1. Bonds

2. Bond Energy Bond Energy: the energy required to break a bond
What type of bond has the highest bond energy?
(Single, Double, or Triple)
C-C 348 kJ
C=C 614 kJ
CΞC 839 kJ

3. Bond Length
Bond Length: the distance between the nuclei of two bonded atoms
What type of bond is the longest?
(Single, Double, or Triple)
C-C 154 pm
C=C 134 pm
CΞC 120 pm

4. VSEPR

5. VSEPR VSEPR: Valence Shell Electron Pair Repulsion
The pairs of valence electrons in a molecule want to be as far apart from each other as possible.
VSEPR allows us to predict the geometry or shape of the molecule.

6. VSEPR
To determine the shape of the molecule you need to count the number of bonded atoms and the number of lone pairs on the center atom of the Lewis structure.
A double or triple bond only counts as 1 bonded atom.

7. 2 Bonded Atoms 0 Lone Pairs
Ex: CO2
This is a linear shape
Linear molecules have a bond angle of 180°
180°
O C O ●●

8. 3 Bonded Atoms 0 Lone Pairs
Ex: CH2O
This is a trigonal planar shape
Trigonal planar has a bond angle of 120° H
C O ●●
120°

9. N H O 2 Bonded Atoms 1 Lone Pair Ex: HNO This is a bent shape
This bent has a bond angle of 120° N
H O ●●
120°

10. 4 Bonded Atoms 0 Lone Pairs
Ex: CH4 (AKA methane)
This is a tetrahedral shape
Tetrahedral has a bond angle of 109.5° H
H C H
109.5°

11. H N H H 3 Bonded Atoms 1 Lone Pair Ex: NH3 (AKA ammonia)
This shape is trigonal pyramidal
Trigonal pyramidal has a bond angle of 109.5°
H N H H ●●
109.5°

12. 2 Bonded Atoms 2 Lone Pairs
Ex: H2O (AKA water)
This shape is bent
This bent has a bond angle of 109.5°
O H H ●●
109.5°

13. Practice
Draw the Lewis structure and predict the shape and bond angle for the following molecules:
SiCl4
SI2
HCN
BrPS