Chapter 10 Chapter 10: Nuclear Physics Nuclear ?· Chapter 10 Nuclear Physics Chapter 10: Nuclear Physics Homework: All questions on the “Multiple- ... Fundamental Forces of Nature - Review

Download Chapter 10 Chapter 10: Nuclear Physics Nuclear  ?· Chapter 10 Nuclear Physics Chapter 10: Nuclear Physics Homework: All questions on the “Multiple- ... Fundamental Forces of Nature - Review

Post on 03-Feb-2018

214 views

Category:

Documents

2 download

Embed Size (px)

TRANSCRIPT

<ul><li><p>1</p><p>Chapter 10</p><p>Nuclear PhysicsChapter 10: Nuclear Physics</p><p>Homework: All questions on the Multiple-Choice and the odd-numbered questions onExercises sections at the end of the chapter.</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 2</p><p>Nuclear Physics</p><p> The characteristics of the atomic nucleus areimportant to our modern society.</p><p> Diagnosis and treatment of cancer and otherdiseases</p><p> Geological and archeological dating</p><p> Chemical analysis</p><p> Nuclear energy and nuclear diposal</p><p> Formation of new elements</p><p> Radiation of solar energy</p><p> Household smoke detector</p><p>Intro</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 3</p><p>Early Thoughts about Elements</p><p> The Greek philosophers (600 200B.C.) were the first people to speculateabout the basic substances of matter.</p><p> Aristotle speculated that all matter onearth is composed of only fourelements: earth, air, fire, and water.</p><p> He was wrong on all counts!</p><p>Section 10.1 Copyright Houghton Mifflin Company. All rights reserved. 10 | 4</p><p>Symbols of the Elements</p><p> Swedishchemist, JonsJakob Berzelius(early 1800s)used one or twoletters of theLatin name todesignate eachelement.</p><p>Section 10.1</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 5</p><p>Symbols of the Elements</p><p> Since Berzelius time most elementshave been symbolized by the first oneor two letters of the English name.</p><p> YOU are expected to know the namesand symbols of the 45 elements listedon Table 10.2.</p><p>Section 10.1 Copyright Houghton Mifflin Company. All rights reserved. 10 | 6</p><p>Names and Symbols of Common Elements</p><p>Section 10.1</p></li><li><p>2</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 7</p><p>The Atom</p><p> All matter is composed of atoms.</p><p> An atom is composed of three subatomicparticles: electrons (-), protons (+), andneutrons (0)</p><p> The nucleus of the atom contains the protonsand the neutrons (also called nucleons.)</p><p> The electrons surround (orbit) the nucleus.</p><p> Electrons and protons have equal butopposite charges.</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 8</p><p>Major Constituents of an Atom</p><p>Section 10.2</p><p>U=unified atomic mass units</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 9</p><p>The Atomic Nucleus</p><p> Protons and neutrons have nearly thesame mass and are 2000 times moremassive than an electron.</p><p> Discovery Electron (J.J. Thomson in1897), Proton (Ernest Rutherford in1918), and Neutron (James Chadwick in1932)</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 10</p><p>Rutherford's Alpha-Scattering Experiment</p><p> J.J. Thomsons plum pudding model predicted thealpha particles would pass through the evenlydistributed positive charges in the gold atoms.</p><p>a particle = helium nucleus</p><p>Section 10.2</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 11</p><p>Rutherford's Alpha-Scattering Experiment</p><p> Only 1 out of 20,000 alpha particlesbounced back.</p><p> Rutherford could only explain this byassuming that each gold atom had itspositive charge concentrated in a verysmall nucleus.</p><p> Diameter of nucleus = about 10-14 m</p><p> Electron orbit diameter = about 10-10 m</p><p> Atomic Mass is concentrated in thenucleus (&gt;99.97%)</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 12</p><p>Atomic Mass is Concentrated in theNucleus!</p><p> Therefore the volume (or size) of anatom is determined by the orbitingelectrons. The diameter of an atom is approximately</p><p>10,000 times the diameter of the nucleus.</p><p> If only nuclear material (protons andneutrons) could be closely packed into asphere the size of a ping-pong ball itwould have the incredible mass of 2.5billion metric tons!</p><p>Section 10.2</p></li><li><p>3</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 13</p><p>VisualRepresentation ofa Nucleus</p><p> Tightly PackedProtons andNeutrons</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 14</p><p>Atomic Designations</p><p> Atomic Number (Z) the # of protons in thenucleus (defines the element the # ofprotons is always the same for a givenelement)</p><p> Atomic Number also designates the numberof electrons in an element.</p><p> If an element either gains or loses electrons,the resulting particle is called and ion.</p><p> For example, if a sodium atom (Na) loses anelectron it becomes a sodium ion (Na+.)</p><p>Section 10.2</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 15</p><p>More Atomic Designations</p><p> Mass Number (A) protons + neutrons, orthe total number of nucleons</p><p> Isotope when the number of neutrons varyin the nucleus of a given element (alwayssame number of protons)</p><p> Only 112 elements are known, but the totalnumber of isotopes is about 2000.</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 16Section 10.2</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 17</p><p>Isotopes</p><p> Some elements have several isotopes(like carbon 12C, 13C, 14C)</p><p> Isotopes of a single element have thesame chemical properties (due to samenumber of electrons), but they havedifferent masses (due to varying numberof neutrons.)</p><p> Due to their various masses isotopesbehave slightly different during reactions.</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 18</p><p>Carbon Isotopes - Example</p><p>SymbolProtons</p><p>(Z)Neutrons</p><p>(N)Mass #</p><p>(A)</p><p>12C 6 6 12</p><p>13C 6 7 13</p><p>14C 6 8 14</p><p>Section 10.2</p></li><li><p>4</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 19</p><p>Three Isotopes of Hydrogen</p><p>In naturally occurring Hydrogen - 1 atom in 6000 isdeuterium and 1 in 10,000,000 is tritium. Heavy water = D2O</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 20</p><p>CommonIsotopes ofsome of theLighterElements</p><p>Section 10.2</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 21</p><p>Determining the Composition of an Atom</p><p> Atomic Number (Z) = 9</p><p> \ protons = 9 &amp; electrons = 9</p><p> Mass Number (A) = 19</p><p> A = N + Z {N = Neutron Number}</p><p> \ N = A Z = 19 9 = 10</p><p> neutrons = 10</p><p>Section 10.2</p><p>9</p><p> Determine the number of protons, electrons,and neutrons in the fluorine atom 19F</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 22</p><p>Atomic Review</p><p> Protons &amp; Neutrons in nucleus</p><p> Electrons orbit around nucleus</p><p> Mass Number (A) = protons + neutrons</p><p> Atomic Number (Z) = # of protons</p><p> Neutron Number (N) = # of neutrons</p><p> Isotope an element with different # ofneutrons (same # of protons)</p><p>Section 10.2</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 23</p><p>Atomic Mass</p><p> The weighted average mass of an atom ofthe element in a naturally occurring sample</p><p> The Atomic Mass is measured in unifiedunifiedatomic mass units (u)atomic mass units (u) basically the weightof a proton or neutron.</p><p> The 12C atom is used as the standard, and isassigned the Atomic Mass of exactlyexactly 12 u.</p><p> The weighted average mass of all carbon isslightly higher than 12 (12.011) becausesome is 13C and 14C.</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 24</p><p>Schematic Drawing of a Mass Spectrometer</p><p>Copyright Houghton Mifflin Company</p><p>The ion with the greatest mass is deflected the least, the ionwith the least mass is deflected the most.</p><p>Section 10.2</p></li><li><p>5</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 25</p><p>A Mass SpectrogramShowing the Three Isotopes of Neon and their relative</p><p>abundances</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 26</p><p>Calculating an Elements Atomic Mass</p><p> Naturally occurring chlorine is a mixtureconsisting of 75.77% 35Cl (atomic mass =34.97 u) and 24.23% 37Cl (atomic mass =36.97 u). Calculate the atomic mass for theelement chlorine.</p><p> Calculate the contribution of each Cl isotope.</p><p> 0.7577 x 34.97 u = 26.50 u (35Cl)</p><p> 0.2423 x 36.97 u = 8.96 u (37Cl)</p><p> Total = 35.46 u = Atomic Mass for Cl</p><p>Section 10.2</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 27</p><p>Fundamental Forces of Nature - Review</p><p> We have previously discussed twofundamental forces of nature gravitationaland electromagnetic.</p><p> The electromagnetic force between a proton(+) and an electron (-) is 1039 greater thanthe gravitational forces between the twoparticles.</p><p> Therefore the electromagnetic forces arethe only important forces on electrons andare responsible for the structure of atoms,molecules and all matter in general.</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 28</p><p>The (Strong) Nuclear Force</p><p> Remember that the nucleus of any atom isextremely small and packed with acombination of neutrons and protons (+.)</p><p> According to Coulombs Law like chargesrepel each other. Therefore the repulsiveforces in a nucleus are huge and the nucleusshould fly apart.</p><p> There must exist a third fundamental forcethat somehow holds the nucleus together.</p><p> For a large nucleus the forces arecomplicated.</p><p>Section 10.2</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 29</p><p>Large Nucleus &amp; the Nuclear Force</p><p> An individual proton is only attracted by the 6 or 7 closestnucleons, but is repelled by all the other protons.</p><p> When the # of protons exceeds 83, the electrical repulsionovercomes the nuclear force, and the nucleus is unstable.</p><p> Spontaneousdisintegration ordecay occurs toadjust for the neutron-proton imbalance.</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 30</p><p>Standard Model</p><p> Physicists have also identified a weaknuclear force within an atom.</p><p> This is a short-range force that revealsitself principally in beta decay.</p><p> Physicists have organized three of theknown atomic forces (electromagnetic,weak nuclear, and strong nuclear) into asingle unifying theory called thestandard model.</p><p>Section 10.2</p></li><li><p>6</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 31</p><p>Atomic Review</p><p> Mass Number (A) protons + neutrons,or the total number of nucleons</p><p> Isotope when the number of neutronsvary in the nucleus of a given element(always same number of protons)</p><p> Atomic Number (Z) number of protons</p><p>Section 10.2 Copyright Houghton Mifflin Company. All rights reserved. 10 | 32</p><p>Radioactivity</p><p> Radioactivity (radioactive decay) thespontaneous process of nuclei undergoing achange by emitting particles or rays</p><p> Nuclide a specific type of nucleus 238U or 14C</p><p> Radionuclides (radioactive isotopes orradioisotopes) nuclides whose nucleiundergo spontaneous decay (disintegration)</p><p> Substances that give off such radiation aresaid to be radioactive</p><p>Section 10.3</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 33</p><p>Radioactive Decay</p><p> Parent nucleus the original nucleusbefore decay</p><p> Daughter nucleus (or daughter product) the resulting nucleus after decay</p><p> Radioactive nuclei can decay(disintegrate) in three common ways</p><p> Alpha decay</p><p> Beta decay</p><p> Gamma decay</p><p>Section 10.3 Copyright Houghton Mifflin Company. All rights reserved. 10 | 34</p><p>Radioactive Decay (disintegration)</p><p> Gamma decay occurs when a nucleusemits a gamma ray (g) and becomes aless energetic form of the same nucleus</p><p>Section 10.3</p><p>2</p><p> Alpha decay disintegration of a nucleusinto a nucleus of another element, w/ theemission of an alpha particle (a) - a heliumnucleus (4He)</p><p>-1</p><p> Beta decay a neutron is transformedinto a proton, w/ the emission of a betaparticle (b) an electron ( 0e)</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 35</p><p>Three Components of Radiationfrom Radionuclides</p><p>Section 10.3</p><p>Alpha(a), Beta(b), Gamma(g)</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 36</p><p>Nuclear Decay Equations - Examples</p><p> In a nuclear decay equation, the sums ofthe mass numbers (A) and the sums ofthe atomic numbers (Z) will be theequivalent on each side</p><p>Section 10.3</p><p> Alpha decay = 232Th 228Ra + 4He90</p><p>88 2</p><p> Beta decay = 14C 14N + 0e6 7 -1</p><p> Gamma decay = 204Pb* 204Pb + g82</p><p>82</p></li><li><p>7</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 37</p><p>The Products of Alpha Decay Example</p><p> Must determine the mass number (A), theatomic number (Z), and the chemical symbolfor the daughter product</p><p>Section 10.3</p><p> 238 U undergoes alpha decay. Write the equationfor the process92</p><p> 238 U ?92</p><p> 238 U _??_ + 4He92 2</p><p> 238 U _234_ + 4He92 290</p><p> 238 U _234Th_ + 4He92 290</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 38</p><p>Five Common Forms of Nuclear Radiations</p><p>Section 10.3</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 39</p><p>Decay Series of Uranium-238 to Lead-206</p><p>Section 10.3 Copyright Houghton Mifflin Company. All rights reserved. 10 | 40</p><p>Identifying Radionuclides</p><p> Which nuclides are unstable (radioactive)and which are stable?</p><p> An interesting pattern emerges:</p><p> Most stable nuclides have an even number ofboth protons and neutrons (even-even nuclides)</p><p> Most unstable nuclides have an odd number ofboth protons and neutrons (odd-odd nuclides)</p><p> A nuclide will be radioactive if:</p><p> Its atomic number (Z) is &gt; than 83</p><p>Section 10.3</p><p> n</p></li><li><p>8</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 43</p><p>A Plot of Number of Neutrons (N) Versus Numberof Protons (Z) for the Nuclides</p><p> Showing band ofstability</p><p>Section 10.3 Copyright Houghton Mifflin Company. All rights reserved. 10 | 44</p><p>Half-Life of a Radinuclide</p><p> Half-Life the time it takes for half of thenuclei of a given sample to decay</p><p> In other words after one half-life hasexpired, only one-half of the originalamount of radionuclide remainsundecayed</p><p> After 2 half-lives only one-quarter ( of) of the original amount of theradionuclide remains undecayed</p><p>Section 10.3</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 45</p><p>Decay of Thorium-234 over Two Half-LivesThorium-234 has a Half-Life of 24 days</p><p>Section 10.3 Copyright Houghton Mifflin Company. All rights reserved. 10 | 46</p><p>Decay Curvefor AnyRadionuclide</p><p>Section 10.3</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 47</p><p>Half-Lives of Some Radionuclides</p><p>Section 10.3 Copyright Houghton Mifflin Company. All rights reserved. 10 | 48</p><p>Finding the Number of Half-Livesand the Final Amount</p><p> What fraction and mass of a 40 mg sample ofiodine-131 (half-live = 8d) will remain in 24d?</p><p> Step 2 Start with the given amount No =40mg, and half it 3 times (3 half-lives) Once No/2 = 20 mg (after 8 days)</p><p> Twice No/4 = 10 mg (after 16 days)</p><p> Thrice No/8 = 5 mg (after 24 days)</p><p>Section 10.3</p><p> Step 1 find the number of half-lives that havepassed in 24 days: 24 days = 3 half-lives</p><p>8d/half-life</p></li><li><p>9</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 49</p><p>Finding the Number of Half-Lives and theFinal Amount Confidence Exercise</p><p> What fraction of Stontium-90 produced in1963 (half-live = 29y) will remain in 2021?</p><p> Step 2 Start with the given amount = No After 1 half-life No/2 = (after 29 years)</p><p> After 2 half-lives No /4 = (after 58 years)</p><p>\\ One fourth of the original Strontium-90 remains</p><p>Section 10.3</p><p> Step 1 find the number of half-lives that havepassed in 58 years: 58 years = 2 half-lives</p><p>29y/half-life</p><p>Copyright Houghton Mifflin Company. All rights reserved. 10 | 50</p><p>Finding the Elapsed Time</p><p> How long would it take a sample of 14C todecay to one-fourth its original activity?(half-live of 14C is 5730 years)</p><p> Solution: No No/2 No/4 \14C would</p><p>need to decay for two half-lives in order tobe reduced to its original activity.</p><p> (2 half-lives)(5730 y/half-life) = 11,460years</p><p>Section 10.3</p><p>Copyright Houghton Mifflin Company. All right...</p></li></ul>