hybridization of atomic orbitals some material copyright pgcc chm 101 sinex some graphics from...
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Hybridization ofAtomic Orbitals
Some Material Copyright PGCC CHM 101 SinexSome Graphics from Nelson Chemistry 12
Textbook
Atomic Orbitals Don’t Work?
To explain molecular geometry:
• In methane, CH4 , the shape is tetrahedral.
• The valence electrons of carbon should be two in s, and two in p.
• The p orbitals would have to be at right angles.
• The atomic orbitals change when making a molecule
Valence Bond Theory
• Atomic orbitals overlap when a bond is formed between atoms
• A new set of orbitals is formed • Each orbital contains a pair of
electrons• These are called hybrid orbitals• How do they look? See p234 Table 1
Hybridization
• p234 Table 1Ex: sp3 hybridization
sp3 Hybridization
• The s and p orbitals blend and end up with the tetrahedral geometry.
• one s orbital combines with three p orbitals.
• sp3 hybridization has tetrahedral geometry.
2p
Hybridization sp3
2s
Energy
In Terms of Energy
Notation?
sp3
•One s orbital and three p orbitals•Each orbital holds 2 electrons
Illustrating Hybridization
Animation of hybridizationhybridization
Visualization of orbitalshybrid orbitals
Double and Triple Bonds
Ex: C2H4
• Double bond acts as one pair.• Geometry - trigonal planar• Have to end up with three blended
orbitals.• Use one s and two p orbitals to make
sp2 orbitals.• Leaves one p orbital perpendicular.
Where is the P orbital?
• Perpendicular• The overlap of orbitals (end-to-end)
makes a sigma bond ( bond)
hybrid orbitals – sp, sp2, or sp3
formation of bond
remaining p orbitals form sp or sp2
bond
The overlap of orbitals (side-to-side)
makes a pi bond ( bond)
Planar molecule (each carbon is trigonal planar) with cloud above and below the plane
bond hinders rotation about the carbon-to-carbon bond
sp Hybridization
• End up with two lobes 180º apart.• p orbitals are at right angles• Makes room for two bonds and
two bonds.• A triple bond or two double
bonds.
Bond Formation From Hybridization
• Single bond - sigma bond
• Double bond – sigma bond + pi bond
• Triple bond – sigma bond + pi bond + pi
bond How are the two pi bonds in the triple bond oriented?
end-to-end
side-to-side
How about the electron density around a C-C bond?
C2H6
C2H4C2H2
single bond double bond triple bond
Polar orNon-polar
H+
attack?
Summary