
<p> Nuclear Chemistry I: Definitions 1) Nuclear Chemistry: deals with the changes in the nucleus of the atom</p><p>2) Transmutation: the conversion of one element to another by means of a nuclear change.</p><p>3) Natural Radioactivity: the spontaneous breakdown of atomic nuclei, accompanied by the release of some form of radiation.</p><p>4) Induced radioactivity: artificial radioactivity produced by bombarding the nuclei of stable atoms with high energy particles, thereby producing radioactive atoms.</p><p>5) Radioisotopes: an isotope of an element that emits radiation. *All elements that have an atomic number than 83 have no stable isotopes! 6) Alpha particles: the nucleus of helium</p><p>7) Beta particles: an electron</p><p>8) Gamma rays: high frequency electromagnetic waves similar to x-rays, but of greater frequency</p><p>9) Positron: a positive subatomic particle with the same mass at the electron. Its charge is equal in quantity but opposite in sign to that of the electron.</p><p>10)Nuclear reaction: reaction involving a change in the nuclear contents of one or more atoms. In nuclear reactions, mass is converted to energy.</p><p>11)Nuclear fission: the splitting of an atomic nucleus into two smaller nuclei that are approximately equal in mass.</p><p>12)Fission reactors: a nuclear reactor used to control fission reactions. 13)Fusion reaction: a nuclear reaction in which two or more light nuclei combine to form a single nucleus.</p><p>14)Moderators: the substance used in a nuclear reactor to slow down the velocity of the neutrons.</p><p>15)Half-life: the time it takes for one half of the atoms in a given sample to decay.</p><p>16)Radioactive dating: the use of half-lives of radioisotopes in determining the age of the earth, ancient relics, and similar objects.</p><p>17) Tracer : Any radioisotope used to follow the path of a material in a system.</p><p>II: Natural Radioactivity: the spontaneous breakdown of atomic nuclei, accompanied by the release of some form of radiation A) Transmutation: the conversion of one element to another by means of a nuclear change </p><p>C) Types of Radioactive emissions (emanation) -All differ in mass, size and charge</p><p>4 1) Alpha Particle: 2 ___positive 2 charge______ ___helium nucleus______ ____ mass of 4amu </p><p>226 222 4 Example: 88Ra 86Rn + 2He</p><p>0 2) Beta Particle: -1 __negative charge______ __acts like a high speed electron __no mass______</p><p>235 235 0 Example: 92U 93Np + -1 3) Gamma Radiation (NOT a Particle) __no charge______ __acts like a high speed x-ray but with a lot more energy __no mass______</p><p>0 4) Positron Particle: +1 __positive 1 charge______ __acts like positive electrons __no mass______</p><p>Summary of Radioactive emanations: Particle Symbol Mass Charge Relative Penetrating Power 4 alpha 2 4amu +2 low 0 beta -1 0 -1 moderate gamma 0 0 high 0 positron +1 0 +1 moderate</p><p>Separation of Radioactive emissions by charge:</p><p> </p><p>Positively Charged Plate Negatively Charged Plate + - + - + - + - D) Half-life: the time it takes for half of the atoms in a given sample of an element to decay </p><p>*Some selected half-lives are found on Table N *All reactions on Table N are Natural Transmutation *Formulas for half-life reactions are found on Table T 1) Fraction Remaining = (1/2)n where n refers to the number of half-lives. 2) (n) = Number of Half-lives = total time half-life of isotope 3) Original Mass = Final Mass x 2n where n refers to the number of half-lives</p><p>Example: What fraction remains of an original sample of I-131 at the end of 32.28 days? Half-life of I-131 is 8.07 days. Therefore 4 half-lives have occurred. (1/2)n = (1/2)4 = 1/16</p><p>Example: What is the half-life of an element that decays from 100g to 25g in 30 days? 100g50g25g = 2 half-lives Therefore one half-life equals 15 days</p><p>Example: If we start with 36 g of 42K, how many grams will remain after 37.2 hours? 37.2 hours 12.4 hours = 3 half-lives 36g18g9g4.5g</p><p>Half-life problems 1. If you start with 75 g of P-32, how many grams will be left after 42.9 days?</p><p>42.9 days 14.3 days = 3 half-lives 75g37.5g18.75g9.375g</p><p>2. After 4800 years, there is 2.0 g of Ra-226 remaining. What was the original mass of the sample? Original Mass = Final Mass x 2n 4800 years 1600 years = 3 half-lives Original Mass = 2.0g x 23 = 16g </p><p>3. A 40 gram sample of P-33 decays to 10 grams in 50 days. What is the half-life of P- 33? 40g20g10g = 2 half-lives Therefore one half life equals 25 days</p><p>4. What fraction of C-14 remains of a 1 gram sample after 17,190 years? 17190 years 5730 years = 3 half-lives Fraction Remaining = (1/2)n = (1/2)3 = 1/8</p><p>III: Artificial Radioactivity A) Artificial Transmutation: artificial radioactivity produced by bombarding the nuclei of stable atoms with high energy particles, thereby producing radioactive atoms </p><p>B) Fission Reactions: the splitting of an atomic nucleus into two smaller nuclei by bombardment of a neutron (Nuclear Bomb). *Nuclear Reactors are fission reactors.</p><p>235 1 142 191 1 Example: 92U + 0n 56Ba + 36Kr + 3( 0n) + Energy</p><p>Fusion Reactions: a nuclear reaction in which ______. Requires huge amounts of pressure and extremely high temperatures. Produces much more energy than fission. Occurs naturally on the sun. (H-bomb)</p><p>2 2 4 Example: 1H + 1H 2He + Energy IV: Uses of Radioactive Isotopes:</p><p>A) Lab: to trace chemical reactions B) Industry: Radiating food to preserve by killing bacteria, mold, insect eggs </p><p>C) Medicine: must have relatively short half-lives and be quickly eliminated from </p><p> the body. </p><p>1) I-131 diagnosing and treating Thyroid conditions (half-life 8.07 days)</p><p>2) Co-60 emits large amounts of gamma radiation as it decays, these rays can </p><p> be aimed at cancerous tumors (half-life 5.26 years)</p><p>3) Ra-226 used in treatment of certain cancers (half-life 1600 years) </p><p>4) Tc-99 used in diagnosis of brain tumors (half-life 2.13x10 5 years </p><p>D) Geology: 1)Fossils C-14 to C-12 ratio (while alive they are in equal amounts, </p><p> once an organism dies C-14 is no longer taken in)</p><p>2) Rocks U-238 to Pb-206 ratio (U-238 decays through a series of steps </p><p> until it forms stable Pb-206. As time passes, the amount of U-238 decreases </p><p> while the amount of Pb-206 increases). </p><p>V: Balancing Nuclear Equations</p><p>Steps for Balancing:</p><p>1) Due to the Law of the Conservation of Matter, whatever is on the left side of the </p><p> equation must also be on the right side of the equation. </p><p>2) Add the mass numbers on the left side of the equation, this MUST equal the total </p><p> mass numbers of the right side of the equation.</p><p>3) Add the atomic numbers on the left side of the equation, this MUST equal the total </p><p> atomic numbers on the right side of the equation. 32 1 1 32 Example: 16S + 0n 1H + 15P</p>
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