Valence Bond Theory Flashcards
What is valence bond theory?
Describes a covalent bond as resulting from the overlap of half-filled atomic orbitals, one for each atom.
Each half-filled atomic orbital contains a single what?
Electron
Two orbital can overlap when they what?
Partially occupy the same region of space.
Orbitals must be at specific distance and what?
Orientation to each other in order to overlap effectively.
More Overlap = what?
Stronger Bond
How do sigma bonds form?
End-to-end overlap along the internuclear axis.
What are the possible sigma bonds?
s-s, s-p, and p-p
How do pi bonds form?
Side-to-side overlap on the opposite side of the internuclear axis. Both p orbitals must be parallel for a pi bond to form.
All single bonds are what?
Sigma bonds
Multiple bonds (double-bonds, triple-bonds, etc.) consists of what?
One sigma bond and one or more pi bond.
What is hybridization?
Combining the wavefunctions for multiple atomic orbitals.
What is the point of hybridization?
To form new atomic orbitals that are more suitable for the atom to form bonds.
Hybridization does not exist in what?
Isolated atoms
A set of hybrid orbitals is generated by combining what?
Atomic orbitals.
All orbitals in a set of hybrid orbitals are what?
Equivalent in shape and energy
Hybrid orbitals overlap to form what?
Sigma bonds
Unhybridized orbitals overlap to form what?
Pi bonds
sp Hybridization
S orbital combines with a p orbital which is equal to 180 degrees.
Sp^2 Hybridization
This hybridization ends up as a trigonal planar.
How to find number of domains in hybridization?
Add the superscripts of the orbitals and that should equal the number of domains (sp^2) —> 1 + 2 = 3
sp^3 Hybridization
An s orbital combines with 3 p orbitals which are equal in 109.5 degrees apart.
sp^3d Hybridization
s orbital + 3 p orbitals + d orbital which equal into 90 or 120 degrees apart.
sp^3d^2 Hybridization
s orbital + 3 p orbitals + 2 d orbitals which equal to 90 degrees apart.
When is best to use hybridization?
Works well for molecules containing small central atoms.
Sigma Bonds
Made from hybrid orbitals, electron density is along internuclear axis and can rotate freely.
Pi Bonds
Made from unhybridized p orbitals, electron density is above and below the internuclear axis, restrict rotation.
