Week 14 Notes
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This 2 page Class Notes was uploaded by Cassidy Zirko on Monday May 2, 2016. The Class Notes belongs to Chem 143 at University of Montana taught by Dr. Cracolice in Spring 2016. Since its upload, it has received 11 views. For similar materials see General Chemistry 2 in Chemistry at University of Montana.
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Date Created: 05/02/16
Week 14, Prof. Cracolice, Chem 143 Chapter 74: What is Radioactivity and Why does it Occur? 4/29/16 74.1 What is Radioactivity? Radioactivity spontaneous emission of rays resulting from decay and the breaking up the atomic nucleus Nuclides the nuclei of atoms of radioactive elements Radionuclides not stable nucleus, constantly changing to either isotopes or nuclides of different elements Alpha particles, alpha rays attracted to the negatively charged plate, ray has positive charge, a little penetrating power, nuclei of helium atoms Alpha decay emission of an alpha particle Beta rays negatively charged, identified as electrons, zero mass and a negative charge, has more penetrating power, stopped by lead beta decay Gamma rays not particles, high energy electromagnetic rays Only stopped by think layers of lead, no electronic charge Positron same mass as an electron but it is positively charged Positron and electron are annihilated when combined produces gamma photons Electron capture= occurs when an arbitrary electron is captured by the nucleus, proton or neutrons, can be reactant or product How do Chemists use Symbols to Describe Nuclear Charge? o Transmutation change from one element to another remaining nuclide has different atomic number , different number of protons o Nuclear equation shows reactant nuclides/particles on left and nuclides or particles on night o Equation is balance with neutrons and protons o A nuclear equation is balanced if sums of mass number on the 2 sides of the equation are equal and if the sums of the atomic number are equal ; How are Nuclear Reactions Different from Chemical Reaction? o Chemical reactions chemical properties depend on electrons outside the nucleus, nuclear properties depend on isotopes of the element o Radioactivity is independent of state of chemical combustion of radioactive isotope, ordinary chemical reactions, atoms keep identified o Nuclear and ordinary chemical changes involve energy, but the amount of energy for a given amount of reactant in a nuclear change is huge 74.2 What Factors Influence the Stability of Nuclei? Isotopes with low atomic number are more likely to have the same number of neutrons as protons but the atomic radio of the number of neutrons and protons doesn’t always equal one Week 14, Prof. Cracolice, Chem 143 The ratio between neutrons and protons can be as high as 1.5 Because of the interaction between 2 faces in the universe Positive charge of proton characterize of electromagnetic force Strong nuclear force strong because attractive force is stronger than the electrical forces Most elements have a large number of isotopes but the number of stable isotopes is small when comparted to the number of radioactive isotopes Even numbered protons and neutrons have more common stable nuclei than odd All nuclei with 84 or more protons are radioactive and very unstable How do Radioactive Isotope Decay? o Mass number stays the same, atomic number increase by 1 o Neutron divide into proton and electron o Radioactive decay series the decay of radioactive elements 74.3 How do Scientists Change an Element into Another? Nuclear bombardment bombardment of the nucleus with alpha particles Induced or artificial radioactivity decay of radionuclide there isn’t found in nature Particle accelerator use electrical fields to increase the kinetic energy of charged particles that bombard the nucleus
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