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CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
CONCEPT: ELECTRONIC GEOMETRY
When drawing a compound you have to take into account two different systems of geometrical shape.
• The simpler system known as electronic geometry or __________ shape treats lone pairs (nonbonding electrons)
and surrounding elements as the same.
Key: A = Central Element
X = Lone Pairs and Surrounding Elements
O C O H C N
AX2 = Linear (2 Groups)
AX3 = Trigonal Planar (3 Groups)
F
BF F
SnF F
AX4 = Tetrahedral (4 Groups)
NH
HH C
Cl
ClCl
Cl
Cl
PCl
ClCl
Cl
AX5 = Trigonal Bipyramidal (5 Groups)
Xe FF
Cl
SCl Cl
Cl Cl
AX6 = Octahedral (6 Groups)
Cl
XeH
H
H
H
!
AX
XX
!
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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PRACTICE: ELECTRONIC GEOMETRY
EXAMPLE: Draw each of the following compounds and determine their electronic geometries.
PH3 BeCl2
PRACTICE 1: Draw the following compound and determine its electronic geometry.
SBr4
PRACTICE 2: Draw the following compound and determine its electronic geometry.
IF3
PRACTICE 3: Draw the following compound and determine its electronic geometry.
H2S
PRACTICE 4: Draw the following compound and determine its electronic geometry.
PO43-
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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CONCEPT: MOLECULAR GEOMETRY
When drawing a compound you have to take into account two different systems of geometrical shape.
• With the molecular geometry you treat lone pairs (nonbonding electrons) and
surrounding elements as different.
Key: A = Central Element X = Surrounding Element E = Lone Pair
O C O H C N
3 Groups2 Groups F
BF F
SnF F
AX3 - Trigonal Planar AX2E1 - Bent, Angular or V-ShapedAX2 - Linear
4 Groups NH
HHC
Cl
ClClCl H
OH
AX4 - Tetrahedral AX2E2 - Bent, Angular or V-ShapedAX3E1 - Trigonal Pyramidal
5 Groups
Xe FF
AX5 - Trigonal Bipyramidal
ClP
ClCl
Cl Cl
F Cl F
FAX4E1 - Seesaw AX2E3 - Linear
FS FF
F
AX3E2 - T-Shaped
6 Groups ClSCl Cl
Cl ClClXe
H
H
H
HAX6 - Octahedral AX4E2 - Square Planar
F
SFF F
F
AX5E1 - Square Pyramidal
AX
XX
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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PRACTICE: MOLECULAR GEOMETRY
EXAMPLE: Draw each of the following compounds and determine their molecular geometries.
PH2 – XeCl2
PRACTICE 1: Draw the following compound and determine its molecular geometry.
OBr2
PRACTICE 2: Draw the following compound and determine its molecular geometry.
SO42-
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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CONCEPT: IDEALIZED BOND ANGLES
According to the ___________________________________________ (VSEPR) model bond and lone electron pairs will
position themselves around the central element so that they are as far apart as possible.
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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PRACTICE: IDEALIZED BOND ANGLES
EXAMPLE: Determine the bond angles of each of the following compounds.
CO2 BrF4+
PRACTICE 1: Determine the bond angle of the following compound.
AsCl5
PRACTICE 2: Determine the bond angle of the following compound.
IF3
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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CONCEPT: HYBRIDIZATION
Covalent bonds are formed when atomic orbitals on different atoms overlap and electrons are shared.
Cl Cl
H H H H
ClCl
But what happens when we need to form covalent bonds with different atomic oribitals, for example BeCl2?
Be Cl
[He]2s2 [Ne]3s23p5
2
2p 2s 2p2s
Promotion
& Hybridization2p sp 2p2s
Be
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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PRACTICE: HYBRIDIZATION
EXAMPLE: For each of the given covalent compounds draw out the Lewis Structure and answer the questions
CH2Cl2 Hybridization: XeCl5+ Hybridization:
Unhybridized Orbitals: Unhybridized Orbitals: Bonding orbitals (C – H): Bonding orbitals (Xe – Cl):
PRACTICE 1: For the given covalent compound draw out the Lewis Structure and answer the questions.
IF2– Hybridization:
Unhybridized Orbitals: Bonding orbitals (I – F):
PRACTICE 2: For the given covalent compound draw out the Lewis Structure and answer the questions.
CH3+ Hybridization:
Unhybridized Orbitals:
Bonding orbitals (C – H):
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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CONCEPT: MO THEORY In the molecular orbital theory electrons are seen as being _______________, or spread out over a molecule instead of concentrated in a covalent bond.
• A(n) _______________ orbital is the region of high electron density between nuclei where a bond forms.
• A(n) _______________ orbital is the region that has zero electron density (a node) between the nuclei where a
bond can’t form.
EXAMPLE: Use a MO diagram to write the electron configuration of each of the following:
a. C22-
b. F2+
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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PRACTICE: MO THEORY
The MO diagram can be connected to the MO bond order:
Bond Order = 12
(# of e – in bonding MO – # of e – in anti-bonding MO)
A bond order __________________________ zero means that the compound is stable and exists.
A bond order __________________________ zero means the compound is unstable and does not exist.
• In general, the _______________ the bond order, the _______________ the bond.
PRACTICE: Use a MO diagram to determine if the following compound exists or not.
a. O22-
b. B2-
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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CONCEPT: HETERONUCLEAR DIATOMIC MOLECULES Molecular Orbital Theory can also be applied to heteronuclear diatomic molecules, which are composed of two different elements covalently bonded together. The key differences it has from a homonuclear diatomic molecule include:
The _________ electronegative element determines the particular MO diagram used.
The more electronegative element will possess atomic orbitals that are ________ in energy.
The _________ energy orbital contributes more to the bonding molecular orbital, while the
__________ energy orbital contributes more to the antibonding molecular orbital.
s2s
s*2s
p2p
s2p
p*2p
s*2p
Atomic Orbitals
Atomic Orbitals
Molecular Orbitals
s2s
s*2s
p2p
s2p
p*2p
s*2p
Atomic Orbitals
Atomic Orbitals
Molecular Orbitals
2s2s
2p
2p
Hydrogen Nitrogen Oxygen Neon
2s2s
2p
2p
EXAMPLE: Using your knowledge of molecular orbital diagrams, determine the bond order of the NO– ion.
CHEMISTRY - OPENSTAX 2015E
CH.8 - ADVANCED THEORIES OF COVALENT BONDING
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