Chem. 212 – Molecular Structures and Geometries
Hand in to TA: VSEPR-Pre-lab; Solubility Report, GCF’s.
• Pick up one Model Kit per group.
• Hybridization of carbon
• Follow Sequence of:
Lewis -> AXE -> VSEPR
• Follow format (see later slide)
• methane
• ethane vs. ethene vs. ethyne
• Lab report due next week:
(Tue-Group next Tue 9:30 am); (Wed-Group next Wed 2:00 pm);
(Fri-Group next Thu 12:00 nn).
CyberChem (VSEPR) video
Hybridization of Carbon
Free Carbon
Bonding in Carbon
2p
E
2s
Four Equivalent sp3 Hybridized Orbitals
(Tetrahedral)
 Methane
 Ethane versus Ethene (Geometrical Isomers)
 Ethyne
 Bromochloroiodomethane (Stereoisomers)
Drawing Lewis Structures
1.
2.
3.
4.
5.
6.
Follow Step by Step Method (See Ng Web-site)
Total all valence electrons. [Consider Charge]
Write symbols for the atoms and guess skeleton structure
[ define a central atom ].
Place a pair of electrons in each bond.
Complete octets of surrounding atoms. [ H = 2 only ]
Place leftover electrons in pairs on the central atom.
If there are not enough electrons to give the central atom
an octet, look for multiple bonds by transferring
electrons until each atom has eight electrons around it.
CyberChem video
HyperChem
Summary of VSEPR Molecular Shapes
e-pairs
Notation
Name of VSEPR shape
Examples
2
AX2
Linear
HgCl2 , ZnI2 , CS2 , CO2
3
AX3
Trigonal planar
BF3 , GaI3
AX2E
Non-linear (Bent)
SO2 , SnCl2
AX4
Tetrahedral
CCl4 , CH4 , BF4-
AX3E
(Trigonal) Pyramidal
NH3 , OH3-
AX2E2
Non-Linear (Bent)
H2O , SeCl2
AX5
Trigonal bipyramidal
PCl5 , PF5
AX4E
Distorted tetrahedral
(see-sawed)
TeCl4 , SF4
AX3E2
T-Shaped
ClF3 , BrF3
AX2E3
Linear
I3- , ICl2-
AX6
Octahedral
SF6 , PF6-
AX5E
Square Pyramidal
IF5 , BrF5
AX4E2
Square Planar
ICl4- , BrF4-
4
5
6
HyperChem
CyberChem video
See Ng Web-site
Lewis/AXE/VSEPR Format
Formula/Name
(Total # valence e-)
PF3
phosphorus trifluoride
(26)
Lewis Structure and
AXE Notation
VSEPR 3D Drawing
Name of Shape of all
possible central
atoms