About 1923, __ suggested that the properties of electrons in atoms are better explained by treating the electrons as __ rather than __.
Louis de Broglie
waves
particles
Two kinds of waves and examples
traveling: sound waves that carry thunderclap and water waves
Standing waves (vibrate in a fixed location): inside an organ pipe
An electron in an atomic orbital is like a __: __
stationary, bound vibration: a standing wave
The orbital (take, for ex, the 1s) can be described by its __, which is the __.
Why?
wave function
mathematical description of the shape of the wave as it vibrates
all of the wave is positive in sign for a brief instant, then negative
The electron density at any point is given by __, the square fo teh wave function at that point.
Ψ^{2}
Explain the deal with the positive and negatives.
the plus sign and the minus sign of these wave funcitons are not charges. The plus or minus sign is the instantaneous phase of the constantly changing wave function.
As an example, think of a guitar. If we put our hand on one part, on each side, there are still parts moving. We call these vibrating parts __. Why? Which orbital does this resemble?
out of phase
when one is upward, the other is downward
2p
The 2p orbital has __, separated by a __. The two lobes of the p orbital are __ with each other. Whenever the wave function has a __ on one lobe, the other has a __.
two lobes
nodal plane
out of phase
plus sign
minus sign
Atomic orbitals can combine and overlap to give more complex __. We can __ and __ their __ to give __ of new orbitals. This process is called the __. The number of new orbitals generated always __.
standing waves
add
subtract
wave functions
wave functions
linear combination of atomic orbitals
equals the number of starting orbitals
Describe interaction with different atoms and same atoms,
1) When orbitals on different atoms interact, they produce molecular orbitals (MOs) that lead to bonding (or antibonding) interactions
2) When orbitals on the same atom interact, they give hybrid atomic orbitals that define the geometry of the bonds.
The stability of a covalent bond results from a large amount of __ in the __, the space between the two nuclei.
In the __, the electrons are close to __, doing what?
electron density
bonding region
bonding region
both nuclei
lowering hte overall energy
The bonding electrons also __ of hte nuclei, so the nuclei do not do what?
mask the positive charges
repel each other as much as they would otherwise
There is always an __ for the two bonded nuclei. If they are too far apart, their attraction for the bonding electrons is __. If they are too close together, their __. The __ where attraction and repulsion are balanced, which also gives the __ (the __), is the __.
optimum distance
diminsihed
electrostatic repulsion pushes them apart
internuclear distance
minimum energy
strongest bond
bond length
What happens when wave functions...
add constructively?
add destructively?
they reinforce each other
they cancel out where they overlap
When constructive interactions occurs, what happens?
the region where they are in phase has the same sign and they result in a bonding molecular orbital (bonding MO)
When most of the electron density is centered along hte line connecting the nuclei, this type of bond is called the __.
cylindrically symmetrical bond
sigma bond
__ are the most common bonds in organic com[ounds. All __ in organic compounds are __, and every __ contains __.
sigma bonds (σ)
single bonds
sigma bonds
double or triple bond
one sigma bond
When two orbitals overlap out of phase with each other, an __ results.
For example, if the two 1s wave functions have opposite signs, they will __ where they ___, resulting in a __ (actually a __) separating the two atoms.
antibonding molecular orbital
cancel out
overlap
node
nodal plane
What does the presence of a node separating the two nuclei usually indicate?
Symbol for it?
that the orbital is nonbonding
σ* to indicate an antibonding (*), cylindrical (σ) molecular orbital
Which has more energy than its atomic orbital, bonding or antibonding?
antibonding
Both bonding and antibonding orbitals exist in all molecules, but the __ are usually __.
antibonding orbitals (such as σ*)
vacant in stable molecules
Antibonding molecular orbitals usually __.
participate in reactions
What happens when two p orbitals overlap along the line ebtween the nuclei?
a bonding orbital and an antibonding orbital result
Once again, msot of the electron density is centered along __. This __ is another type of __.
the line between the nuclei
linear overlap
sigma bonding MO
A pi bond results from what?
overlap between two p orbitals oriented perpendicular to the line connecting hte nuclei
These parallel orbitals overlap __, with most of the electron density centered __ the line connecting the nuclei. This overlap is __, not __; so, a pi molecular orbital is not __.
sideways
above and below
parallel
linear
cylindrically symmetrical
What does a double bond require?
The first pair of electrons goes into the __, forming a __. The second pair of electrons cannot go into the __ or the __. It goes into a __, with its electron density centered __ the __.
the presence of four electrons in the bonding region between the nuclei.
sigma bonding MO
strong sigma bond
same orbital or same space
pi bonding MO
above and below
sigma bond
True or False:
Overlap of s and p bonds are more common than hybrid atomic orbitals.
False
not as common
Hybrid aatomic orbitals result from what?
the mixing of orbitals on the same atom
Explain the directionality of s and p orbitals
s orbitals are nondirectional
p orbitals are oriented at ninety-degree angles to one anotehr
Bond angles in organic compounds are usually close to __.
109, 120, or 180
A common way of accounting for these bond angles is the __, which is __?
Valence electron pair reulsion theory (VSEPR theory)
electron pairs repel each other, and hte bonds nad lone pairs around a central atom generally are separated by the largest possible angles
An angle of __ is the largest possible separation for __; an angle of __ is the largest separation for three pairs; and __ is the largest for two pairs.
109
four pairs of elections
120
three pairs
180
two pairs
Although s and p orbitals have the lowest energies for isolated atoms in space, they are not the best for __. To explain the shapes of common organic molecules, we assume that the s and p orbitals __.
forming bonds
combine to form hybrid atomic orbitals that separate the electron pairs more widely in space and place more electron density in the bonding region between the nuclei
Combining a p and s orbital results in what?
an sp hbrid orbal, where the electron density is concentrated toward one side of the atom
The result of hybridization is a pair of __. These hybridized orbitals provide __ in the __ for a __ and for another __.
directional sp hybrid orbitals pointed in opposite directions
enhanced electron density
bonding region
sigma bond toward the left of the atom
sigma bond toward the right
sp hybridization results in the __.
linear bonding arrangement
To orient three bonds as far apart as possible, bond angles of __ are required.
120
When an s orbital combines with two p orbitals, the resulting __ are oriented at __ to each other. Thse orbitals are called __ because they are composed of one s and two p orbitals.
three hybrid orbitals
120 angles
sp2 hybrid
The __ is called __, in contrast to the linear geometry associated with sp tbrid orbitals. There remains an __ perpendicular to the plane of the __.
120 degree arrangement
trigonal geometry
unhybridized p orbital (pz)
three sp2 hybrid orbitals
When four bonds are oriented as far apart as possible, they form a __. This __ can be explained by combining the __. The resulting four orbitals are called __ because they are composed of one s and three p orbitals.