Bonds
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
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
C=C
CΞC
154 pm
134 pm
120 pm
VSEPR
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.
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.
2 Bonded Atoms 0 Lone Pairs
• Ex: CO2
180°
O C O
• This is a linear shape
• Linear molecules have a bond angle of 180°
3 Bonded Atoms 0 Lone Pairs
• Ex: CH2O
H
120°
C O
H
• This is a trigonal planar shape
• Trigonal planar has a bond angle of 120°
2 Bonded Atoms 1 Lone Pair
• Ex: HNO
●●
N
H 120° O
• This is a bent shape
• This bent has a bond angle of 120°
4 Bonded Atoms 0 Lone Pairs
• Ex: CH4 (AKA methane)
H 109.5°
H C H
H
• This is a tetrahedral shape
• Tetrahedral has a bond angle of 109.5°
3 Bonded Atoms 1 Lone Pair
• Ex: NH3 (AKA ammonia)
●●
H N H
109.5°
H
• This shape is trigonal pyramidal
• Trigonal pyramidal has a bond angle of 109.5°
2 Bonded Atoms 2 Lone Pairs
• Ex: H2O (AKA water)
●●
●●
O H
109.5°
H
• This shape is bent
• This bent has a bond angle of 109.5°
Practice
• Draw the Lewis structure and predict the
shape and bond angle for the following
molecules:
• SiCl4
• SI2
• HCN
• BrPS