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Molecular Models and Activity: Bonding and Shape of Chemical Molecules

Learn about the covalent structure, shape, and examples of molecules using the VSEPR model and molecular formulas. Understand Lewis structures and the total number of valence electrons, bonds, and unshared pairs in various compounds.

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Molecular Models and Activity: Bonding and Shape of Chemical Molecules

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  1. Molecular Models Activity carbon tetrachloride methane water ethane ethyne dihydrogen monosulfide carbon dioxide ammonia hydrogen monochloride trichloromethane urea propane butane nitrogen triiodide (video) supplies

  2. B : N : : O Bonding and Shape of Molecules Number of Bonds Number of Unshared Pairs Covalent Structure Shape Examples -Be- 0 0 0 1 2 2 3 4 3 2 Linear Trigonal planar Tetrahedral Pyramidal Bent BeCl2 BF3 CH4, SiCl4 NH3, PCl3 H2O, H2S, SCl2 C

  3. Lewis Structures 1) Count up total number of valence electrons 2) Connect all atoms with single bonds - “multiple” atoms usually on outside - “single” atoms usually in center; C always in center, H always on outside. Gilbert Lewis (not H, though) 3) Complete octets on exterior atoms - no unpaired electrons (free radicals) 4) Check - valence electrons match with Step 1 - all atoms (except H) have an octet; if not, try multiple bonds - any extra electrons? Put on central atom

  4. Cl Cl Cl C Cl C Cl Cl Cl 109.5o Cl Carbon tetrachloride Tetrahedral geometry CCl4 Carbon tetrachloride – “carbon tet” had been used as dry cleaning solvent because of its extreme non-polarity.

  5. H H C H H C H H H 109.5o H Methane Tetrahedral geometry Methane –The first member of the paraffin (alkane) hydrocarbons series. a.k.a. (marsh gas, CH4).

  6. .. .. O H H Water d(-) SO2 Bent geometry d(+) Polar molecule

  7. H H C C H H H H Ethane C = 1s22s22p2 ball-and-stick Lewis dot notation C2H4 molecular formula space-filling molecule

  8. H H C C H H H H Ethane ball-and-stick Lewis dot notation C2H6 molecular formula space-filling molecule

  9. 6 electrons = triple bond C C C C H H H H H H H C C H Ethyne No octet each C “feels” 6 electrons Stable octet C2H2 C C each C “feels” 7 carbons Ethyne – a.k.a. “acetylene”

  10. .. .. S H H Dihydrogen monosulfide SO2 Bent

  11. C C O O O O Carbon dioxide O C O Linear geometry CO2

  12. .. .. N H H H N H H 107o H N H H H Ammonia N H H NH3 H Trigonal Pyramidal geometry

  13. : H : 1+ 1- N : N H H H H H Amino Acids – Functional Groups Amine Base Pair Carboxylic Acid R- COOH NH21- lose H+ H+ H+ NH21- NH3 NH41+ : N H H H H + amine ammonia ammonium ion

  14. H Cl H H Cl Cl hydrogen chloride hydrochloric acid water Hydrogen monochloride HCl d(-) d(+) HCl(g) + H2O(l)  HCl(aq) Polar molecule

  15. H H H Cl Cl C C Cl Cl C Cl Cl Cl Cl 109.5o Cl Trichloromethane d(+) CHCl3 d(-) Tetrahedral geometry Polar molecule

  16. O Urea NOT “di-urea” H H H H N N O C C N N H H H H CO(NH2)2 Urea – The first organic compound to be synthesized (Wohler, 1828).

  17. H H H C C C H H H H H Propane H H H C C C H H H H H C3H8

  18. H H H H C C C C H H H H H H Butane H H H H H - C - C - C - C - H H H H H H H H H C4H10 H C C C C H H H H H

  19. .. N I I 107o I Nitrogen triiodide N I I I NI3 Trigonal Pyramidal geometry Video clip: (slow motion) detonation of NI3

  20. Supplies • 15 black (carbon) • 8 green (chlorine and iodine) • 1 yellow (sulfur) • 4 blue (oxygen) • 4 red (nitrogen) • 42 hydrogen (hydrogen) • 67 bonds (bonds)

  21. Cl H H C O Cl Cl C C C H H H Cl Cl Cl H H O H H Cl Cl S C C H C S Cl N I O H CO2 CH4 CCl4 C2H2 SH2 CHCl3 HCl

  22. H H H H H H H C C C C C C C H H H H H H H H H H H N N I I H H H I

  23. Decomposition of Nitrogen Triiodide

  24. Decomposition of Nitrogen Triiodide N2 NI3 I2 2 NI3(s) N2(g) + 3 I2(g)

  25. .. H N C H H H H 107o 109.5o H H O O O O O O O3, ozone .. O H .. 104.5o H CH4, methane NH3, ammonia H2O, water .. lone pair electrons

  26. .. .. .. S O O O C O O S N F O O F F F F F F F F F F P S Xe F F F F F Cl F F F F F The VSEPR Model The Shapes of Some Simple ABn Molecules SO2 Linear Bent Trigonal planar Trigonal pyramidal AB6 T-shaped Square planar Trigonal bipyramidal Octahedral Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 305

  27. Resources - Nomenclature Objectives General Chemistry PP Worksheet - binary cmpds: single charge cation Worksheet - binary compounds Worksheet - ions in chemical formulas Worksheet - ions in chemical compounds Worksheet - ionic cmpds: polyatomic ions w multiple-charge cation Worksheet - ionic formulas (binary, polyatomic, transition) Worksheet - empirical and molecular Worksheet - traditional system of nomenclature Worksheet - vocab (bonding) Worksheet - covalent binary cmpds: non-metal - non-metal Worksheet - ionic cmpds: polyatomic ions Activity - bondingpieces Worksheet - ionic binary cmpds: multiple charge cation Activity - molecular models Worksheet - errors in chemical formulas and nomenclature Activity - mole pattern Worksheet - oxidation numbers and ionic cmpds Textbook - questions Worksheet - names and formulas of cmpds Outline(general)

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