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“Advanced General Chemistry” Chemistry 201 Prof. Gordie Miller Websites: http://avogadro.chem.iastate.edu/chem201/ WebCT: https://webct.its.iastate.edu/ Teaching Assistants: Daping Jing (Sect. 5 & 6; Chem 201L: Sect. 3 & 5) Philip Carlson (Sect. 4; Chem 201L: Sect. 4 & 6) Wednesdays: Sect. 4 in 1801 Gilman; Sect. 5 & 6 in 1114 Gilman Exam Dates: Final: Resources: E-Resources for Chemistry (Library Website) Handbook of Chemistry & Physics (CRC Handbook) Please show respect to your colleagues: Turn off cell phones, put aside the Daily, do not use iPods, laptops, or other devices for messaging, facebook, internet browsing, etc. during lectures and recitations. 1 Department of Chemistry Fall Convocation Friday, August 27, 2010; 2:10 p.m. 1352 Gilman Hall “Atoms, Molecules and Bonds, a Multidisciplinary Journey, 400 B.C. to 2000 A.D.” Prof. Klaus Ruedenberg Department of Chemistry Iowa State University 2 Chemical Fundamentals: Introduction Importance of Chemistry in Our Society • Health Issues: • Energy Issues: Research at ISU Ames Laboratory (US DOE) Catron Center for Solar Energy Research Center for Catalysis Center for Physical and Computational Mathematics Center for Sustainable Environmental Technologies Materials Preparation Center Microelectronics Research Center Midwest Forensics Resource Center • Environmental Issues: Beyond the Molecular Frontier, National Research Council, 2003 3 Chemical Fundamentals: Matter (1) Taxonomy Pure Substances Mixtures 4 Chemical Fundamentals: Matter (2) Scale and States • Nuclear: protons + neutrons • Atomic: nucleus + electrons • Molecular: aggregates of atoms • Nanoscale: oligomers, macromolecules • Microscopic: polymers, small crystals • Macroscopic: bulk materials, powders 5 Chemical Fundamentals: Matter (2) Scale and States Carbon Dioxide • Solids: • Liquids: • Gases: • Plasmas: • Supercritical Fluids: 6 Chemical Fundamentals: Matter (3) Properties of Matter Physical Properties: “Measured without changing the identity of the substance” Chemical Properties: CaC2(s) + H2O(l) CaO(s) + C2H2(g) 2 C2H2(g) + 5 O2(g) 4 CO2(g) + 2 H2O(l) 7 Chemical Fundamentals: Measurements (4) Units SI Units: Seven fundamental quantities 1. 2. 3. 4. 5. 6. 7. Length (Meter) Mass (Kilogram) Time (Second) Temperature (degree Kelvin) Amount (Mole) Electric Current (Ampere) Luminous Intensity (Candela) Density = Energy = 8 Chemical Fundamentals: Measurements (5) Error • Systematic (Determinate) Error • Random (Indeterminate) Error Source: H. Joyce, Millenium Mathematics Project Gaussian Distribution Curve Fitting (Regression) (Propagation of Error) P(x) 0.8 = 0.5 0.6 0.4 = 1.0 0.2 = 2.0 0.0 -6 -4 -2 0 2 4 6 x Mean Value: x Standard Deviation: Source: J. Schreiner, MPI-Kernphysic X. Peng, et al., Nature 404, 59-61(2000) 9 Chemical Fundamentals: Measurements (6) Precision vs. Accuracy Standard Deviation (1) Mean Value =?= True Value (2) (3) 10 Chemical Fundamentals: Measurements (7) Significant Figures For each scale, report the value using the appropriate number of significant figures. 11 Chemical Fundamentals: Atoms, Molecules, … (1) Important Experiments • Faraday’s Experiments: • Thomson’s Experiment: Source: Atom – The Incredible World • Milliken’s Oil-Drop Experiment: Source: Atom – The Incredible World 12 Chemical Fundamentals: Atoms, Molecules, … (1) Important Experiments • Rutherford’s Experiment: Source: Encyclopedia of Science • Stern-Gerlach Experiment: Source: Atom – The Incredible World 13 Chemical Fundamentals: Atoms, Molecules, … (2) Atomic Structure Symbol Mass (g) Charge (coul) Spin (Jsec) Proton 1 1 p 1.672 1024 (1) 1.602 1019 (+1) 5.273 1035 (1/2) Neutron 1 0 n 1.674 1024 (1) 0.000 1019 (0) 5.273 1035 (1/2) Electron 0 1 9.109 1028 (“0”) 1.602 1019 (1) 5.273 1035 (1/2) e • ATOM = • NUCLEUS = Source: Dr. R.F.W. Bader, McMaster University, Canada. 14 Chemical Fundamentals: Atoms, Molecules, … (2) Atomic Structure A Z Sy A Sy Some key consequences: • # Protons (Z) – • # Electrons = Core electrons Valence electrons • # Neutrons Stability of Isotopes # Stable Isotopes Protons Neutrons 157 Even Even Source: www.mc.maricopa.edu/~gilletti/CHM152/NUCLEAR.ppt 53 Even Odd 50 Odd Even 5 Odd Odd 15 Chemical Fundamentals: Atoms, Molecules, … (2) Atomic Structure Stability of Isotopes: Radioactive Decay Alpha emission ( particle = 4He nucleus) Beta emission ( particle = electron) Gamma radiation ( = high energy photons) Positron emission (mass of electron; positive charge) Electron (core) capture 16 Chemical Fundamentals: Atoms, Molecules, … (2) Atomic Structure Stability of Isotopes EB /A Source: http://www.alaskajohn.com/physics/charts/binding_energy.jpg 17 Chemical Fundamentals: Atoms, Molecules, … (2) Atomic Structure Spin: response to a magnetic field E.g. 1H is a single proton (spin = 1/2) Nuclear Magnetic Resonance (MRI) – organic and biomolecules… (Klaus Schmidt-Rohr) 2H (= D, deuterium) is a proton + neutron (spin = 1) has different spin-derived physical properties than 1H Chemical Properties: not significantly affected by isotopes, but … It takes more energy to break an OD chemical bond than an OH bond. Why? HOH vs. DOD 18 Chemical Fundamentals: Atoms, Molecules, … (3) Atomic Mass Standard: 12C atom Mass of 12C atom (6 protons, 6 neutrons, 6 electrons) 1 amu = 1.661 1024 g Many atomic masses are close to integer values, e.g., N (14.007 amu) Ca (40.078 amu) Some are not close to integers, e.g., Why not? Cl (35.453 amu) Isotopes % / (100%) = Isotope Mass 35Cl 37Cl 19 Chemical Fundamentals: Atoms, Molecules, … (3) Atomic Mass GC/LC-MS/MS Mass Spectrometer Source: http://www.epa.gov Source: http://history.nasa.gov 20 Chemical Fundamentals: Atoms, Molecules, … (3) Atomic Mass Intensity of Signal (% Molecules) 60 Mass Spectrum of Cl2 50 Let x = abundance of 35Cl y = abundance of 37Cl 40 30 20 10 0 68 69 70 71 72 73 74 75 76 Mass Number Isotope Abundance 21 Chemical Fundamentals: Atoms, Molecules, … (4) Microscopy: Can we “see” atoms? Electron Microscope To “see” atoms, need light with wavelength ca. 0.1 nm (X-rays) Optical Microscopes: Electron Microscopes: Ames Laboratory, US Department of Energy Wilhelm Hall Advantages: Disadvantages: 22 Chemical Fundamentals: Atoms, Molecules, … (4) Electron Microscopy: SEM vs. TEM Incident e Beam Backscattered e X-rays Cathodaluminescence Secondary e Auger e SAMPLE Inelastically Scattered e Elastically Scattered e Unscattered e 23 Chemical Fundamentals: Atoms, Molecules, … (4) Electron Microscopy: SEM Backscattered e: Incident e Beam Backscattered e X-rays Auger e Secondary e: Cathodaluminescence Secondary e Auger e & X-rays: SAMPLE Factors affecting Image Brightness Al-Cu alloy. 24 Chemical Fundamentals: Atoms, Molecules, … (4) Electron Microscopy: SEM Incident Electron Beam Auger e Secondary e Backscattered e Range of X-rays 25 Chemical Fundamentals: Atoms, Molecules, … (4) Electron Microscopy: TEM Incident e Beam SAMPLE Inelastically Scattered e Elastically Scattered e Elastically scattered e: Unscattered e Inelastically scattered e: 26 Chemical Fundamentals: Atoms, Molecules, … (4) Electron Microscopy: Examples Semiconductor Chip (ca. 100 150 m2) Powder Particle (Quasicrystal: Y-Mg-Zn) ca. 30 m radius Source: ISU Dept. of Materials Science and Engineering 27 Chemical Fundamentals: Atoms, Molecules, … (4) Electron Microscopy: Carbon Nanotubes SEM Images TEM Image ca. 60 80 m2 10 nm inner diameter 9 concentric walls Source: http://www.nano-lab.com/imagegallery.html ca. 1.5 2 m2 (1500 2000 nm2) 28 Chemical Fundamentals: Atoms, Molecules, … (4) Electron Microscopy: Material Issues in Nuclear Reactors Pressurized water in a closed coolant loop carries intense heat generated by fission reactions in nuclear fuel rods (in the reactor core) to steam generators. There, heat is transmitted to water in a separate closed loop to form steam, which drives the turbine (to generate electricity), cools, condenses, and returns to the steam generators. To stainless steel specimens exposed to a nuclear reactor environment, an oxygen weight difference of just 0.04% causes the oxygen-richer material (bottom) to become brittle and pocked with micrometer-sized grains. The other sample retains its structural integrity, as seen in these SEM images. 29 Chemical Fundamentals: Atoms, Molecules, … (4) Microscopy: Imaging Techniques Source: A. B. Ellis, ACS, 1993 30 Chemical Fundamentals: Atoms, Molecules, … (4) Microscopy: Imaging Techniques STM Tip (200 kV incident electrons) Bar length: ca. 20 nm Source: TU-Vienna Source: Purdue Univ. 31 Chemical Fundamentals: Atoms, Molecules, … (4) Microscopy: Imaging Techniques -- STM S8 Source: M.D. Porter, ISU 32 Chemical Fundamentals: Atoms, Molecules, … (4) Microscopy: Imaging Techniques -- Lithography Subsurface H atoms in Pd – PSU arises from Pd atoms rising to make “room” for interstitial H atoms. H atoms find sites by using voltage impulses from an STM tip. Letter height = ca. 0.3 Å; Letter width = ca. 40 Å. Image by: E. H. Sykes, L. Fernandez, B. A. Mantooth, P. Weiss 33 Chemical Fundamentals: Atoms, Molecules, … (4) Microscopy: Improved AFM Capabilities C22H14 Scanning tunneling microscopy (STM) has limited ability to distinguish individual atoms and bonds. In the past, AFM has done no better at resolving atomic-scale features, producing only fuzzy images of individual molecules. CO-tip AFM image (bottom) reveals atoms and bonds of pentacene (top), whereas conventional STM image (center) cannot. Scale bars are 5 Å. Chemical and Engineering News, August 31, 2009, p. 6 Gross, et al. Science 2009, 325, 1110 34 Chemical Fundamentals: Atoms, Molecules, … (5) The Periodic Table H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt 110 111 112 Lanthanides: Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Actinides: Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Metals Metalloids (Semiconductors) Nonmetals 35 Chemical Fundamentals: Atoms, Molecules, … (6) Combining Atoms: Do free atoms exist? H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt 110 111 112 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Aggregates: • Diatomic Molecules • Rings or Chains • Layers • Three-dimensional Nets • Three-dimensional Sphere Packings (Everything else…) 36 Chemical Fundamentals: Atoms, Molecules, … (6) Combining Atoms: Ions Two atoms interact with each other by… (a) (b) H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt 110 111 112 2 1 0 +1 +2 +3 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr “Cations” (net positive charge)… “Anions” (net negative charge)… Polyatomic Ions: 37 Chemical Fundamentals: Atoms, Molecules, … (7) Chemical Formulas (Symbolism) (a) Empirical Formulas – (b) Molecular Formulas – (c) Metallurgical Formulas – (8) Nomenclature: see pages 1-24 to 1-27 in 201 Notes 38