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Unit II Atomic History, Theory & Structure Textbook Chapters 3 and 4

Unit II Atomic History, Theory & Structure Textbook Chapters 3 and 4. Image taken from http://www.universetoday.com/wp-content/uploads/2010/02/c-atom_e1.gif on 8/8/11. How small is small?. Greeks “Atomos” Democritus 430 B.C. Continuous vs. Discontinuous Theory of Matter.

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Unit II Atomic History, Theory & Structure Textbook Chapters 3 and 4

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  1. Unit II Atomic History, Theory & Structure Textbook Chapters 3 and 4 Image taken from http://www.universetoday.com/wp-content/uploads/2010/02/c-atom_e1.gif on 8/8/11.

  2. How small is small? • Greeks “Atomos” • Democritus 430 B.C. • Continuous vs. Discontinuous Theory of Matter Image taken from http://www.universetoday.com/wp-content/uploads/2009/12/Democritus.jpg on 8/8/11.

  3. 3 Laws that Support Existence of Atoms • The Law of Definite Proportions • The Law of Conservation of Mass • The Law of Multiple Proportions Image taken from http://nuweb.neu.edu/bmaheswaran/phyu121/data/ch09/fig09.htm on 8/8/11. Image taken from http://wikis.lawrence.edu/display/CHEM/1++Laura+Qiu on 8/8/11.

  4. John Dalton’s Atomic Theory (1808) • All matter is composed of extremely small particles called atoms, which cannot be subdivided, created or destroyed. Image taken from http://www.elmhurst.edu/~chm/vchembook/101Aatoms.html on 8/8/11.

  5. Dalton’s Atomic Theory Continued 2. Atoms of a given element are identical in their physical and chemical properties.

  6. Dalton’s Atomic Theory Continued 3. Atoms of different elements differ in their physical and chemical properties. Image taken from http://www.wired.com/images/article/full/2008/09/Dalton_atomic_symbols.jpg on 8/8/11.

  7. Dalton’s Atomic Theory Continued 4. Atoms of different elements combine in simple, whole-number ratios to form compounds. Image taken from http://www.physicalgeography.net/fundamentals/images/compounds_molecules.jpg on 8/8/11.

  8. Dalton’s Atomic Theory Continued 5. In chemical reactions, atoms are combined, separated or rearranged but never created, destroyed or changed. Image taken from http://www.personal.kent.edu/~cearley/ChemWrld/balance/H2_O2.gif on 8/8/11.

  9. My Gosh! Atoms are Divisible. • J.J. Thomson (1897) • Discovers electrons with cathode ray tube experiment. • “Plum pudding” or “Chocolate chip cookie” atomic model Positive atom with negative charges embedded throughout CRT Video 1906 Nobel Prize winner Image taken from http://nobelprize.org/nobel_prizes/physics/laureates/1906/thomson.jpg on 8/8/11. Image taken from http://www.kentchemistry.com/links/AtomicStructure/plum.gif on 8/8/11.

  10. Millikan’s Oil Drop Experiment • American Robert Millikan, 1909. • Determined the mass of an e-. • e- mass found to be 9.11 X 10-28g Image taken from http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH07/FG07_04.JPG on 8/8/11. Image taken from http://nobelprize.org/nobel_prizes/physics/laureates/1923/millikan.jpg on 8/8/11.

  11. Bye Plum Pudding, Hello Solar System Model 1908 Nobel Prizewinner • Ernest Rutherford (1911) • Former student of Thomson. • Designed “gold foil” experiment • Conclusions • Most of atom is empty space. • Mass of atom is concentrated in very, very small dense center (nucleus). • Nucleus has a positive charge. Image taken from http://nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford.jpg on 8/8/11. Gold Foil animation Relative size animation Image taken from http://web.neo.edu/rjones/Pages/1014new/Lecture/chemistry/chapter_8/images/rutherford_model.jpg on 8/8/11. Image taken from http://www.rsc.org/chemsoc/timeline/graphic/1911_gfoil_02.jpg on 8/8/11.

  12. Subatomic Particles (Ref Table O) • An atomic mass unit (amu)= 1/12 the mass of 12C atom

  13. What subatomic particles have mass? • Nucleons-subatomic particles (protons & neutrons) containing mass found in nucleus • Atomic Number (Z)-equal to # of protons in nucleus of an atom. • Mass Number (A)-equal to # of nucleons in an atom. Neutron Discovered (1932) by James Chadwick. Won 1935 Nobel Prize. # of neutrons= A-Z Image taken from http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick.jpg on 8/8/11. Englishman Henry Moseley first determined atomic numbers of the elements by using x-rays. Image taken from http://www.windows2universe.org/physical_science/physics/atom_particle/atomic_mass_number_sm.gifon 8/8/11.

  14. Isotopes • Atoms with the same atomic # but different # of neutrons • Affects mass. • For a given element, # of protons is always constant, # of neutrons may vary. Image taken from http://earthguide.ucsd.edu/virtualmuseum/images/raw/LO_Fig6_1_2.jpg on 8/8/11.

  15. Atomic Mass • Different than Mass Number • The weighted average mass of the naturally occuring isotopes of an element. • Listed on Periodic Table (PT) Try an example: Neon-20 90.92% Neon-21 0.257% Neon-22 8.82% Image taken from http://sulfur.nigc.ir/sulfurfacts-isotopes-en.html on 8/8/11.

  16. 12.0111 C 6 2-4 Duality of Atomic Mass • Use Atomic Mass from PT. • Remember Atomic Mass can be measured in either amu’s or grams. • If grams, then gram atomic mass (mass of one mole of atoms of that element). • If amu’s, then weighted avg.atomic mass (mass of one atom of that element). • Example: Image taken from http://www.the-engagement-ring-guide.com/images/what-is-a-diamond.jpg on 8/8/11.

  17. Mass Spectrometer • Instrument that separates isotopes of an element based on differences in their mass. Image taken from http://www.mhhe.com/physsci/chemistry/carey/student/olc/graphics/carey04oc/ch13/figures/1334.gif on 8/8/11.

  18. Electrons • If atom is neutral, e- = • p+ • If not, have an ion. • Ion- a charged atom. • Lose electron(s) form positive ion (cation). • Gain electron(s) form negative ion (anion). • Which ions do metals form? Nonmetals? Super Cation Concept Map Review Image taken from http://usd388.k12.ks.us/highschool/faculty/david_wildeman/Ch.%203%20-%20Earth%20Science.htm on 8/8/11.

  19. First Ionization Energy • Amount of energy needed to remove the most loosely bound electron from an atom. • Reference Table S • Removal of additional e- from an ion becomes more difficult due to imbalance between positive nuclear charge and remaining electrons. • What happens to ionization energy as you go down a group on the PT? Why? • How about when you go left to right across a period on the PT? Why? • Metals? Nonmetals? Image taken from http://websites.pdesas.org/jvogus/2010/5/18/44324/page.aspx on 8/8/11.

  20. Ionic Radius • Metals • Small # of valence e- • Lose e- to form ion • Ionic radius is smaller than atomic radius. • Nonmetals • Large # of valence e- • Gain e- to form ion • Ionic radius is larger than atomic radius. Image taken from http://www.uwec.edu/boulteje/Boulter103Notes/23October.htm on 8/8/11.

  21. Bohr Model of Atom • Neils Bohr (1913) • Electrons orbit nucleus in distinct energy levels or electron shells (1-7 or K-Q). • Energy levels are not flat paths but instead approximations of electron position. 1922 Nobel Prize Winner Image taken from http://nobelprize.org/nobel_prizes/physics/laureates/1922/bohr.jpg on 8/8/11. Hydrogen atom animation Image taken from http://images.tutorvista.com/content/atom/neils-bohr-model-atom.gifon 8/9/11.

  22. I’m so Excited this is not Bohring!!! • Ground State- Electrons are in lowest available energy level. • Excited State- Electrons absorb energy and shift to higher energy level. • Become unstable, so…… • Fall back to ground state and release energy that is a difference between the 2 energy levels (Quanta) Image taken from http://library.thinkquest.org/19662/images/eng/pages/model-bohr-2.jpg on 8/9/11.

  23. Quantum Leap • Quantum (plural Quanta): • Discrete amount of energy that is absorbed or released by electron. • Quanta are also called photons. Image taken from http://library.thinkquest.org/C006669/media/Chem/img/bohr.gif on 8/9/11. Animation

  24. Lyman series • emits photons of UV. • e- drops to n=1. • Balmer series • emits photons of visible light. • e- drops to n=2. • Paschen series • emits photons of infrared. • e- drops to n=3. Image taken from http://outreach.atnf.csiro.au/education/senior/astrophysics/images/spectra/bohrhydrogen.gif on 8/9/11. Electromagnetic Spectrum Balmer Series illustration

  25. Spectral Lines • Electrons in excited state return to ground state. • Emit energy. • Quanta of radiant energy emitted has a characteristic wavelength and frequency. We can measure the wavelength or observe as a different color. • Applications: • Fluorescent lights, fireworks, neon lights, flame tests Image taken from http://www.astronomyknowhow.com/pics-res/hydrogen-spectra.jpg on 8/9/11.

  26. Types of Spectra • Bright line (explained) • Absorption • Spectroscope- instrument used to observe spectra. Image taken from http://www.scitechantiques.com/spectroscope_move/SourceSpectroscopeV3.jpg on 8/9/11. Image taken from http://teachers.bcps.org/teachers_sec/jsmith10/images/F8CE172A0F6B441C833A9A0E5E9D7830.jpg on 8/9/11.

  27. Problems with Bohr’s Model • Worked well for H but not larger atoms. • e- follow quantum or wave mechanics, not classic mechanics. • Max Planck(1900)light acts like both a particle and also a wave, EM energy is quantized. • Louis de Broglie(1927) e- can act like waves. • Werner Heisenberg(1927)Uncertainty principle (can’t be certain of both location & velocity of e-) • Heisenberg and Erwin Schrodingere- is bound to nucleus in manner similar to standing wave.

  28. Image taken from http://www.scienceclarified.com/images/uesc_02_img0063.jpg on 8/8/11.

  29. If I have seen further, it is only by standing on the shoulders of giants.-Issac Newton 1676 Image taken from http://www.notablebiographies.com/images/uewb_07_img0519.jpg on 8/8/11.

  30. Alignment of Platinum atoms within a crystal. Image was taken with a Scanning Tunneling Microscope from http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Graphics/IBMPlatinum.jpe on 8/2/11.

  31. Modern Model(Atomic Orbital/Electron Cloud/Wave-Mechanical) • Can not be precise about e- location. • Electrons occupy orbitals. • Orbitalsaverage region of the most probable e- location. • Orbitals differ in shape, size and orientation in space. Electron Cloud Animation Image taken from http://www.webelements.com/nexus/sites/default/files/images/orbitron-d.jpgon 8/9/11.

  32. Modern Quantum Model • To define the region where electrons are found, scientists assign 4 Quantum numbers (n,ℓ,mℓ,ms). • To explain the 4 Quantum numbers, I will use a Hotel Analogy (H.A.). Placing electrons within the e- cloud is like placing people in a hotel.

  33. The Principal Quantum Number (n) • Principal energy level or shell • Same as the period # on the P.T. for an element. • H.A.- similar to the hotel floor. Maximum # of e- per energy level = 2n2 Image taken from http://wiki.openeducationproject.info/images/1/1c/Orbitals.jpg on 8/9/11.

  34. The 2nd Quantum Number (ℓ) Angular Momentum Quantum Number (ℓ) • Sublevels • s, p, d, f • (lowesthighest energy) • # of sublevels for each principal energy level = # of that principal energy level • H.A.-Wings of rooms on a floor. ** n can be higher than 4 but the sublevels do not get higher than f

  35. The 3rd Quantum Number (mℓ) Magnetic Quantum Number (mℓ) • Orbitals (H.A. the rooms) • Each sublevel may consist of one or more orbitals with each orbital having a different spatial orientation. • Orbitals contain electrons. Use a box to notate. • No more than 2 e- in an orbital.

  36. s sublevel  1 orbital • p sublevel  3 orbitals • d sublevel  5 orbitals • f sublevel  7 orbitals Image taken from http://www.emc.maricopa.edu/faculty/farabee/biobk/orbitals.gif on 8/9/11.

  37. 4th Quantum number (ms) Spin Quantum number (ms) • Spin of the electron • In order for 2 electrons to occupy the same orbital, must have opposite spins. • To notate, use arrows in the box (orbital). • H.A.-One bed can fit 2 people, must sleep opposite, head to toe, toe to head. Image taken from http://www.brooklyn.cuny.edu/bc/ahp/LAD/C3/graphics/C3_quant_04.gif on 8/9/11.

  38. Electron Configuration Rules • No more than 2 e- can be in an orbital. (Pauli exclusion principle, 1925). • Added e- is placed in unfilled orbital of lowest energy.(The Aufbau principle). • 2 e- in an orbital have opposite spins. • In a given sublevel, a 2nd e- is not added to an orbital until each orbital in the sublevel contains one e- (Hund’s Rule of Maximum Multiplicity). Image taken from http://wps.prenhall.com/wps/media/objects/1054/1079855/IMAGES/AAALUMY0.jpg on 8/9/11.

  39. Electron Configuration and Notation Examples • Superscript following each sublevel = # of e- in that sublevel. • Try examples: • Cl • Zr Image taken from http://wps.prenhall.com/wps/media/objects/1054/1079855/IMAGES/AAALUMY0.jpg on 8/9/11. Image taken from http://chemfionaflora.blogspot.com/2011_05_01_archive.html on 8/9/11.

  40. How to remember the sublevel overlap at higher energy levels? • Diagonal Rule for Electron Configuration • Number 1-7 vertically on paper in 4 columns. • Write s2, p6, d10,f14 after the #’s. • Draw in first 2 arrows then add rest diagonally. Elec.Config animation Image taken from http://abacus.bates.edu/acad/depts/biobook/spdf.bmp on 8/9/11.

  41. Valence Electrons • e-’s in the outermost principal energy level of an atom (“The Penthouse Electrons”) • Look at Group #, (1,2,13-18) PT • Important in chemical properties, behavior and bonding. Image taken from http://hyperphysics.phy-astr.gsu.edu/hbase/solids/imgsol/valen.gifon 8/9/11.

  42. Valence Electrons & Stability • We will learn in the next unit that atoms bond to become stable. • Stability is achieved when the s and p orbitals are complete (8 valence e-). • Noble gases already have a stable octet (8 valence e-) and therefore do not readily bond. Exception is Helium w/ 2 in valence. Image taken from http://www.chemistryland.com/CHM130W/11-Bonds/Octet.jpg on 8/9/11.

  43. Kernel • All parts of an atom except valence e- • Nucleus and inner e- Lewis Electron Dot Diagrams • Kernel=Symbol • Valence electrons=dots Image taken from http://academic.brooklyn.cuny.edu/biology/bio4fv/page/oxygen-atom.JPG on 8/9/11.

  44. Atomic Radius • Half the distance between adjacent atoms or • Distance from the nucleus to the valence e- Image taken from http://www.tutorvista.com/content/science/science-ii/periodic-classification-elements/trends.phpon 8/9/11.

  45. Atomic Radius continued • Ref Table S • What happens to the atomic radius as you go down a group on the PT? Why? • How about left to right within a period of the PT? Why? Both images taken from http://www.tutorvista.com/content/science/science-ii/periodic-classification-elements/trends.php on 8/9/11.

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