Orgo Chapter 3 Quiz
Within one principle energy level, which sub shell has the least energy? a. s b. p c. d f. f
(least energy) s < p < d < f (most energy)
An electron is known to be in the n = 4 shell and the l = 2 sub shell. How many possible combinations of quantum numbers could this electron have?
- Ml = -2, -1, 0, 1, 2 - in each orbital, electrons can have positive or negative spin - 5 X 2 = 10 possible combinations
How are sigma bonds formed?
- formed by head-to-head overlap of two s orbitals or hybridized orbitals - density of electrons concentrated between two nuclei of bonding atoms
Why is a pi bond weaker than a single bond?
- pi bonds have less overlap between the unhybridized p orbital due to parallel orientation than s orbitals or hybrid orbitals of sigma bond
Which of the following hybridizations does the Be in BeH2 assume? a. sp b. sp2 c. sp3 d. sp3d
A: sp - Beryllium has only two electrons in its valence shell - when it bonds to two hydrogens, it requires two hybridized orbitals (hybridization must be "sp") - only single bonds doesn't mean hybridization must be sp3 - two unhybridized orbitals around beryllium are empty in BeH2, which takes on the linear geometry of sp
A carbon atom participates in one double bond. As such, this carbon contains orbitals with: a. hybridization between the s orbital and one p orbital b. hybridization between s orbital and two p orbitals c. hybridization between s orbital and three p orbitals d. unhybridized s character
B: double bond is sp2 - one s orbital hybridizes two p orbitals to form three sp2 hybridized orbitals - third p orbital remains unhybridized and takes part in forming the pi of the double bond - there's an unhybridized p orbital, but no unhybridized s orbitals (not D!)
Pi bonds are formed by which of the following orbitals? a. two s orbitals b. two p orbitals c. one s and one p orbital d. two sp2 hybridized orbitals
B: pi bonds formed by parallel overlap of unhybridized p orbitals - electron density concentrated above and below bonding axis
Two atomic orbitals may combine to form I. a bonding molecular orbital II. an anti bonding molecular orbital III. hybridized orbital
I, II, and III - when atomic orbitals combine, they form molecular orbitals - when two atomic orbitals with same sign are added head-to-head or tail-to-tail, they form bonding molecular orbitals - when two atomic orbitals with opposite signs are added head to head or tail to tail, they form anti bonding molecular orbitals - atomic orbitals can also hybridize, forming sp3, sp2, or sp orbitals
Why is a single bond stronger than a pi bond? I. pi bonds have greater orbital overlap II. s orbitals have more overlap than p orbitals III. sp3 hybridization is always unstable
II only - bond strength determined by degree of orbital overlap: greater overlap, greater bond strength
Resonance structure describes I. hybrid of all possible structures that contribute to electron distribution II. potential arrangement of electrons in a molecule III. single form that molecule most often takes
II only - resonance structures describes an arrangement of electrons in a molecule - different resonance structures can be driven by doing electrons in unhybridized p orbitals with conjugated bonds - not I because electron density in a molecule is the weighted average of all possible resonance structures
