Zumdahl�s Chapter 2

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					Zumdahl’s Chapter 2

   Atoms, Molecules, and Ions
Chapter Contents
   History of Chemistry      Periodic Table
   Mass & Proportions            Symbols and
                                   Organization
   Dalton Theory
                              Naming Compounds
   Subatomic Particles
                                  Binary ionic molecule
   Structure of the              Binary covalent
    Atom                           compounds
   Molecules and Ions            Polyatomic ions
History of Chemistry
   Democritus (5th Century BC) atomic
    postulate
   Lucretius (1st Century AD) “atoms and
    the void”
   Priestly (18th Century AD) discovers
    oxygen
   Lavoisier (18th) diamond=carbon
Conservation of Mass and
Chemical Proportions
   Mass unchanged in chemical reactions
   Implies atoms conserved in reactions
   Elements combine in definite, simple
    proportions by mass.
        Molecules are
       atoms in definite
       proportions! - Dalton
John Dalton (1808)
   Elements are collections of identical,
    miniscule atoms.
   Different elements differ in their atoms.
   Compounds are combinations of
    different elements.
   Under reaction, compounds rearrange
    their atoms.
Subatomic Components
   J.J. Thompson (1897) “cathode rays are
    electrons” (e–) and finds e/m ratio
   Robert Millikan (1909) measures e and hence
    melectron known at 9.1110-31 kg
   E. Rutherford (1906) bounces  (He2+) off Au
    tissue proving protons (p+) in nucleus
   F.A. Aston (1919) “weighs” atomic ions
   J. Chadwick (1939) observes neutrons (no
    charge) by decomposition (to p+, e–, and ).
Structure of the Atom
              Nucleons (protons and
               neutrons) of almost the
               same mass (1.6710-27 kg)
               live in nucleus (R~2 fm).
              Electrons occupy the full
               atomic radius (R~50 pm),
               shielding the nucleus.
              Electron and proton count
               identical in neutral atom.
Symbology of an Atom
  79Br       Z=35 is bromine’s atomic
              number (count of protons)
35           A=79 is its mass number
              (count of all nucleons)
             So 3579Br has 79–35 or 44
              neutrons
               81Br exist too in equal #s.
              35
             So isotope average A=80
Molecules and Ions
   Atoms in molecules share (covalent) or
    steal (ionic) electrons to bond.
   Stolen electrons lead to attraction of
    unlike charged ions (ionic bonding)
   Directional electron “clouds” lead to
    molecular shapes.
   Molecules can be ionic as well as atoms.
Periodic Table
                    Z increases linearly
                     from 1H upper left
                    Groups (columns)
                     have similar
                     chemistry
                        Alkali metals,
                         alkaline earths,
                         transition metals,
                         halogens and noble
                         gases
Naming Compounds
   IONIC                            COVALENT
       Cation named first.              Less electronegative
                                          element named first
       If atom 1 makes only
                                          Most electronegative
        one cation:                   
                                          gets “anionic” –ide
            Strontium chloride
             SrCl2                       Greek prefixes show
                                          proportions:
       If atom 1 makes                       Dichlorine heptoxide
        several cations:                       Cl2O7
            Iron(III) chloride               Mono prefix is never
             FeCl3                             used for first atom.
Polyatomic Ions
   Few polyatomic cations
       Most common: ammonium (NH4)+
   Many polyatomic anions
       NO3– nitrate, C2O42– oxalate, HSO4–
        hydrogen sulfate, H2PO4– dihydrogen
        phosphate, Cr2O72– dichromate
       ClO– hypochlorite, ClO2– chlorite, ClO3–
        chlorate, ClO4– perchlorate
Naming Exercise
   Al2(S2O3)3      Aluminum thiosulfate
   P4O10           Tetraphosphorous
                     decaoxide
   Cu(NO2)2        Copper(II) nitrite
   NaMnO4          Sodium permanganate
   CS2             Carbon disulfide
   Fe2(CrO4)3      Iron(III) chromate
   HCl (gas)       Hydrogen chloride
                    Phosphonium bromite
   PH4BrO2

				
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