Chemical Bonding
Shapes of Molecules
VSEPR (Valence-Shell Electron-Pair Repulsion Model):
Extends Lewis’s theory of bonding to account for molecular shapes by
adding rules that account for bond angle
Chapter 10 – Chemical Bonding
Rule 1: Regions of high electron concentration (bonds and lone pairs
on the central atom) repel one another and, to minimize
their repulsions, these regions move as far apart as possible
while maintaining the same distance from the central atoms
• Lewis Symbols
• Lewis Structures for Ionic Compounds
• Lewis Structures for Covalent Compounds
• Shapes of Molecules
• Electronegativity and Polarity
• Polar Molecules
1
Rule 2: There is no distinction between single and multiple bonds: a
multiple bond is treated as a single region of high electron
concentration
2
Chemical Bonding
Chemical Bonding
Shapes of Molecules
Shapes of Molecules
Rule 3: All regions of high electron density, lone pairs and bonds,
are included in a description of the electronic arrangement,
but only the positions of atoms are considered when
reporting the shape of a molecule
3
4
Chemical Bonding
Electronegativity and Polarity
5
Variations in the electronegativities of the main group elements
The names of the shapes of simple molecules and their bond angles. Lone pairs of
electrons are not shown.
Chemical Bonding
Chemical Bonding
Lewis Symbols
Lewis Structures for Ionic Compounds
Student Question:
What are the Lewis symbols for Sn, Ga, and Ar?
1
Student Question:
What are the Lewis structures for the following compounds:
LiF
Li2O
2
Chemical Bonding
Chemical Bonding
Lewis Structures for Covalent Compounds
Lewis Structures for Covalent Compounds
Student Question:
What is the Lewis structure for O2?
3
Student Question:
Write the Lewis Structure for each of the following compounds:
N2 H4
C 2 H6
NCl3
4
Chemical Bonding
Chemical Bonding
Lewis Structures for Covalent Compounds
Lewis Structures for Covalent Compounds
Student Question:
Write the Lewis Structure for O3.
5
Student Question:
Assign formal charges on the atoms of the following three ions.
Then identify which structure is the lowest energy structure.
6
Chemical Bonding
Chemical Bonding
Shapes of Molecules
Polar Molecules
Student Question:
Determine the electronic and molecular shape of the following
molecules along with stating the bond angles:
O3
NCl3
7
Student Question:
Determine whether the following molecules are polar or non polar.
H2 S
SiO2
8