Shape of Molecule
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Transcript of Shape of Molecule
SHAPES OF MOLECULESSHAPES OF MOLECULES
COVALENT BONDCOVALENT BOND
ByBy
RIMKHONG GROUPRIMKHONG GROUP
LOOK AT THIS VDOLOOK AT THIS VDO
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 MOLECULESSHAPES OF MOLECULES
is the chemical bond that involves the sharing of pairs of electrons between atoms.
Covalent BondCovalent Bond
ELECTRON PAIR REPULSION THEORYELECTRON PAIR REPULSION THEORY
“THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR ION IS THAT WHICH KEEPS REPULSIVE FORCES TO A MINIMUM”
AlBonds are further apart so repulsive forces are less
Bonds are closer together so repulsive forces are greater
Al
All bonds are equally spaced out as far apart as possible
REGULAR SHAPESREGULAR 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
C
A covalent bond will repel another covalent bond
examples...
REGULAR SHAPESREGULAR SHAPES
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 BONDPAIRS SHAPE ANGLE(S) EXAMPLE
BERYLLIUM CHLORIDEBERYLLIUM CHLORIDE
Cl ClBe180°
BOND PAIRS 2
LONE PAIRS 0
BOND ANGLE...
SHAPE...
180°
LINEAR
ClBe Be ClCl
LINEARLINEAR
Al
ALUMINIUM CHLORIDEALUMINIUM CHLORIDE
Cl
Cl
Al120°
Cl
ClAl
Cl
Cl
Cl
BOND PAIRS 3
LONE PAIRS 0
BOND ANGLE...
SHAPE...
120°
TRIGONAL PLANAR
TRIGONAL PLANAR
METHANEMETHANE
BOND PAIRS 4
LONE PAIRS 0
BOND ANGLE...
SHAPE...
109.5°
TETRAHEDRAL
C H CH
H
H
H
109.5°
H H
C
H
H
TETRAHEDRAL
PHOSPHORUS(V)FLUORIDEPHOSPHORUS(V)FLUORIDE
FP
P
F
F
F
F
FBOND PAIRS 5
LONE PAIRS 0
BOND ANGLE...
SHAPE...
120° & 90°
TRIGONAL BIPYRAMIDAL
120°F
F
P
F
FF
90°
TRIGONAL
BIPYRAMIDAL
TRIGONAL
BIPYRAMIDAL
SULPHUR(VI) FLUORIDESULPHUR(VI) FLUORIDE
FS
BOND PAIRS 6
LONE PAIRS 0
BOND ANGLE...
SHAPE...
90°
OCTAHEDRAL
S
F
F
F
F
F
F
F
F F
FS
F
F
90°
OCTAHEDRAL
OCTAHEDRAL
ARE YOU OK!summaryTo predict the shape of a molecule: (1)Write down the Lewis dot structure for the molecule. (2)Count the number of bond pairs and lone pairs around the central atom. (3) Decide on the electron pair orientation based on the total number of electron pairs (4 = tetrahedral, 5 = trigonal bipyramidal). (4) Consider the placement of lone pairs and any distortions from "regular" shapes. (5) Name the shape based on the location of atoms
summary
CO2
CCl4
NCl5
HCN
BCl3
NH3
TEST QUESTIONSFor each of the following molecules state the number of bond pairs
state the shapestate the bond angle(s)
CO2
CCl4
NCl5
HCN
BCl3
NH3
Linear
BOND BONDPAIRS SHAPE ANGLE(S)
2 180º
Tetrahedral4 109.5º
Trigonal BipyramidalTrigonal Bipyramidal55 90º 120º90º 120º
Linear2 180º
Trigonal PlanarTrigonal Planar33 120º120º
Trigonal PyramidalTrigonal Pyramidal33 107º107º
TEST QUESTIONS
SHAPES OF SHAPES OF MOLECULESMOLECULES
The EndThe End