The Central Themes of VB Theory
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The Central Themes of VB Theory Themes A set of overlapping orbitals has a maximum of two electrons that must have opposite spins. The greater the orbital overlap, the stronger (more stable) the bond. The valence atomic orbitals in a molecule are different from those in isolated atoms. here is a hybridization of atomic orbitals to form molecular rbitals.
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The Central Themes of VB Theory. Themes. A set of overlapping orbitals has a maximum of two electrons that must have opposite spins. The greater the orbital overlap, the stronger (more stable) the bond. The valence atomic orbitals in a molecule are different from those in isolated atoms. - PowerPoint PPT Presentation
Transcript of The Central Themes of VB Theory
The Central Themes of VB Theory
Themes
A set of overlapping orbitals has a maximum of two electrons that must have opposite spins.
The greater the orbital overlap, the stronger (more stable) the bond.
The valence atomic orbitals in a molecule are different from those in isolated atoms.
There is a hybridization of atomic orbitals to form molecularorbitals.
Orbital overlap and spin pairing in three diatomic molecules.
Hydrogen, H2
Hydrogen fluoride, HF
Fluorine, F2
Hybrid Orbitals
The number of hybrid orbitals obtained equals the number of atomic orbitals mixed.
The type of hybrid orbitals obtained varies with the types of atomic orbitals mixed.
Key Points
sp sp2 sp3 sp3d sp3d2
Types of Hybrid Orbitals
The sp hybrid orbitals in gaseous BeCl2.
atomic orbitals
hybrid orbitals
orbital box diagrams
The sp hybrid orbitals in gaseous BeCl2.
orbital box diagrams with orbital contours
The sp2 hybrid orbitals in BF3.
The sp3 hybrid orbitals in CH4.
The sp3 hybrid orbitals in NH3.
The sp3 hybrid orbitals in H2O.
The sp3d hybrid orbitals in PCl5.
The sp3d2 hybrid orbitals in SF6.
The bonds in ethane(C2H6).
both C are sp3 hybridizeds-sp3 overlaps to bonds
sp3-sp3 overlap to form a bondrelatively even
distribution of electron density over all bonds
The and bonds in ethylene (C2H4).
The and bonds in acetylene (C2H2).
Contours and energies of the bonding and antibonding molecular orbitals (MOs) in H2.
The bonding MO is lower in energy and the antibonding MO is higher in energy than the AOs that combined to form them.
The MO diagram for H2.
En
erg
y
MO of H2
*1s
1s
AO of H
1s
AO of H
1s
H2 bond order = 1/2(2-0) = 1
Filling molecular orbitals with electrons follows the same concept as filling atomic orbitals.
MO diagram for He2+ and He2.
En
erg
y
MO of He+
*1s
1s
AO of He+
1s
MO of He2
AO of He
1s
AO of He
1s
*1s
1s
En
erg
y
He2+ bond order = 1/2 He2 bond order = 0
AO of He
1s
*2s
2s
2s2s 2s 2s
*2s
2s
Li2 bond order = 1 Be2 bond order = 0
Bonding in s-block homonuclear diatomic molecules.E
ner
gy
Li2Be2
Contours and energies of s and p MOs through combinations of 2p atomic orbitals.
Relative MO energy levels for Period 2 homonuclear diatomic molecules.
MO energy levels for O2, F2, and Ne2
MO energy levels for B2, C2, and N2
without 2s-2p mixing
with 2s-2p mixing
MO occupancy and molecular properties for B2 through Ne2
The paramagnetic properties of O2
