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

Bonding and Shape of Molecules Number of Bonds Number of Unshared Pairs ShapeExamples Linear Trigonal planar Tetrahedral Pyramidal Bent BeCl 2 BF 3 CH 4, SiCl 4 NH 3, PCl 3 H 2 O, H 2 S, SCl 2 -Be- B C N : O : : Covalent Structure

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. 3) Complete octets on exterior atoms (not H, though) 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 - no unpaired electrons (free radicals)

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

Methane CH H H H C o H H H H Methane –The first member of the paraffin (alkane) hydrocarbons series. a.k.a. (marsh gas, CH 4 ). Tetrahedral geometry

Water.. HH O Bent geometry SO 2  (-)  (+) Polar molecule

Ethane C H CH H H HH space-filling molecule ball-and-stick Lewis dot notation C2H4C2H4 molecular formula C = 1s 2 2s 2 2p 2

Ethane C H CH H H HH space-filling molecule ball-and-stick Lewis dot notation C2H6C2H6 molecular formula

Ethyne CCHHCCHH No octet Stable octet 6 electrons = triple bond CCHH C2H2C2H2 CCHH each C “feels” 6 electrons each C “feels” 7 carbons Ethyne – a.k.a. “acetylene”

Dihydrogen monosulfide.. HH S Bent SO 2

Carbon dioxide OO C Linear geometry CO O CO 2 CO O

Ammonia N HH H N 107 o H H H.. NH 3.. H H H N Trigonal Pyramidal geometry N HH H

Amino Acids – Functional Groups AmineCarboxylic AcidBase Pair NH 2 1- R- COOH NH 3 NH 2 1- NH 4 1+ amineammoniaammonium ion N H H H : N H H H H : 1+ N H H : 1- : H+H+ lose H +

Hydrogen monochloride HCl HCl HCl  (-)  (+) HCl Polar molecule HCl(g) + H 2 O(l)  HCl(aq) hydrogen chloride water hydrochloric acid

Trichloromethane CCl H CHCl 3 C o H Cl C H  (-)  (+) Polar molecule Tetrahedral geometry

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

Propane C H CH H C H H HHH C C C H H H H H H H H C3H8C3H8

Butane C H CH H C H CH H HHHH H - C - C - C - C - H H H C 4 H 10 C C C H H H H H H H H C H H

Nitrogen triiodide N II I N 107 o I I I.. NI 3 Trigonal Pyramidal geometry Video clip: (slow motion) detonation of N I 3

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

C Cl I S O N H C C H HH H CO O S HH CCHH C H H CCl 4 CH 4 CO 2 C2H2C2H2 HCl CHCl 3 SH 2

C H CH H C H CH H HHHH C H CH H C H H HHH N HH H N II I

Decomposition of Nitrogen Triiodide

2 NI 3 (s) N 2 (g) + 3 I 2 (g) NI 3 I2I2 N2N2

C o H H H H N 107 o H H H.. O o H H.. CH 4, methaneNH 3, ammoniaH 2 O, water.. O O O lone pair electrons O OO O 3, ozone

.. The VSEPR Model OO C Linear The Shapes of Some Simple AB n Molecules OO S Bent OO S O Trigonal planar F F F N Trigonal pyramidal T-shapedSquare planar FF Cl F F F Xe FF F F F P F F Trigonal bipyramidal Octahedral F F F S F F F AB 6 SO 2 Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 305