent carbon-14/ carbon-12 ratio determine age of sample.
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Radioisotope dating depends on constant rate of decay and formation of various nuclides in a sample. How is the proportion of carbon-14 kept relatively constant in organism.
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Living system interact with their environment and there by maintain a carbon-14/ carbon-12 ratio.
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How old does a sample have to be before the carbon dating methods become unreliable?
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older than 36,000 years
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Radiation danger depends on what three factors?
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1) Type of radiation 2) half life 3) how biological system interact
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What is the relative external penetrating power of alpha, beta, and gamma "rays"?
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gamma (333) > beta (67) > alpha (1)
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What is the danger f alpha, beta, and gammas in terms of their relative internal (biological) damage?
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alpha > gamma >> beta
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Why is radioactive radiation called "ionizing radiation"?
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The radiation causes loss of electrons which creates ions. Very dangerous free radicals.
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What are "free radicals" and why are they dangerous?
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Chemicals species with unpaired electron making them very reactive and dangerous.
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What is the relative external penetrating power of alpha, beta, and gamma rays?
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gamma greater than beta greater than alpha
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What level of enrichment must be reached to be able to use the material in a fission atomic bomb?
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over 90%
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What is uranium enrichment?
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Take U-235 and make it percentage higher by centrifuging U-238
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When selecting radionuclides for medical application, what two properties are important in their selection?
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B - emission short half life
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List three forms of cellular damage that are caused by nuclear radiation
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1) Genetic damage 2) Reduced enzyme function 3) Destruction of protective fatty tissue
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What are free radicals and why are they dangerous?
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Chemical species with unpaired electrons
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Other than radioactivity, how do chemical and physical properties of radioactive isotopes of an element compare to those of the stable ones?
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Chemically they are the same, mass is slightly different. (neutrons)
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uranium enrichment
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Process to increase percentage of 235 U to create material for nuclear power plant and/or atomic bombs
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Power plants needs?
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3-4% 235 U
