shapes of covalent molecules
DESCRIPTION
Its sexayyy.TRANSCRIPT
Shapes of Covalent Molecules
By Chris Johnston
Regular Covalent Molecules
CO
OCO2 – Carbon Dioxide
C
HH H
HCH4 - MethaneC OO C
H
HH
H
Figuring out the Shape of a Regular Covalent Molecule
1. In the Bond, pick out the ‘main’ atom and work out how many electrons it has in the outer energy
level.
Cl4C
C1 12 23 34 4
Figuring out the Shape of a Regular Covalent Molecule
2. Draw out a completed dot and cross diagram ofthe molecule to make sure there are no lone pairs
of electrons. Also count the number of bonded pairs.
C
Cl
Cl
Cl
ClLone Pairs:
Bonded Pairs:
0
01234
Figuring out the Shape of a Regular Covalent Molecule
3. Using the number of bonded pairs, find outthe shape of the regular molecule.
No. of Bonded Pairs
Name of Shape
3D Shape 2D Shape + Example
Bond Angles.
2 LinearC OO
CO2180°3 Trigonal
PlanarB
F
F
FBF3
120°4 Tetra-hedral
C
H
HH
H
CH4
109.5°5 TrigonalBipyramidal
PCl
Cl
Cl
Cl
Cl
PCl5
90°+
120°6 Octahedral
S
F
FF
F
F
F
SF6
90°
CCl4
CC
Cl
Cl
Cl
ClC
Cl
ClCl
Cl
109.5°
Irregular Covalent Molecules
OH
H
H2O - Water
NH
H
H
NH3 - Ammonia
NH
HH
O
H H
Figuring out the Shape of an Irregular Covalent Molecule
1. In the Bond, pick out the ‘main’ atom and work out how many electrons it has in the outer energy
level.
Cl3P
P1 12 2334 45 5
Figuring out the Shape of an Irregular Covalent Molecule
2. Draw out a completed dot and cross diagram ofthe molecule and count the number of bonded and lone
pairs of electrons.
P
Cl
Cl Cl Lone Pairs:
Bonded Pairs:
0
0123
1
Figuring out the Shape of an Irregular Covalent Molecule
3. Use the total number of pairs to figure out what shape it is based on, then place the lone pair of
electrons.Total Pairs = Bonded Pairs + Lone Pairs
Total Pairs = 3 + 1
Total Pairs = 4
PCl
ClCl
Figuring out the Shape of an Irregular Covalent Molecule
4. Use the angle of the regular shape, and the number of lone pairs, to figure out the new bond
angle.
XX X
Strength of Repulsion
Bonding Angle = Angle of Regular Shape - (Number of lone pairs x 2.5)
PCl
ClCl
109.5° - 2.5° = 107°
Covalent Ions
O- H
OH- - Hydroxide Ion
N -H
HNH2
- - Ammonia Ion
O H[ ]- NHH[ ]-
Figuring out the Shape of a Covalent Ion
1. In the bond, pick out the ‘main’ atom and work out how many electrons it has in its outer energy
level. Keep the charge in mind!
H3 O+
OO+
O+H
H
H
Figuring out the Shape of a Covalent Ion
2. Draw out a completed dot and cross diagram ofthe molecule and count the number of bonded and lone
pairs of electrons.
Lone Pairs:
Bonded Pairs:
0
0123
1
Figuring out the Shape of a Covalent Ion
3. Use the total number of pairs to figure out what shape it is based on, then place the lone pair of
electrons.Total Pairs = Bonded Pairs + Lone Pairs
Total Pairs = 3 + 1
Total Pairs = 4
O+
HH
H
Figuring out the Shape of a Covalent Ion
4. Use the angle of the regular shape, and the number of lone pairs, to figure out the new bond
angle.
Bonding Angle = Angle of Regular Shape - (Number of lone pairs x 2.5)
O+
HH
HBond Angle = 109.5° - 2.5 °
Bond Angle = 107 °