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nuclearoutline09 - AP Chemistry Nuclear Chemistry Notes...

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AP Chemistry Nuclear Chemistry Notes Radioactivity: Serendipitous discovery by Antoine Becquerel in 1896 Working with fluorescent compounds Exposure of photographic film from Uranium Ore 1903 Nobel Prize Ernest Rutherford 1919 Transmutation of Nitrogen into Oxygen Bombarded Nitrogen with α particles Radioactive substances (those w/ unstable nuclei) spontaneously decay into other substances with the emission of particles and energy Many radioactive elements and their characteristics were discovered by the Curies (Marie, Pierre and Irene (daughter)) -Ex. Radium, Polonium and the positron -The element Curium and the radiation unit the "Curie'' are and their characteristics were named in their honor. -Marie died of leukemia probably as a result of her work -She is the only person to win Nobel prizes in both physics and chemistry Radioactive isotopes = Radioisotopes Types of Nuclear Reaction Particles Name Symbol(s) Mass Charge Special Alpha α , 4 2 He 4 +2 Helium nucleus Beta β , 0 1 e 0 -1 electron Neutron n, 1 0 n 1 0 Positron 0 1 + β , 0 1 + e 0 +1 Positive electrons In the decay process the nuclear mass (A) and/or nuclear charge (Z) changes. Use left hand superscripts and subscripts to represent atomic mass (A) and number (Z), respectively X A Z (i.e. Rn 122 86 ) Important Nuclear Related Elements: Bismuth (Z=83) is the last element with a nonradioactive isotope Uranium (Z=92) is the last naturally occurring element
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Nuclear Reaction Summary: In writing equations for nuclear reactions the total mass and nuclear charge MUST be conserved Radioactivity for isotopes of light elements (See the neutron to proton ratio chart in your book to determine which isotopes of an element are “stable”[i.e. the stability strip]) The stability of the nucleus is related to the neutron to proton ratio (n/p or N/Z) If the mass of an isotope is greater than the average mass of that element (listed on the periodic table) then stability is generally achieved through beta emission β 0 1 1 + + Y X A Z A Z Note that the number of neutrons decreases by one and the number of protons increases by one as a neutron is turned into a proton. Charge is conserved by the production of a negatively charged electron (beta particle. Conversely, isotopes that are lighter than average achieve stability through positron emission 0 1 1 + + Y X A Z A Z Note that a proton is turned into a neutron with charge being conserved through the production of the positive electron (positron) Atoms can also achieve this effect through the process of electron capture Y X A Z A Z 1 0 1 + Here, the capture of an electron allows the proton to turn into a neutron (increasing the N/Z (neutron to proton) ratio) For elements up to Z=20 the stable ratio is about 1:1 In general, for Z up to 83 Use relative atomic mass to determine stable n/p ratio Isotopes with even numbers of each nucleon (p and n) are more stable (60% vs. 1.5% for odd p and/or n) Isotopes with Z>83 generally decay through alpha decay
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