zumdahl’s chapter 2
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Zumdahl’s Chapter 2. Atoms, Molecules, and Ions. History of Chemistry Mass & Proportions Dalton Theory Subatomic Particles Structure of the Atom Molecules and Ions. Periodic Table Symbols and Organization Naming Compounds Binary ionic molecule Binary covalent compounds Polyatomic ions. - PowerPoint PPT PresentationTRANSCRIPT
Zumdahl’s Chapter 2
Atoms, Molecules, and Ions
Chapter Contents History of Chemistry Mass & Proportions Dalton Theory Subatomic Particles Structure of the Atom Molecules and Ions
Periodic Table Symbols and Organization
Naming Compounds Binary ionic molecule Binary covalent compounds 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 9.1110-31 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 (1.6710-27 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
3579Br Z=35 is bromine’s
atomic number (count of protons)
A=79 is its mass number (count of all nucleons)
So 3579Br has 79–35 or
44 neutrons 35
81Br exist too in equal #s.
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
Cation named first. If atom 1 makes only one cation:
Strontium chloride SrCl2 If atom 1 makes several cations:
Iron(III) chloride FeCl3
COVALENT Less electronegative element named
first Most electronegative gets “anionic” –
ide Greek prefixes show proportions:
Dichlorine heptoxide Cl2O7 Mono prefix is never 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, Cr2O7
2– dichromate ClO– hypochlorite, ClO2
– chlorite, ClO3–
chlorate, ClO4– perchlorate
Naming Exercise Al2(S2O3)3 P4O10 Cu(NO2)2 NaMnO4 CS2 Fe2(CrO4)3 HCl (gas) PH4BrO2
Aluminum thiosulfate Tetraphosphorous decaoxide Copper(II) nitrite Sodium permanganate Carbon disulfide Iron(III) chromate Hydrogen chloride Phosphonium bromite