The Shape of Covalent Molecules
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The Shape of Covalent Molecules 1. VSEPR Theory 2. Different ways to draw covalent bond 3. Different shapes of molecules 4. Shapes of molecules with lone pair of electrons in the central atom 5. Predict the Shapes of molecules without multiple bonds
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The Shape of Covalent Molecules. 1.VSEPR Theory 2.Different ways to draw covalent bond 3.Different shapes of molecules 4.Shapes of molecules with lone pair of electrons in the central atom 5.Predict the Shapes of molecules without multiple bonds - PowerPoint PPT Presentation
Transcript of The Shape of Covalent Molecules
The Shape of Covalent Molecules
1. VSEPR Theory
2. Different ways to draw covalent bond
3. Different shapes of molecules
4. Shapes of molecules with lone pair of electrons in the central atom
5. Predict the Shapes of molecules without multiple bonds
6. Shapes of Molecules with Multiple Bonds
VSEPR Theory
Q. What is the charge of an electron carries?
A. -ve
Q. What will happen if two bond pairs of electrons are placed around a central atom?
A. They will stay as far apart as possible to minimize the electronic repulsion.
• This is the key concept of VSEPR Theory.• If you know the no. of electron pairs around the central
atom, you can predict the shape of the molecule.
Different ways to draw covalent bond
Bond pair pointing into the paper
Bond pair on paper
Bond pair pointing out the paper
Lone pair
:
Different shapes of molecules
• If there are 2 electron pairs, the shape of the molecule is ________
Q. What is the bond angle?
A. 180
linear.
• If there are 3 electron pairs, the shape of the molecule is ____________
Q. What is the bond angle?
A. 120
trigonal planar
• If there are 4 electron pairs, the shape of the molecule is ____________
Q. What is the bond angle?
A. 109.5
tetrahedral
• If there are 5 electron pairs, the shape of the molecule is ___________________
Q. What is the axial bond angle?
A. 90
axial
equatorial
Q. What is the equatorial bond angle?
A. 120
trigonal bipyramidal
• If there are 6 electron pairs, the shape of the molecule is ____________
Q. What is the axial bond angle?
A. 90
equatorial
Q. What is the equatorial bond angle?
A. 90
axial
octahedral.
Shapes of molecules with lone pair of electrons in the central atom
In order to predict the shape of a molecule, wecan regard lone pair of electrons the same as bondpair of electrons.
The only difference is that lone pair of electronsproduces a stronger repulsion.
Remember :
l.p. l.p.repulsion
> l.p. b.p.repulsion
> b.p. b.p.repulsion
Change of molecular shape
• 3 valence pairs of electrons no lone pair 1 lone pair
..
V-shapedTrigonal planar
no lone pair
4 valence pairs of electrons
1 lone pair
..
2 lone pair
..
:
Tetrahedral Trigonal pyramidal V-shaped
no lone pair
5 valence pairs of electrons
1 lone pair
2 lone pair
Trigonal bipyramidal
Unsymmetricaltetrahedral
T-shaped
: :
:
3 lone pair
Linear
:
::
no lone pair
6 valence pairs of electrons
1 lone pair 2 lone pair
Octahedral Squarepyramidal
Squareplanar
.. ..
..
Predict the Shapes of molecules without multiple bonds
1. Count the no. of outermost e- in the central atom.
2. Add one if the particle has one negative charge or subtract one if it has one positive charge.
3. Add one for each bonding atom.
4. no. of pairs of e- = total / 2
5. no. of lone pair = no. of pairs of e- - no. of bonded atoms
e.g. 1, PCl4+
1. Count the no. of outermost e- in the central atom.
5 ( P is group 5)
2. Add one if the particle has one negative charge or subtract one if it has one positive charge.
5 - 1 = 4 (the particle has 1 +ve charge)
3. Add one for each bonding atom.
4 + 4 = 8 (there are 4 Cl atoms)
4. no. of pairs of e- = total / 2
8 / 2 = 4
5. no. of lone pair = no. of pairs of e- - no. of bonded atoms
4 - 4 = 0 tetrahedral
P
Cl
Cl
Cl
Cl+
e.g. 2, XeF2
1. Count the no. of outermost e- in the central atom.
8 ( Xe is group 0)
2. Add one if the particle has one negative charge or subtract one if it has one positive charge.
8 (the particle does not have charge)
3. Add one for each bonding atom.
8 + 2 = 10 (there are 2 F atoms)
4. no. of pairs of e- = total / 2
10 / 2 = 5
5. no. of lone pair = no. of pairs of e- - no. of bonded atoms
5 - 2 = 3 linear
Xe
F
F
::
:
Shapes of Molecules with multiple bonds
Both e- pairs must stay together in a double bond or triple bond.
We can treat them as single bonds.
• e.g. CO2
• There are 2 double bonds and no lone pair. linear
O C O
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