Chapter 7 Flashcards
Localized vs delocalized
localized: one random double bond
delocalized: double bond, single bond, double bond, single bond ; more than one resonance structure
Draw the MO diagram for H2
see chapter 7 notes
How do you calculate bond order?
(bonding-antibonding)/ 2
Draw the MO diagram for He2+
see chapter 7 notes
Use MO diagrams to explain the trend in the following bond energies:
B2= 290 KJ/mol
C2 = 600 KJ/mol
N2 = 942 KJ/mol
B2 bond order = 1
C2 bond order = 2
N2 bond order = 3
bond order increases as energy increases
The first ionization energy of NO is 891 KJ/mol, that of N2 is 1500 KJ/mol and that of CO is 1350 KJ/mol. Use MO electron configurations to explain why NO ionizes more easily than either N2 or CO.
NO ionizes more easily because removing an electron from an antibond makes the molecule more stable. N2 and CO would be unstabilized if an electron were to be removed.
Electrical eye door openers use photoconductors that respond to infrared light with a wavelength of 1.5 um. Which is suitable for photoconductors operating at this wavelength, germanium (Eg=64 kJ/mol) or silicon (Eg= 105 kJ/mol)
E= nhc/landa
= 80000 J/mol or 80kJ
germanium has enough energy
silicon not enough energy
For the N and B atoms in the molecule NB, determine the hybridization and the formal charge for each.
N: sp3 and +1
B: sp3 and -1
Determine the number of sigma and pi bond in each molecule.
a) H2C=CCl2
b) HOOC-COOH
c) FHC=C=CHF
a) sigma = 5 pi= 1
b) sigma = 7 pi = 2
c) sigma = 6 pi = 2
Construct the MO diagram for H2+ and then identify the bond order.
see cahier
bond order= 1/2
Which of the following contains one or more localized or delocalized pi bonds? H20 O3 HCN CO3- C2H4
delocalized: O3, CO32-
localized: HCN, C2H4
* H20 has no double bonds*
Conductor vs semiconductor vs insulator
conductor: no band gap, electrons easily promoted to conduction band to conduct electricity
semiconductor: small band gap where electrons can gain enough energy to be promoted into the conduction band to conduct electricity
insulator: does not conduct electricity due to huge band gap where too much energy is required for electrons to be promoted to the conduction band
The conductivity of intrinsic semiconductors, such as silicon and germanium, can be increased when small amounts of group 3A or group 5A elements are added, a process called dping. The resulting semiconductors are called either p-type or n-type semiconductors. Classify Ge doped with Ga and Si doped with P.
p-type: Ge doped with Ga
Ge has one more electron than Ga, making Ga more positive
n-type: Si doped with P
* Si has one less electron than P, making P more negative*
CdTe is a semiconductor material that has a band of 139 kJ/mol. What is the longest wavelength of light, in nm, that will excite an electron from the valence band to the conduction band?
E=nhc/ landa
landa= nhc/E
= 8.61*10^2 nm
For which of the following molecules and ions does the central atom nitrogen have sp3 hybridization?
a) HNO3
b) NBr3
c) NO2
d) NO
e) NOBr
b) NB3
tetrahedral