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CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
Molecular Orbital TheoryDR. MIOY T. HUYNHYALE UNIVERSITYCHEMISTRY 161
FALL 2019
www.mioy.org/chem161
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
Reviewing Models of Chemical Structures
PROS CONSLewis Structure: simple; 2-dimensional only;
good for n = 1, 2 all electrons paired;cannot predict magnetism;falters for: odd number electrons,resonance, multiple structuresmany exceptions (n ≥ 3)
VSEPR: expansion of Lewis; all electrons paired;3-dimensional; cannot predict magnetism;gives info on angles
VALENCE BOND gives geometric info; electrons localized to atoms;THEORY: relatively simple cannot predict magnetism easily
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
Reviewing Models of Chemical Structures
PROS CONSLewis Structure: simple; 2-dimensional only;
good for n = 1, 2 all electrons paired;cannot predict magnetism;falters for: odd number electrons,resonance, multiple structuresmany exceptions (n ≥ 3)
VSEPR: expansion of Lewis; all electrons paired;3-dimensional; cannot predict magnetism;gives info on angles
VALENCE BOND gives geometric info; electrons localized to atoms;THEORY: relatively simple cannot predict magnetism easily
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
MOTIVATING MOLECULAR ORBITAL (MO) THEORY
A commonality among the Lewis model, VSEPR theory, and valence bond theory is that electrons in these models are mostly paired ➞ diamagnetic.
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
MOTIVATING MOLECULAR ORBITAL (MO) THEORY
A commonality among the Lewis model, VSEPR theory, and valence bond theory is that electrons in these models are mostly paired ➞ diamagnetic.
As such, they all have some difficulty describing chemical structures with:
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
MOTIVATING MOLECULAR ORBITAL (MO) THEORY
A commonality among the Lewis model, VSEPR theory, and valence bond theory is that electrons in these models are mostly paired ➞ diamagnetic.
As such, they all have some difficulty describing chemical structures with:• Odd numbers of electrons (called “radicals”)
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
MOTIVATING MOLECULAR ORBITAL (MO) THEORY
A commonality among the Lewis model, VSEPR theory, and valence bond theory is that electrons in these models are mostly paired ➞ diamagnetic.
As such, they all have some difficulty describing chemical structures with:• Odd numbers of electrons (called “radicals”)• Unpaired electrons ➞ paramagnetic
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
MOTIVATING MOLECULAR ORBITAL (MO) THEORY
A commonality among the Lewis model, VSEPR theory, and valence bond theory is that electrons in these models are mostly paired ➞ diamagnetic.
As such, they all have some difficulty describing chemical structures with:• Odd numbers of electrons (called “radicals”)• Unpaired electrons ➞ paramagnetic
DIAMAGNETIC all electrons paired (↿⇂) PARAMAGNETIC unpaired electrons (↿ or ⇂)
microscopicphenomenon
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
MOTIVATING MOLECULAR ORBITAL (MO) THEORY
A commonality among the Lewis model, VSEPR theory, and valence bond theory is that electrons in these models are mostly paired ➞ diamagnetic.
As such, they all have some difficulty describing chemical structures with:• Odd numbers of electrons (called “radicals”)• Unpaired electrons ➞ paramagnetic
DIAMAGNETIC all electrons paired (↿⇂) ➞ not attracted to poles of magnetPARAMAGNETIC unpaired electrons (↿ or ⇂) ➞ attracted to poles of magnet
microscopicphenomenon
macroscopicphenomenon
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
MOTIVATING MOLECULAR ORBITAL (MO) THEORY
A commonality among the Lewis model, VSEPR theory, and valence bond theory is that electrons in these models are mostly paired ➞ diamagnetic.
As such, they all have some difficulty describing chemical structures with:• Odd numbers of electrons (called “radicals”)• Unpaired electrons ➞ paramagnetic
DIAMAGNETIC all electrons paired (↿⇂) ➞ not attracted to poles of magnetPARAMAGNETIC unpaired electrons (↿ or ⇂) ➞ attracted to poles of magnet
microscopicphenomenon
macroscopicphenomenon
We need a model of chemical bonding that can capture this phenomenon!
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
VALENCE BOND vs. MOLECULAR ORBITAL
Valence Bond (VB) Theory
Mixing atomic orbitals (AOs) within an atom.
Molecular Orbital (MO) Theory
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
VALENCE BOND vs. MOLECULAR ORBITAL
Valence Bond (VB) Theory
Mixing atomic orbitals (AOs) within an atom.
Molecular Orbital (MO) TheoryEN
ERG
Y
↿⇂
1s
↿⇂
2s
↿⇂ ↿ ↿
2p
C
↿⇂ ↿⇂ ↿⇂ ↿⇂
sp3
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
VALENCE BOND vs. MOLECULAR ORBITAL
Valence Bond (VB) Theory
Mixing atomic orbitals (AOs) within an atom.
Molecular Orbital (MO) Theory
Mixing atomic orbitals (AOs) betweentwo (or more) atoms.
ENER
GY
↿⇂
1s
↿⇂
2s
↿⇂ ↿ ↿
2p
C
↿⇂ ↿⇂ ↿⇂ ↿⇂
sp3
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
VALENCE BOND vs. MOLECULAR ORBITAL
Valence Bond (VB) Theory
Mixing atomic orbitals (AOs) within an atom.
Molecular Orbital (MO) Theory
Mixing atomic orbitals (AOs) betweentwo (or more) atoms.
ENER
GY
↿⇂
1s
↿⇂
2s
↿⇂ ↿ ↿
2p
C
↿⇂ ↿⇂ ↿⇂ ↿⇂
sp3
ENER
GY
↿⇂
1s
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂
1s
↿⇂
2s
↿ ↿ ↿
2p
N
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
VALENCE BOND vs. MOLECULAR ORBITAL
Valence Bond (VB) Theory
Mixing atomic orbitals (AOs) within an atom.
Molecular Orbital (MO) Theory
Mixing atomic orbitals (AOs) betweentwo (or more) atoms.
ENER
GY
↿⇂
1s
↿⇂
2s
↿⇂ ↿ ↿
2p
C
↿⇂ ↿⇂ ↿⇂ ↿⇂
sp3
ENER
GY
↿⇂
1s
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂
1s
↿⇂
2s
↿ ↿ ↿
2p
N
How do these mix?
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
VALENCE BOND vs. MOLECULAR ORBITAL
Valence Bond (VB) Theory
Mixing atomic orbitals (AOs) within an atom.
(only valence electrons comprise bond)
Molecular Orbital (MO) Theory
Mixing atomic orbitals (AOs) betweentwo (or more) atoms.
(only valence electrons comprise bond)
ENER
GY
↿⇂
1s
↿⇂
2s
↿⇂ ↿ ↿
2p
C
↿⇂ ↿⇂ ↿⇂ ↿⇂
sp3
ENER
GY
↿⇂
1s
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂
1s
↿⇂
2s
↿ ↿ ↿
2p
N
How do these mix?
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory Molecular Orbital (MO) Theory
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
N2(MO)
How do these mix?
How do these mix?
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
N2(MO)
How do these mix?
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿⇂ ↿⇂
π2p*
N2(MO)
Don’t worry about ordering of MOs here.
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿⇂ ↿⇂
π2p*
N2(MO)
fill from bottom up
Don’t worry about ordering of MOs here.
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿⇂ ↿⇂
π2p*
N2(MO)
fill from bottom up
Don’t worry about ordering of MOs here.
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿⇂ ↿⇂
π2p*
N2(MO)
bonding orbitals
Don’t worry about ordering of MOs here.
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿⇂ ↿⇂
π2p*
N2(MO)
bonding orbitals
antibonding orbitals
Don’t worry about ordering of MOs here.
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) TheoryBO = ½ [bonding e– – antibonding e–]
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿⇂ ↿⇂
π2p*
N2(MO)
bonding orbitals
antibonding orbitals
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) TheoryBO = ½ [8 e– – 2 e–] = 3 (triple bond)
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿⇂ ↿⇂
π2p*
N2(MO)
bonding orbitals
antibonding orbitals
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF N2 (N = 1s22s22p3)
Valence Bond (VB) Theory
Each N atom is sp-hybridized (SN = 2).The second N’s electrons are in purple.
Molecular Orbital (MO) TheoryBO = ½ [8 e– – 2 e–] = 3 (triple bond)
ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N
↿⇂ ↿⇂
sp
↿⇂ ↿⇂
p
1 lone pair1 σ bond
2 π bonds ENER
GY
↿⇂
2s
↿ ↿ ↿
2p
N(AO)
↿⇂
2s
⇂ ⇂ ⇂
2p
N(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿⇂ ↿⇂
π2p*
N2(MO)
bonding orbitals
antibonding orbitals
DIAMAGNETIC
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF O2 (O = 1s22s22p4)
Valence Bond (VB) Theory Molecular Orbital (MO) Theory
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF O2 (O = 1s22s22p4)
Valence Bond (VB) Theory
Each O atom is sp2-hybridized (SN = 3).
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O
↿⇂ ↿⇂ ↿⇂
sp2
↿⇂
p
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF O2 (O = 1s22s22p4)
Valence Bond (VB) Theory
Each O atom is sp2-hybridized (SN = 3).The second O’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O
↿⇂ ↿⇂ ↿⇂
sp2
↿⇂
p
2 lone pairs1 σ bond
1 π bond
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF O2 (O = 1s22s22p4)
Valence Bond (VB) Theory
Each O atom is sp2-hybridized (SN = 3).The second O’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O
↿⇂ ↿⇂ ↿⇂
sp2
↿⇂
p
2 lone pairs1 σ bond
1 π bond ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O(AO)
↿⇂
2s
↿⇂ ⇂ ⇂
2p
O(AO)
σ2s
σ2s
*
↿⇂
σ2p
σ2p
*
π2p
π2p*
O2(MO)
bonding orbitals
antibonding orbitals
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF O2 (O = 1s22s22p4)
Valence Bond (VB) Theory
Each O atom is sp2-hybridized (SN = 3).The second O’s electrons are in purple.
Molecular Orbital (MO) Theory
ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O
↿⇂ ↿⇂ ↿⇂
sp2
↿⇂
p
2 lone pairs1 σ bond
1 π bond ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O(AO)
↿⇂
2s
↿⇂ ⇂ ⇂
2p
O(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿↿⇂ ↿
π2p*
O2(MO)
bonding orbitals
antibonding orbitals
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF O2 (O = 1s22s22p4)
Valence Bond (VB) Theory
Each O atom is sp2-hybridized (SN = 3).The second O’s electrons are in purple.
Molecular Orbital (MO) TheoryBO = ½ [8 e– – 4 e–] = 3 (double bond)
ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O
↿⇂ ↿⇂ ↿⇂
sp2
↿⇂
p
2 lone pairs1 σ bond
1 π bond ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O(AO)
↿⇂
2s
↿⇂ ⇂ ⇂
2p
O(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿↿⇂ ↿
π2p*
O2(MO)
bonding orbitals
antibonding orbitals
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF O2 (O = 1s22s22p4)
Valence Bond (VB) Theory
Each O atom is sp2-hybridized (SN = 3).The second O’s electrons are in purple.
Molecular Orbital (MO) TheoryBO = ½ [8 e– – 4 e–] = 3 (double bond)
ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O
↿⇂ ↿⇂ ↿⇂
sp2
↿⇂
p
2 lone pairs1 σ bond
1 π bond ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O(AO)
↿⇂
2s
↿⇂ ⇂ ⇂
2p
O(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿↿⇂ ↿
π2p*
O2(MO)
bonding orbitals
antibonding orbitals
UNPAIREDELECTRONS
CHEMISTRY 161 – FALL 2019 Dr. Mioy T. Huynh
THE CASE OF O2 (O = 1s22s22p4)
Valence Bond (VB) Theory
Each O atom is sp2-hybridized (SN = 3).The second O’s electrons are in purple.
Molecular Orbital (MO) TheoryBO = ½ [8 e– – 4 e–] = 2 (double bond)
ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O
↿⇂ ↿⇂ ↿⇂
sp2
↿⇂
p
2 lone pairs1 σ bond
1 π bond ENER
GY
↿⇂
2s
↿⇂ ↿ ↿
2p
O(AO)
↿⇂
2s
↿⇂ ⇂ ⇂
2p
O(AO)
↿⇂
σ2s
↿⇂
σ2s
*
↿⇂
σ2p
↿⇂
σ2p
*
↿⇂ ↿⇂
π2p
↿↿⇂ ↿
π2p*
O2(MO)
bonding orbitals
antibonding orbitals
PARAMAGNETIC
UNPAIREDELECTRONS