Name_______________________________________
Chem 1311
First Exam
17 September 1999
In taking this examination, you are expected to adhere to the GT academic honor code. At a
minimum this requires that you utilize only the materials supplied to you (except for a nonprogramable calculator), and that you do not give help to, or accept help from, others.
1. a) Draw structures of the following molecules/ions. Your structures should: i) depict the geometry of
the species, ii) show the location of stereochemically active lone pairs of electrons on the central atom
(i.e., electron pairs that are involved in determining the shape of the molecule), iii) indicate the correct
number of non-bonding electron pairs, if any, on all terminal atoms and, iv) show formal charges on
individual atoms consistent with the number of valence shell electrons assigned to each and consistent
with the overall charge on the species.
a) SiF5
b) HCO3
c) What set of hybrid orbitals would be used by the central atoms in species 1a and 1b? 1a _________
1b _________
d) What is the bond order of the equivalent C-O bonds in the HCO3 ion? _______
2. Give ground state electron configurations for the following species
Fe3+
P3
3. The nitrogen-nitrogen and carbon-carbon bond dissociation energies in O2N-NO2 and O2C-CO2,
respectively, are very different. Draw Lewis structures for both species using the guidelines given in
problem 1 and based upon these Lewis structures predict which has the lowest bond energy and why
(25 words or less).
What is the oxidation state of nitrogen in N2O4 _____________
4. Draw a representation of the dx2-y2 orbital of the axis system given to the right. Label
the axes and show the phases (signs) of the wave function in each portion of the
orbital.
5. Draw the combination of atomic orbitals that would result in the following molecular orbitals:
σ* derived from s
π*
6. Circle the letter corresponding to the correct response to each of the following.
Which of the following species has the lowest bond order?
a) O2
b) O21-
c) O21+
d) O22-
Which of the following species requires the least energy to remove an electron?
a) O2
b) O2+
c) O2–
d) O22-
Which of the following species does not have an ionization energy that is lower than that of the
constituent atom(s)?
a) F2
b) O2
c) O2
d) N2
The ratio of the wavelength of the n=3 to n=2 for Li2+ to that of its n=4 to n=1 transition is?
a) <1
b) 1
c) >1
d) none of these
The number of unpaired electrons in the ground state of the gaseous Co2+ ion is
a) 2
b) 3
c) 4
d) none of these
Which of the following species is least likely to exist as a stable molecule or counter ion?
a) SiF62-
b) SiF4
c) SiF5
d) SiF2
Which species has the largest radius?
a) Cl
b) Ar
c) K1+
d) all are the same
Which molecule has bonds that are the most polar?
a) ClO2
b) O3
c) OCl2
d) CO2
Which set of quantum numbers designates a p orbital?
a) n = 2, o = 2, mo = 0
c) n = 3, o = 1, mo = -2
b) n = 4, o = 2, mo = 2
d) n = 3, o = 1, mo = -1
In which of the following species would the central atom not be sp3d2 hybridized?
a) BrF5
b) XeF4
c) SF5–
d) none of these
The lowest energy electronic transition for any polyatomic species involves excitation of an electron from
the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital). For
molecular nitrogen this transition is
a) σ* S π
b) σ S π*
c) π S π*
d) π* S σ*