Molecular Models Activity

carbon tetrachloride ammonia

methane hydrogen monochloride

water trichloromethane

ethane urea

ethyne propane

dihydrogen monosulfide butane

carbon dioxide nitrogen triiodide (video)

supplies
 Bonding and Shape of Molecules
Number Number of Covalent
of Bonds Unshared Pairs Structure Shape Examples

2 0 -Be- Linear BeCl2

B
3 0 Trigonal planar BF3

4 0 C Tetrahedral CH4, SiCl4

:

3 1 N Pyramidal NH3, PCl3

:

2 2 O: Bent
H2O, H2S, SCl2
 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
3) Complete octets on exterior atoms (not H, though)
- 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
 Carbon tetrachloride
Cl
Cl
Cl C Cl C
Cl Cl
Cl
109.5o

Cl
CCl4 Tetrahedral geometry

Carbon tetrachloride – “carbon tet” had been used as dry cleaning solvent
because of its extreme non-polarity.
 Methane
H H

H CH C
H H 109.5o H
H
Tetrahedral geometry

Methane –The first member of the paraffin (alkane) hydrocarbons series.

a.k.a. (marsh gas, CH4).
 Water
(-)
.. .. SO2

Bent O
geometry H H
(+)

Polar molecule
 Ethane
C = 1s22s22p2
H H
H C CH
H H
Lewis dot notation ball-and-stick

C2H4
molecular formula

space-filling molecule
 Ethane
H H
H C CH
H H
Lewis dot notation ball-and-stick

C2H6
molecular formula

space-filling molecule
 Ethyne
No octet 6 electrons = triple bond
each C “feels” 6 electrons

H C CH H C CH
Stable octet
C2H2

H C CH
each C “feels” 7 carbons

Ethyne – a.k.a. “acetylene”

Dihydrogen monosulfide
.. .. SO2

S
H H

Bent
 Carbon dioxide

O C O O C O
O C O
Linear
CO2 geometry
 Ammonia
.. ..
N N H
N
NH3 HH H H
H
Trigonal H 107o H
Pyramidal H
geometry
 Amino Acids – Functional Groups

Amine Base Pair Carboxylic Acid

NH21- R- COOH

lose H+ H+
NH21- NH3 NH41+

H 1+

:
:

:
1-

N N N
:

H H H H
H H
H H

+
amine ammonia ammonium ion
 Hydrogen monochloride

H Cl
HCl

(+) (-)
HCl(g) + H2O(l)  HCl(aq)
hydrogen water hydrochloric
chloride acid

Polar molecule
 Trichloromethane

(+)

H
H H
Cl C Cl C Cl C Cl
Cl Cl 109.5o Cl Cl
Cl
CHCl3 (-)
Tetrahedral geometry

Polar molecule
 Urea
NOT “di-urea”

H H
N H N H
O C O C
N N
H H
H H
CO(NH2)2
Urea – The first organic compound to be synthesized (Wohler, 1828).
 Propane
H
H H H H

C C C
H

HC C CH H
H H H
H

H H H

C3H8
 Butane
H H H H H H H H
H C C C CH H-C-C-C-C-H
H H H H H H H H

H H
H H
C4H10 C C C C H
H
H H H H
 Nitrogen triiodide
..
N
I I N
I I 107o I
NI3 I
Trigonal
Pyramidal
geometry

Video clip:

(slow motion)

detonation of NI3
 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
Cl H
Cl C Cl H CH O C O
Cl H CO2

CCl4 CH4

H S
HC CH H H
CH 2 2Cl C Cl SH2

H Cl Cl
CHCl3
HCl
 H H H H H H H
H C C C CH H C C CH
H H H H H H H

N N
H HH I I
I
Decomposition of Nitrogen Triiodide
Decomposition of Nitrogen Triiodide

N2
NI3 I2

2 NI3(s) N2(g) + 3 I2(g)

 H .. ..

C N O
H H H H

..
H 109.5o 107o 104.5o

H H H
CH4, methane NH3, ammonia H2O, water

lone pair ..
electrons

O
O
O O
O O
O3, ozone
 The VSEPR Model
The Shapes of Some Simple ABn Molecules
..
.. .. SO2
O
S N F
O C O O O F
S
F
O O
Linear Bent Trigonal Trigonal
planar pyramidal
AB6

F F
F F F F
F F
Xe P F S
F Cl F
F F F F F

T-shaped Square F F
planar
Trigonal Octahedral
bipyramidal
Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 305
 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 - bonding pieces
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)