Shapes of molecules

Июль 28, 2022

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Shapes of molecules

Содержание

2. INTRODUCTION This Powerpoint show is one of several produced to help students understand selected topics at
3. CONTENTS Prior knowledge Electron pair repulsion theory The regular molecular shapes Shapes of molecules with lone
4. Before you start it would be helpful to… know the definition of a covalent bond know
5. ELECTRON PAIR REPULSION THEORY “THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR ION IS THAT WHICH
6. ELECTRON PAIR REPULSION THEORY “THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR ION IS THAT WHICH
7. REGULAR SHAPES Molecules, or ions, possessing ONLY BOND PAIRS of electrons fit into a set of
8. BERYLLIUM CHLORIDE Beryllium - has two electrons to pair up Chlorine - needs 1 electron for
9. BERYLLIUM CHLORIDE BOND PAIRS 2 LONE PAIRS 0 BOND ANGLE... SHAPE... 180° LINEAR Beryllium - has
10. ADDING ANOTHER ATOM - ANIMATION
11. Al ALUMINIUM CHLORIDE Aluminium - has three electrons to pair up Chlorine - needs 1 electron
12. Al ALUMINIUM CHLORIDE Cl Cl Al 120° Cl BOND PAIRS 3 LONE PAIRS 0 BOND ANGLE...
13. Al ALUMINIUM CHLORIDE Cl Cl Al 120° Cl BOND PAIRS 3 LONE PAIRS 0 BOND ANGLE...
14. ADDING ANOTHER ATOM - ANIMATION
15. METHANE Carbon - has four electrons to pair up Hydrogen - 1 electron to complete shell
16. METHANE BOND PAIRS 4 LONE PAIRS 0 BOND ANGLE... SHAPE... 109.5° TETRAHEDRAL Carbon - has four
17. METHANE BOND PAIRS 4 LONE PAIRS 0 BOND ANGLE... SHAPE... 109.5° TETRAHEDRAL Carbon - has four
18. PHOSPHORUS(V) FLUORIDE P Phosphorus - has five electrons to pair up Fluorine - needs one electron
19. PHOSPHORUS(V) FLUORIDE P BOND PAIRS 5 LONE PAIRS 0 BOND ANGLE... SHAPE... 120° & 90° TRIGONAL
20. SULPHUR(VI) FLUORIDE Sulphur - has six electrons to pair up Fluorine - needs one electron to
21. SULPHUR(VI) FLUORIDE BOND PAIRS 6 LONE PAIRS 0 BOND ANGLE... SHAPE... 90° OCTAHEDRAL Sulphur - has
22. SULPHUR(VI) FLUORIDE BOND PAIRS 6 LONE PAIRS 0 BOND ANGLE... SHAPE... 90° OCTAHEDRAL Sulphur - has
23. IRREGULAR SHAPES If a molecule, or ion, has lone pairs on the central atom, the shapes
24. AMMONIA Nitrogen has five electrons in its outer shell It cannot pair up all five -
25. AMMONIA ANGLE... 107° SHAPE... PYRAMIDAL H H N H The shape is based on a tetrahedron
26. AMMONIA
27. WATER Oxygen has six electrons in its outer shell It cannot pair up all six -
28. ANGLE... 104.5° SHAPE... ANGULAR H O H H O H 104.5° H O H The shape
29. XENON TETRAFLUORIDE Xenon has eight electrons in its outer shell It pairs up four of its
30. XENON TETRAFLUORIDE F F F F Xe ANGLE... 90° SHAPE... SQUARE PLANAR As the total number
31. CALCULATING THE SHAPE OF IONS The shape of a complex ion is calculated in the same
32. SHAPES OF IONS Draw outer shell electrons of central atom EXAMPLE
33. SHAPES OF IONS NH4+ NH2- Draw outer shell electrons of central atom For every positive charge
34. SHAPES OF IONS NH4+ NH2- Draw outer shell electrons of central atom For every positive charge
35. SHAPES OF IONS NH4+ NH2- BOND PAIRS 4 LONE PAIRS 0 TETRADHEDRAL H-N-H 109.5° BOND PAIRS
36. SHAPES OF IONS BOND PAIRS 3 PYRAMIDAL LONE PAIRS 1 H-N-H 107° BOND PAIRS 4 TETRAHEDRAL
37. MOLECULES WITH DOUBLE BONDS C O O Carbon - needs four electrons to complete its shell
38. MOLECULES WITH DOUBLE BONDS C O O Carbon - needs four electrons to complete its shell
39. OTHER EXAMPLES BrF5 BOND PAIRS 5 LONE PAIRS 1 ‘UMBRELLA’ ANGLES 90° F F F F
40. ANSWERS ON NEXT PAGE TEST QUESTIONS For each of the following ions/molecules, state the number of
41. TEST QUESTIONS 3 bp 0 lp 120º trigonal planar boron pairs up all 3 electrons in
42. REVISION CHECK What should you be able to do? Recall the theory of Electron Pair Repulsion
43. You need to go over the relevant topic(s) again Click on the button to return to
44. WELL DONE! Try some past paper questions
46. Скачать презентацию

Слайд 2

INTRODUCTION
This Powerpoint show is one of several produced to help students

understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications but is suitable for other examination boards.
Individual students may use the material at home for revision purposes or it may be used for classroom teaching if an interactive white board is available.
Accompanying notes on this, and the full range of AS and A2 topics, are available from the KNOCKHARDY SCIENCE WEBSITE at...
www.knockhardy.org.uk/sci.htm
Navigation is achieved by...
either clicking on the grey arrows at the foot of each page
or using the left and right arrow keys on the keyboard

SHAPES OF MOLECULES

KNOCKHARDY PUBLISHING

Слайд 3

CONTENTS
Prior knowledge
Electron pair repulsion theory
The regular molecular

shapes
Shapes of molecules with lone pairs
Shapes of ions
Molecules with double bonds
Other examples
Test questions
Check list

SHAPES OF MOLECULES

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Before you start it would be helpful to…
know the definition

of a covalent bond
know what a lone pair is
know that like charges repel

SHAPES OF MOLECULES

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ELECTRON PAIR REPULSION THEORY
“THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR

ION IS THAT WHICH KEEPS REPULSIVE FORCES TO A MINIMUM”

Molecules contain covalent bonds. As covalent bonds consist of a pair of electrons, each bond will repel other bonds.

Bonds are further apart so repulsive forces are less

Bonds are closer together so repulsive forces are greater

All bonds are equally spaced out as far apart as possible

Bonds will therefore push each other as far apart as possible to reduce the repulsive forces.
Because the repulsions are equal, the bonds will also be equally spaced

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ELECTRON PAIR REPULSION THEORY
“THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR

ION IS THAT WHICH KEEPS REPULSIVE FORCES TO A MINIMUM”

MOLECULES WITHOUT LONE PAIRS

MOLECULES WITH LONE PAIRS

Because of the equal repulsive forces between bond pairs, most simple molecules, (ones with a central atom and others bonded to it), have standard shapes with equal bond angles.
However, the presence of lone pairs on the central atom affects the angle between the bonds and thus affects the shape.

All bonds are equally spaced out as far apart as possible to give minimum repulsive forces

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REGULAR SHAPES
Molecules, or ions, possessing ONLY BOND PAIRS of electrons fit

into a set of standard shapes. All the bond pair-bond pair repulsions are equal.
All you need to do is to count up the number of bond pairs and chose one of the following examples...

2 LINEAR 180º BeCl2
3 TRIGONAL PLANAR 120º AlCl3
4 TETRAHEDRAL 109.5º CH4
5 TRIGONAL BIPYRAMIDAL 90º & 120º PCl5
6 OCTAHEDRAL 90º SF6

BOND BOND
PAIRS SHAPE ANGLE(S) EXAMPLE

A covalent bond will repel another covalent bond

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BERYLLIUM CHLORIDE
Beryllium - has two electrons to pair up
Chlorine - needs

1 electron for ‘octet’

Two covalent bonds are formed
Beryllium still has an incomplete shell

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BERYLLIUM CHLORIDE
BOND PAIRS 2
LONE PAIRS 0
BOND ANGLE...
SHAPE...
180°
LINEAR
Beryllium - has two electrons to pair

up
Chlorine - needs 1 electron for ‘octet’

Two covalent bonds are formed
Beryllium still has an incomplete shell

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ADDING ANOTHER ATOM - ANIMATION

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Al
ALUMINIUM CHLORIDE
Aluminium - has three electrons to pair up
Chlorine - needs

1 electron to complete ‘octet’
Three covalent bonds are formed; aluminium still has an incomplete outer shell.

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Al
ALUMINIUM CHLORIDE
Cl
Cl
Al
120°
Cl
BOND PAIRS 3
LONE PAIRS 0
BOND ANGLE...
SHAPE...
120°
TRIGONAL PLANAR
Aluminium - has three electrons to

pair up
Chlorine - needs 1 electron to complete ‘octet’
Three covalent bonds are formed; aluminium still has an incomplete outer shell.

Слайд 13

Al
ALUMINIUM CHLORIDE
Cl
Cl
Al
120°
Cl
BOND PAIRS 3
LONE PAIRS 0
BOND ANGLE...
SHAPE...
120°
TRIGONAL PLANAR
Aluminium - has three electrons to

pair up
Chlorine - needs 1 electron to complete ‘octet’
Three covalent bonds are formed; aluminium still has an incomplete outer shell.

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ADDING ANOTHER ATOM - ANIMATION

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METHANE
Carbon - has four electrons to pair up
Hydrogen - 1 electron

to complete shell

Four covalent bonds are formed
C and H now have complete shells

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METHANE
BOND PAIRS 4
LONE PAIRS 0
BOND ANGLE...
SHAPE...
109.5°
TETRAHEDRAL
Carbon - has four electrons to pair up
Hydrogen

- 1 electron to complete shell

Four covalent bonds are formed
C and H now have complete shells

Слайд 17

METHANE
BOND PAIRS 4
LONE PAIRS 0
BOND ANGLE...
SHAPE...
109.5°
TETRAHEDRAL
Carbon - has four electrons to pair up
Hydrogen

- 1 electron to complete shell

Four covalent bonds are formed
C and H now have complete shells

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PHOSPHORUS(V) FLUORIDE
P
Phosphorus - has five electrons to pair up
Fluorine - needs

one electron to complete ‘octet’
Five covalent bonds are formed; phosphorus can make use of d orbitals to expand its ‘octet’

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PHOSPHORUS(V) FLUORIDE
P
BOND PAIRS 5
LONE PAIRS 0
BOND ANGLE...
SHAPE...
120° & 90°
TRIGONAL BIPYRAMIDAL
Phosphorus - has

five electrons to pair up
Fluorine - needs one electron to complete ‘octet’
Five covalent bonds are formed; phosphorus can make use of d orbitals to expand its ‘octet’

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SULPHUR(VI) FLUORIDE
Sulphur - has six electrons to pair up
Fluorine - needs

one electron to complete ‘octet’
Six covalent bonds are formed; sulphur can make use of d orbitals to expand its ‘octet’

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SULPHUR(VI) FLUORIDE
BOND PAIRS 6
LONE PAIRS 0
BOND ANGLE...
SHAPE...
90°
OCTAHEDRAL
Sulphur - has six electrons to

pair up
Fluorine - needs one electron to complete ‘octet’
Six covalent bonds are formed; sulphur can make use of d orbitals to expand its ‘octet’

90°

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SULPHUR(VI) FLUORIDE
BOND PAIRS 6
LONE PAIRS 0
BOND ANGLE...
SHAPE...
90°
OCTAHEDRAL
Sulphur - has six electrons to

pair up
Fluorine - needs one electron to complete ‘octet’
Six covalent bonds are formed; sulphur can make use of d orbitals to expand its ‘octet’

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IRREGULAR SHAPES
If a molecule, or ion, has lone pairs on the

central atom, the shapes are slightly distorted away from the regular shapes. This is because of the extra repulsion caused by the lone pairs.

BOND PAIR - BOND PAIR < LONE PAIR - BOND PAIR < LONE PAIR - LONE PAIR

As a result of the extra repulsion, bond angles tend to be slightly less as the bonds are squeezed together.

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AMMONIA
Nitrogen has five electrons in its outer shell
It cannot

pair up all five - it is restricted to eight electrons in its outer shell
It pairs up only three of its five electrons
3 covalent bonds are formed and a pair of non-bonded electrons is left
As the total number of electron pairs is 4, the shape is BASED on a tetrahedron

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AMMONIA
ANGLE... 107°
SHAPE... PYRAMIDAL
H
H
N
H
The shape is based on a tetrahedron but

not all the repulsions are the same
LP-BP REPULSIONS > BP-BP REPULSIONS
The N-H bonds are pushed closer together
Lone pairs are not included in the shape

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AMMONIA

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WATER
Oxygen has six electrons in its outer shell
It cannot

pair up all six - it is restricted to eight electrons in its outer shell
It pairs up only two of its six electrons
2 covalent bonds are formed and 2 pairs of non-bonded electrons are left
As the total number of electron pairs is 4, the shape is BASED on a tetrahedron

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ANGLE... 104.5°
SHAPE... ANGULAR
H
O
H
H
O
H
104.5°
H
O
H
The shape is based on a tetrahedron but not

all the repulsions are the same
LP-LP REPULSIONS > LP-BP REPULSIONS > BP-BP REPULSIONS
The O-H bonds are pushed even closer together
Lone pairs are not included in the shape

WATER

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XENON TETRAFLUORIDE
Xenon has eight electrons in its outer shell
It

pairs up four of its eight electrons
4 covalent bonds are formed and 2 pairs of non-bonded electrons are left
As the total number of electron pairs is 6, the shape is BASED on an octahedron

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XENON TETRAFLUORIDE
F
F
F
F
Xe
ANGLE... 90°
SHAPE... SQUARE PLANAR
As the total number of electron pairs

is 6, the shape is BASED on an octahedron
There are two possible spatial arrangements for the lone pairs
The preferred shape has the two lone pairs opposite each other

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CALCULATING THE SHAPE OF IONS
The shape of a complex ion is

calculated in the same way a molecule by...
calculating the number of electrons in the outer shell of the central species *
pairing up electrons, making sure the outer shell maximum is not exceeded
calculating the number of bond pairs and lone pairs
using ELECTRON PAIR REPULSION THEORY to calculate shape and bond angle(s)
the number of electrons in the outer shell depends on the charge on the ion
if the ion is positive you remove as many electrons as there are positive charges
if the ion is negative you add as many electrons as there are negative charges
e..g. for PF6- add one electron to the outer shell of P
for PCl4+ remove one electron from the outer shell of P

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SHAPES OF IONS
Draw outer shell electrons of central atom
EXAMPLE

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SHAPES OF IONS
NH4+
NH2-
Draw outer shell electrons of central atom
For every positive

charge on the ion, remove an electron from the outer shell...
For every negative charge add an electron to the outer shell...
for NH4+ remove 1 electron
for NH2- add 1 electron

EXAMPLE

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SHAPES OF IONS
NH4+
NH2-
Draw outer shell electrons of central atom
For every positive

charge on the ion, remove an electron from the outer shell
For every negative charge add an electron to the outer shell..
for NH4+ remove 1 electron
for NH2- add 1 electron
Pair up electrons in the usual way

EXAMPLE

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SHAPES OF IONS
NH4+
NH2-
BOND PAIRS 4
LONE PAIRS 0
TETRADHEDRAL
H-N-H 109.5°
BOND PAIRS 2
LONE PAIRS

2
ANGULAR
H-N-H 104.5°

Draw outer shell electrons of central atom
For every positive charge on the ion, remove an electron from the outer shell
For every negative charge add an electron to the outer shell..
for NH4+ remove 1 electron
for NH2- add 1 electron
Pair up electrons in the usual way
Work out shape and bond angle(s) from number of bond pairs and lone pairs.

EXAMPLE

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SHAPES OF IONS
BOND PAIRS 3 PYRAMIDAL
LONE PAIRS 1 H-N-H 107°
BOND PAIRS 4 TETRAHEDRAL
LONE PAIRS

0 H-N-H 109.5°

BOND PAIRS 2 ANGULAR
LONE PAIRS 2 H-N-H 104.5°

NH4+

NH2-

NH3

REVIEW

Слайд 37

MOLECULES WITH DOUBLE BONDS
C
O
O
Carbon - needs four electrons to complete its

shell
Oxygen - needs two electron to complete its shell

The atoms share two electrons
each to form two double bonds

The shape of a compound with a double bond is calculated in the same way. A double bond repels other bonds as if it was single e.g. carbon dioxide

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MOLECULES WITH DOUBLE BONDS
C
O
O
Carbon - needs four electrons to complete its

shell
Oxygen - needs two electron to complete its shell

The atoms share two electrons
each to form two double bonds

DOUBLE BOND PAIRS 2
LONE PAIRS 0

Double bonds behave exactly as single bonds for repulsion purposes so the shape will be the same as a molecule with two single bonds and no lone pairs.

The shape of a compound with a double bond is calculated in the same way. A double bond repels other bonds as if it was single e.g. carbon dioxide

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OTHER EXAMPLES
BrF5
BOND PAIRS 5
LONE PAIRS 1
‘UMBRELLA’
ANGLES 90° <90°
F
F
F
F
Br
F

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ANSWERS ON NEXT PAGE
TEST QUESTIONS
For each of the following ions/molecules, state

the number of bond pairs
state the number of lone pairs
state the bond angle(s)
state, or draw, the shape

SiCl4

PCl6-

H2S

SiCl62-

PCl4+

BF3

Слайд 41

TEST QUESTIONS
3 bp 0 lp 120º trigonal planar boron pairs up all 3 electrons in
its

outer shell
4 bp 0 lp 109.5º tetrahedral silicon pairs up all 4 electrons in
its outer shell
4 bp 0 lp 109.5º tetrahedral as ion is +, remove an electron
in the outer shell then pair up
6 bp 0 lp 90º octahedral as the ion is - , add one electron to
the 5 in the outer shell then pair up
6 bp 0 lp 90º octahedral as the ion is 2-, add two electrons
to the outer shell then pair up
2 bp 2 lp 92º angular sulphur pairs up 2 of its 6 electrons in its outer shell -
2 lone pairs are left

BF3

SiCl4

PCl6-

H2S

SiCl62-

PCl4+

ANSWER

For each of the following ions/molecules, state the number of bond pairs
state the number of lone pairs
state the bond angle(s)
state, or draw, the shape

Слайд 42

REVISION CHECK
What should you be able to do?
Recall the theory of

Electron Pair Repulsion
Understand why repulsion between electron pairs affects the shape
Recall and explain the shapes and bond angles of molecules with 2,3,4,5 and 6 bond pairs
Recall the relative strengths of bond pair and lone pair repulsions
Recall and explain the shapes and bond angles of water and ammonia
Apply the above concepts to other molecules and ions, including those with double bonds

CAN YOU DO ALL OF THESE? YES NO

Слайд 43

You need to go over the relevant topic(s) again
Click on the

button to
return to the menu

Слайд 44

Shapes of molecules

Содержание

INTRODUCTIONThis Powerpoint show is one of several produced to help students

CONTENTS Prior knowledge Electron pair repulsion theory The regular molecular

Before you start it would be helpful to… know the definition

ELECTRON PAIR REPULSION THEORY“THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR

ELECTRON PAIR REPULSION THEORY“THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR

REGULAR SHAPESMolecules, or ions, possessing ONLY BOND PAIRS of electrons fit

BERYLLIUM CHLORIDEBeryllium - has two electrons to pair upChlorine - needs

BERYLLIUM CHLORIDEBOND PAIRS 2LONE PAIRS 0BOND ANGLE...SHAPE...180°LINEARBeryllium - has two electrons to pair

ADDING ANOTHER ATOM - ANIMATION

AlALUMINIUM CHLORIDEAluminium - has three electrons to pair upChlorine - needs

AlALUMINIUM CHLORIDEClClAl120°ClBOND PAIRS 3LONE PAIRS 0BOND ANGLE...SHAPE...120°TRIGONAL PLANARAluminium - has three electrons to

AlALUMINIUM CHLORIDEClClAl120°ClBOND PAIRS 3LONE PAIRS 0BOND ANGLE...SHAPE...120°TRIGONAL PLANARAluminium - has three electrons to

ADDING ANOTHER ATOM - ANIMATION

METHANECarbon - has four electrons to pair upHydrogen - 1 electron

METHANEBOND PAIRS 4LONE PAIRS 0BOND ANGLE...SHAPE...109.5°TETRAHEDRALCarbon - has four electrons to pair upHydrogen

METHANEBOND PAIRS 4LONE PAIRS 0BOND ANGLE...SHAPE...109.5°TETRAHEDRALCarbon - has four electrons to pair upHydrogen

PHOSPHORUS(V) FLUORIDEPPhosphorus - has five electrons to pair upFluorine - needs

PHOSPHORUS(V) FLUORIDEPBOND PAIRS 5LONE PAIRS 0BOND ANGLE...SHAPE...120° & 90° TRIGONAL BIPYRAMIDALPhosphorus - has

SULPHUR(VI) FLUORIDESulphur - has six electrons to pair upFluorine - needs

SULPHUR(VI) FLUORIDEBOND PAIRS 6LONE PAIRS 0BOND ANGLE...SHAPE...90° OCTAHEDRALSulphur - has six electrons to

SULPHUR(VI) FLUORIDEBOND PAIRS 6LONE PAIRS 0BOND ANGLE...SHAPE...90° OCTAHEDRALSulphur - has six electrons to

IRREGULAR SHAPESIf a molecule, or ion, has lone pairs on the

AMMONIA Nitrogen has five electrons in its outer shell It cannot

AMMONIAANGLE... 107°SHAPE... PYRAMIDALHHNH The shape is based on a tetrahedron but

AMMONIA

WATER Oxygen has six electrons in its outer shell It cannot

ANGLE... 104.5°SHAPE... ANGULARHOHHOH104.5°HOH The shape is based on a tetrahedron but not

XENON TETRAFLUORIDE Xenon has eight electrons in its outer shell It

XENON TETRAFLUORIDEFFFFXeANGLE... 90°SHAPE... SQUARE PLANAR As the total number of electron pairs

CALCULATING THE SHAPE OF IONSThe shape of a complex ion is

SHAPES OF IONSDraw outer shell electrons of central atomEXAMPLE

SHAPES OF IONSNH4+NH2-Draw outer shell electrons of central atomFor every positive

SHAPES OF IONSNH4+NH2-Draw outer shell electrons of central atomFor every positive

SHAPES OF IONSNH4+NH2-BOND PAIRS 4LONE PAIRS 0TETRADHEDRALH-N-H 109.5°BOND PAIRS 2LONE PAIRS

SHAPES OF IONSBOND PAIRS 3 PYRAMIDALLONE PAIRS 1 H-N-H 107°BOND PAIRS 4 TETRAHEDRALLONE PAIRS

MOLECULES WITH DOUBLE BONDSCOOCarbon - needs four electrons to complete its

MOLECULES WITH DOUBLE BONDSCOOCarbon - needs four electrons to complete its

OTHER EXAMPLESBrF5BOND PAIRS 5LONE PAIRS 1‘UMBRELLA’ANGLES 90° <90° FFFFBrF

ANSWERS ON NEXT PAGETEST QUESTIONSFor each of the following ions/molecules, state

TEST QUESTIONS3 bp 0 lp 120º trigonal planar boron pairs up all 3 electrons in its

REVISION CHECKWhat should you be able to do?Recall the theory of

You need to go over the relevant topic(s) againClick on the

WELL DONE!Try some past paper questions

Похожие презентации

INTRODUCTION
This Powerpoint show is one of several produced to help students

CONTENTS
Prior knowledge
Electron pair repulsion theory
The regular molecular

Before you start it would be helpful to…
know the definition

ELECTRON PAIR REPULSION THEORY
“THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR

ELECTRON PAIR REPULSION THEORY
“THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR

REGULAR SHAPES
Molecules, or ions, possessing ONLY BOND PAIRS of electrons fit

BERYLLIUM CHLORIDE
Beryllium - has two electrons to pair up
Chlorine - needs

BERYLLIUM CHLORIDE
BOND PAIRS 2
LONE PAIRS 0
BOND ANGLE...
SHAPE...
180°
LINEAR
Beryllium - has two electrons to pair

Al
ALUMINIUM CHLORIDE
Aluminium - has three electrons to pair up
Chlorine - needs

Al
ALUMINIUM CHLORIDE
Cl
Cl
Al
120°
Cl
BOND PAIRS 3
LONE PAIRS 0
BOND ANGLE...
SHAPE...
120°
TRIGONAL PLANAR
Aluminium - has three electrons to

Al
ALUMINIUM CHLORIDE
Cl
Cl
Al
120°
Cl
BOND PAIRS 3
LONE PAIRS 0
BOND ANGLE...
SHAPE...
120°
TRIGONAL PLANAR
Aluminium - has three electrons to

METHANE
Carbon - has four electrons to pair up
Hydrogen - 1 electron

METHANE
BOND PAIRS 4
LONE PAIRS 0
BOND ANGLE...
SHAPE...
109.5°
TETRAHEDRAL
Carbon - has four electrons to pair up
Hydrogen

METHANE
BOND PAIRS 4
LONE PAIRS 0
BOND ANGLE...
SHAPE...
109.5°
TETRAHEDRAL
Carbon - has four electrons to pair up
Hydrogen

PHOSPHORUS(V) FLUORIDE
P
Phosphorus - has five electrons to pair up
Fluorine - needs

PHOSPHORUS(V) FLUORIDE
P
BOND PAIRS 5
LONE PAIRS 0
BOND ANGLE...
SHAPE...
120° & 90°
TRIGONAL BIPYRAMIDAL
Phosphorus - has

SULPHUR(VI) FLUORIDE
Sulphur - has six electrons to pair up
Fluorine - needs

SULPHUR(VI) FLUORIDE
BOND PAIRS 6
LONE PAIRS 0
BOND ANGLE...
SHAPE...
90°
OCTAHEDRAL
Sulphur - has six electrons to

SULPHUR(VI) FLUORIDE
BOND PAIRS 6
LONE PAIRS 0
BOND ANGLE...
SHAPE...
90°
OCTAHEDRAL
Sulphur - has six electrons to

IRREGULAR SHAPES
If a molecule, or ion, has lone pairs on the

AMMONIA
Nitrogen has five electrons in its outer shell
It cannot

AMMONIA
ANGLE... 107°
SHAPE... PYRAMIDAL
H
H
N
H
The shape is based on a tetrahedron but

WATER
Oxygen has six electrons in its outer shell
It cannot

ANGLE... 104.5°
SHAPE... ANGULAR
H
O
H
H
O
H
104.5°
H
O
H
The shape is based on a tetrahedron but not

XENON TETRAFLUORIDE
Xenon has eight electrons in its outer shell
It

XENON TETRAFLUORIDE
F
F
F
F
Xe
ANGLE... 90°
SHAPE... SQUARE PLANAR
As the total number of electron pairs

CALCULATING THE SHAPE OF IONS
The shape of a complex ion is

SHAPES OF IONS
Draw outer shell electrons of central atom
EXAMPLE

SHAPES OF IONS
NH4+
NH2-
Draw outer shell electrons of central atom
For every positive

SHAPES OF IONS
NH4+
NH2-
Draw outer shell electrons of central atom
For every positive

SHAPES OF IONS
NH4+
NH2-
BOND PAIRS 4
LONE PAIRS 0
TETRADHEDRAL
H-N-H 109.5°
BOND PAIRS 2
LONE PAIRS

SHAPES OF IONS
BOND PAIRS 3 PYRAMIDAL
LONE PAIRS 1 H-N-H 107°
BOND PAIRS 4 TETRAHEDRAL
LONE PAIRS

MOLECULES WITH DOUBLE BONDS
C
O
O
Carbon - needs four electrons to complete its

MOLECULES WITH DOUBLE BONDS
C
O
O
Carbon - needs four electrons to complete its

OTHER EXAMPLES
BrF5
BOND PAIRS 5
LONE PAIRS 1
‘UMBRELLA’
ANGLES 90° <90°
F
F
F
F
Br
F

ANSWERS ON NEXT PAGE
TEST QUESTIONS
For each of the following ions/molecules, state

TEST QUESTIONS
3 bp 0 lp 120º trigonal planar boron pairs up all 3 electrons in
its

REVISION CHECK
What should you be able to do?
Recall the theory of

You need to go over the relevant topic(s) again
Click on the

WELL DONE!
Try some past paper questions