Bonding Flashcards
What is an ionic bond?
Electrons are transferred from one atom to another; resulting ions are held together by electrostatic interactions
What is a covalent bond?
Electrons are shared between atoms
What do quantum numbers describe?
The energy level, shape, orientation, and spin of an electron within an atom
What do the first three quantum numbers, n, l, ml describe?
The size, shape, number and orientation of atomic orbitals an element possesses
What does the fourth quantum number, ms describe?
Spin
Name all quantum numbers in order, what the number describes, its organizational levels, and possible values:
- n, principal quantum number, size, shell, 1 to infinity (although MCAT will only test up to 7)
- l, azimuthal quantum number, shape, subshell, 0-(n-1)
- ml, magnetic quantum number, orientation, orbital, -l-+l
- ms, spin quantum number, spin, (n/a), +/- 1/2
What happens when two atomic orbitals combine?
They form molecular orbitals
What kind of molecular orbital forms when the signs of the wave functions atomic orbitals are the same?
Bonding orbital
Is a bonding orbital more or less stable, higher or lower-energy?
Lower-energy, more stable
What kind of molecular orbital forms when the signs of the wave functions of atomic orbitals are different?
Antibonding orbital
Is an antibonding orbital more or less stable, higher or lower-energy?
Higher-energy, less stable
When a molecular orbital is formed by head-to-head or tail-to-tail overlap, what is the resulting bond?
A sigma bond; single bond
All sigma bonds are what kinds of bonds?
Single bonds
When two p-orbitals line up in a parallel fashion and their electron clouds overlap, what is the resulting bond?
A pi bond
What does a double bond consist of?
A pi bond on top of an existing sigma bond
What does a triple bond consist of?
Two pi bonds and a sigma bond
Do double and triple bonds allow free rotation of atoms around the bond axis?
No, these bonds hinder movement, and essentially lock atoms into their positions
What contributes to overall bond length?
The kind of bond, triple bonds have a shorter bond length than double bonds and double bonds have a shorter bond length than single bonds
Do shorter or longer bonds hold atoms more closely together? Which require more energy to break?
Shorter bonds hold atoms more closely together, shorter bonds require more energy to break
Are double bonds stronger than single bonds?
Yes
Are individual pi bonds stronger than single, sigma bonds?
No
Why is it possible to break only one bond in a double bond, allowing isomers to be interconverted between conformations?
This is because independent pi bonds are weaker than single, sigma bonds. In the case of a double bond, where a pi bond overlaps a single bond, breaking the double bond allows atoms to freely rotate around the bond axis, and thus be interconverted between isomer conformations.
Does it require more energy to break a pi bond in a double bond or a single bond?
It requires more energy to break a sigma, single bond than to break a pi bond.
Rank the following orbitals in order of decreasing strength.
1. Triple bonds
2. Double bonds
3. Pi bonds
4. Sigma (single bonds)
Triple bond > double bond > single (sigma) bond > pi bond
What differences would be observed in a molecule containing a double bond compared to the same molecule containing only single bonds?
The bond lengths of a molecule containing a double bond would be shorter. The molecule would also be more rigid in comparison to the same molecule containing only single bonds.
What does hybridization of orbitals do?
Hybridization is a way of making all bonds to a central atom equivalent to each other
How are hybrid orbitals formed?
By mixing different types of orbitals
What kind of geometry does carbon prefer?
Tetrahedral geometry
What kind of hybridized orbitals does tetrahedral geometry utilize?
sp^3, where one s- and three p- orbitals mix
What kind of hybridization is seen in alkenes?
sp^2
How do you determine the amount of s character a certain hybrid orbital has?
See what percentage of the hybrid orbital is an s-orbital and what other percentage is a p-orbital
For sp^3 orbitals, how much s character does the orbital have?
25% s character, 75% p character
For sp^2 orbitals, how much s character does the orbital have?
33% s character, 67% p character
For sp orbitals, how much s character does the orbital have?
50% s character, 50% p character
What kind of geometry do molecules with sp orbitals exhibit?
linear
What does conjugation of bonds refer to?
Conjugation requires alternating single and multiple bonds that allows delocalization of electrons across the entire system, improving overall molecular stability
What are resonance structures?
Resonance structures differ in their placement of electrons in hybridized p-orbitals and require bond conjugation to delocalize electrons in a molecule
How does the true electron density of a compound relate to its resonance structure?
The true electron density is a weighted average of the resonance structures of a given compound, favoring the most stable structures
What is bond strength determined by?
The degree of orbital overlap; the greater the overlap, the greater the bond strength
Why is a pi bond weaker than a single bond?
There is significantly less overlap between the unhybridized p-orbitals of a pi bond than between the s-orbitals or hybrid orbitals of a single bond
