Catalyst
1.
2.
3.
Thalidomide
Today’s Learning Targets
• LT 2.6 – Using the concept of bond angles and
electron repulsion, I can predict the electron and
molecular geometry of a compound using the
VSPER theory.
• LT 2.7 – Using the molecular geometry of a
compound, I can predict the polarity of a
compound and the direction (if any) of a dipole
moment.
Exploration of Molecular Shapes
• Take out the handout titled “Exploration of
Molecular Shapes”
• Complete with a group member
• Make sure to consider
Lecture 2.4 – VSEPR Theory
VSEPR Theory
• Lewis structures are 2 dimensional drawings,
but atoms bond to form 3 dimensional
molecules.
• Since electrons repel one another, molecules will
bond so as to have the largest bond angle.
▫ If possible, they will be 180o apart.
• This is the foundation of the Valence Shell
Electron Pair Repulsion Theory (VSEPR)
Shape
Picture
Bond Angle
Linear
180o
Trigonal
Planar
120o
Tetrahedral
109.5o
Trigonal
Bipyramidal
120o and 900
Octahedral
900
VSEPR Theory and Lewis Structures
• When examining Lewis structures to determine
shape, we consider electron domains around the
central atom
▫ An electron domain is either a bond or lone pair
found on the central atom.
• The number of electron domains determines
geometry of the electrons around the central
atom.
Molecular Shape
Number of Electron
Domains
Linear
2
Trigonal Planar
3
Tetrahedral
4
Trigonal
Bipyramidal
5
Octahedral
6
Class Example
• Predict the electron domain geometry of CCl4
Table Talk
• Predict the electron domain geometry of BCl3
Molecular Geometry
• Whether an electron domain is in a bond or as a
lone pair on the central atom will impact the
final overall shape of the molecule.
• When determining the final molecular shape,
determine the number of domains as lone pairs
and the number in bonds
Class Example
• Predict the electron domain geometry and the
molecular geometry of NH3
Table Talk
• Determine the electron domain geometry and
the molecular geometry of H2O
Table Talk
• Determine the electron domain geometry and
the molecular geometry of the following two
molecules:
▫ SF4
▫ IF6
Dipole Moments and VSEPR Theory
• The dipole moment of a molecule changes when
the molecular structure is considered.
• For molecules of 2+ atoms, the dipole moment
depends on:
1. The polarity of the bond
2. The geometry of the molecule
Class Example
• Determine the dipole moment of CO2
Class Example
• Determine the dipole moment of H2O
Table Talk
• Determine the dipole moment of CCl4
Table Talk
• Determine the dipole moment of CH3Cl
Summarize
Race to the Finish!
• With your partner, you need to complete the grid
you picked up on your way into class.
• The molecules you need to answer for are
around the room.
• First group to finish with the correct answers
gets 5 EC points for their next exam.
Closing Time
• Do questions from section 9.1 to 9.3 and read
remainder of chapter 9 for Monday/Tuesday
• AP Lab 4 Pre-lab due at start of class
Monday/Tuesday