Chem 120A
Fall 2005
October 11, 2005
8:00 – 9:20 AM
EXAM I
Name:____________________________________________________________
Student ID No.:____________________________________________________
Note: The exam time is 1 hr 15 min; the total number of points is 100. In the case of
multiple choice questions, there is only one correct answer. You must show your
work or reasoning for partial credit. A periodic table of the elements is in the back
of the exam.
1)
________________
(15 pts)
2)
________________
(8 pts)
3)
________________
(5 pts)
4)
________________
(16 pts)
5)
________________
(10 pts)
6)
________________
(12 pts)
7)
________________
(12pts)
8)
________________
(14 pts)
9)
________________
(8 pts)
________________
(100 pts)
TOTAL
1
(1) For the 4s and 5dx2-y2 hydrogen-like atomic orbitals, sketch the following:
(a) The radial function R.
(b) The radial probability function aor2R2.
(c) Contour maps of electron density.
2
(2a) Find the possible values for the l and ml quantum numbers for a 5d electron, a
4f electron, and a 7g electron.
(2b) Find the possible values for all four quantum numbers for a 3d electron.
3
(3) Give electron configurations for the following:
(a) V
(b) Br
(c) Ru3+
(d) Hg2+
(e) Sb
4
(4) Using Slater's rules, determine Z* for:
(a) A 3p electron in P,S, Cl, and Ar. Is the calculated value of Z* consistent with
the relative sizes of these atoms?
(b) A 2p electron in O2-, F-, Na+, and Mg2+. Is the calculated value of Z* consistent
with the relative sizes of these ions?
5
(4) (cont) Using Slater's rules, determine Z* for:
(c) A 4s and a 3d electron of Cu. Which type of electron is more likely to be lost
when copper forms a positive ion?
6
(5) Select the better choice for each of the following
(a) Higher ionization energy: Ca or P
P
(b) Higher electron affinity: Cl or Zn
Cl
(c) Higher ionization energy: Si or P
P
(d) Higher electron affinity: Ne or Ar
Ne
(e) Higher ionization energy: Cu or Zn
Zn
7
(6) Why are the ionization energies of the alkali metals in the order as shown
below?
Li
Na
K
Rb
Ionization
539
514
434
418
Energy (kJ/mol)
8
(7) Three isomers having the formula N2CO are known (shown below). Draw the
most important resonance structures of these isomers and determine the formal
charges:
(a) ONCN (nitrosyl cyanide)
(b) ONNC (nitrosyl isocyanide)
(c) NOCN (isonitrosyl cyanide)
(d) Which isomer do you predict to be the most stable (lowest energy) form?
9
(8) Give Lewis dot structures, sketch, and name the shapes of the following
(consider distortions):
(b) H3PO3 (one H is bonded to P)
(a) SOF6
..
..
..
F
..
..
..
O
H
O
P
O
..
H
H
F
..
F
..
..
..
..
S
..
..
..F ..
..
..
..
O
..
F
..
..
..
..F
(c) XeF2O2
(d) POCl3
..
..
..
..
..
O
F
..
O
Cl
..
.Xe
.
P
..
..
..
..
Cl
..
..F
Seasaw shape
10
..
..
Cl
..
..
..
..
O
..
..
(8) (cont.) Give Lewis dot structures, sketch, and name the shapes of the following
(consider distortions):
(g) IO4–
..
(e) SOCl2
..
..
O
..
..
..
O
..
I
Cl
..
..
O
..
S
..
..
Cl
..
..
..
O
(j) ClO2
..
Cl
..
..
O
..
..
.
..
..
O
11
..
O
..
(9) (a) Compare the structures of the azide ion, N3–, and the ozone molecule, O3.
(b) How would you expect the structure of the ozonide ion, O3–, to differ from that
of ozone? (one or two sentences)
12