February Vacation Review Problem Set
1. Complete the following table
Symbol
Number of
protons in
nucleus
238U
Number of
neutrons in
nucleus
20
20
35
15
44
16
Number of
electrons
Net Charge
2+
89Y
36
3-
2. The element europium exists in nature as two isotopes, 151Eu has a mass of 150.9196 amu, and 152 Eu has a mass of
152.9209 amu. The average atomic mass of europium is 151.96 amu. Calculate the relative abundance of the europium
isotopes and draw the expected PES spectrum.
3. The elements Si Ga, As, Ge, Al, Cd, S and Se are all used in the manufacture of various semiconductor devices. Write the
expected electron configuration for these atoms.
4. Arrange the following groups of atoms in order of increasing atomic radii (size)
a. Te, S, Se
b. K, Br, Ni
c. Ba, Si, F
5. In each of the following sets, which atom or ion has the smallest radius: explain why?
a. H, He
b. Cl, In, Se
c. element 120, element 119, element 116
d. Nb, Zn, Si
e. Na-, Na, Na+
1
6. In each of the following sets, which atom or ion has the smallest ionization energy? Explain why?
a. Ca, Sr, Ba
b. K, Mn, Ga
c. N, O, F
d S2-, S, S2+
e. Cs, Ge, Ar
Mg and K
F and Cl
7. For each of the pairs of elements above pick the atom with
a. More favorable electron affinity
b. Higher ionization energy
c. Larger size
8. Describe the Bohr model of the atom and the quantum model. Contrast what is similar and what is different between both
of the models.
9. Predict which bond in each of the following groups will be the most polar by using their position on the periodic table
a. C-FF, Si-FF, Ge-F
b. P-Cl or S-Cl
c. S-F, S-Cl, S-Br
d. Ti-Cl, Si-Cl, Ge-Cl
10. Indicate the bond polarity (Show the partial positive and partial negative ends) in the following bonds.
a. C-O
d. Br-Te
b. P-H
e. Se-S
c. H-Cl
11. Write electron configurations for the most stable ion formed by each of the following elements Te, Cl, Sr, and Li
2
12. Write Lewis structures for the following. Show all resonance structures where applicable.
a. NO2-, NO3-, N2O4 (N2O4 exists as O2N-NO2)
b. OCN-, SCN-, N3- Carbon is the central atom in OCN- and SCN-)
13. Explain the following using the curve below:
a. Completely explain the trend in boiling points for each curve.
b. Explain the different pattern in the bottom curve compared to the others.
c. Explain the different boiling points for H2O, HF, NH3
13. Fill out the attached table.
3
Molecular
formula
Lewis structure
Electrongroup
geometry
Bond
angle
Molecular
geometry
Polar or
nonpolar
Predominant
Intermolecular force
nonpolar
London dispersion forces
Example molecule: CH4
H
CH4
H
C
H
tetrahedra
l
109°
tetrahedral
H
CO2
BF3
4
CCl4
NH3
H2O
SCl2
5
I3-
SO2
CH2Cl2
PF5
6
H3O+
7