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1.
The table above shows the first ionization energy and atomic radius of several elements. Which of the following
best helps to explain the deviation of the first ionization energy of oxygen from the overall trend?
(A) The atomic radius of oxygen is greater than the atomic radius of fluorine.
(B) The atomic radius of oxygen is less than the atomic radius of nitrogen.
(C) There is repulsion between paired electrons in oxygen’s 2p orbitals.
(D) There is attraction between paired electrons in oxygen’s 2p orbitals.
2.
Which of the following best helps to account for the fact that the F- ion is smaller than the O2- ion?
(A) F- has a larger nuclear mass than O2- has.
(B) F- has a larger nuclear charge than O2- has.
(C) F- has more electrons than O2- has.
(D) F- is more electronegative than O2- is.
(E) F- is more polarizable than O2- is.
3.
Atoms of Mg combine with atoms of F to form a compound. Atoms of which of the following elements combine
with atoms of F in the same ratio?
(A) Li
(B) Ba
(C) Al
(D) Cl
(E) Ne
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4.
For element X represented above, which of the following is the most likely explanation for the large difference
between the second and third ionization energies?
(A) The effective nuclear charge decreases with successive ionizations.
(B) The shielding of outer electrons increases with successive ionizations.
(C)
The electron removed during the third ionization is, on average, much closer to the nucleus than the first
two electrons removed were.
(D) The ionic radius increases with successive ionizations.
5.
Account for each of the following observations in terms of atomic theory and/or quantum theory.
a. Atomic size decreases from Na to Cl in the periodic table.
b. Boron commonly forms molecules of the type BX3. These molecules have a trigonal planar structure.
c. The first ionization energy of K is less than that of Na.
d. Each element displays a unique gas-phase emission spectrum.
Part A
1 point is earned for indicating the increase in nuclear charge.
1 point is earned for attributing the size decrease to the greater attraction of the nucleus for the electrons caused by the
increase in nuclear charge.
Across the periodic table from Na to Cl, the number of electrons in the s- and p- orbitals of the valence shell increases, as
does the number of protons in the nucleus. The added electrons only partially shield the added protons, resulting in an
increased effective nuclear charge. This results in a greater attraction for the electrons, drawing them closer to the nucleus,
making the atom smaller.
0
1
The student response earns two of the following points:
1 point is earned for indicating the increase in nuclear charge.
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1 point is earned for attributing the size decrease to the greater attraction of the nucleus for the electrons caused by the
increase in nuclear charge.
Across the periodic table from Na to Cl, the number of electrons in the s- and p- orbitals of the valence shell increases, as
does the number of protons in the nucleus. The added electrons only partially shield the added protons, resulting in an
increased effective nuclear charge. This results in a greater attraction for the electrons, drawing them closer to the nucleus,
making the atom smaller.
Part B
1 point is earned for describing the valence electrons and the bonds.
1 point is earned for a correct VSEPR argument.
Boron has three valence electrons, each of which can form a single covalent bond with X. The three single covalent bonds
of the boron atom orient to minimize electron-pair interaction, resulting in bond angles of 120° and a trigonal planar
structure.
0
1
2
The student response earns two of the following points:
1 point is earned for describing the valence electrons and the bonds.
1 point is earned for a correct VSEPR argument.
Boron has three valence electrons, each of which can form a single covalent bond with X. The three single covalent bonds
of the boron atom orient to minimize electron-pair interaction, resulting in bond angles of 120° and a trigonal planar
structure.
Part C
1 point is earned for the size explanation.
1 point is earned for describing the attraction to the nucleus.
Both Na and K have an s1 valence-shell electron configuration (Na: [Ne] 3s1 ; K: [Ar] 4s1). The K atom valence electron
has a higher n quantum number, placing it farther from the nucleus than the Na atom valence electron. The greater
distance results in less attraction to the nucleus. Because its valence electron is less attracted to its nucleus, the K atom has
the lower ionization energy.
0
1
2
The student response earns two of the following points:
1 point is earned for the size explanation.
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1 point is earned for describing the attraction to the nucleus.
Both Na and K have an s1 valence-shell electron configuration (Na: [Ne] 3s1 ; K: [Ar] 4s1). The K atom valence electron
has a higher n quantum number, placing it farther from the nucleus than the Na atom valence electron. The greater
distance results in less attraction to the nucleus. Because its valence electron is less attracted to its nucleus, the K atom has
the lower ionization energy.
Part D
1 point is earned for describing the quantized energy states and emission phenomenon.
1 point is earned for describing the effect of the uniqueness of the nucleus and/or electron configuration.
Each element has a unique set of quantized energy states for its electrons (because of its unique nuclear charge and unique
electron configuration). As the electrons of the element absorb quanta of energy, they change to higher energy states (are
excited) – during de-excitation, energy is released as EM radiation as the electrons cascade to lower energy states. Each
photon of the EM radiation is associated with a specific wavelength (λ = hc/E), a flux of which produces the lines of the
emission spectrum.
0
1
2
The student response earns two of the following points:
1 point is earned for describing the quantized energy states and emission phenomenon.
1 point is earned for describing the effect of the uniqueness of the nucleus and/or electron configuration.
Each element has a unique set of quantized energy states for its electrons (because of its unique nuclear charge and unique
electron configuration). As the electrons of the element absorb quanta of energy, they change to higher energy states (are
excited) – during de-excitation, energy is released as EM radiation as the electrons cascade to lower energy states. Each
photon of the EM radiation is associated with a specific wavelength (λ = hc/E), a flux of which produces the lines of the
emission spectrum.
When free Cl(g) atoms encounter O3(g) molecules in the upper atmosphere, the following reaction mechanism is
proposed to occur.
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6.
X + O3 → XO + O2
XO + O3 → X + 2 O2
–––––––––––––––––––––
2 O3 → 3 O2
The proposed mechanism can be written in a more general form, as shown above. Species other than Cl can also
decompose O3 through the same mechanism. Which of the following chemical species is most likely to decompose
O3 in the upper atmosphere through the above mechanism?
(A) He
(B) Br
(C) N2
(D) O2
7.
Which of the following rate laws for the overall reaction corresponds to the proposed mechanism?
(A) Rate = k[O3]2
(B) Rate = k[Cl][O3]
(C) Rate = k[ClO][O3] 2
(D) Rate = k[O2]3 / [ O3 ]2
8.
Which of the following reaction energy profiles best corresponds to the proposed mechanism?
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(A)
(B)
(C)
(D)
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Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one
lettered choice that best fits each statement. A choice may be used once, more than once, or not at all in each set.
(A) Cs
(B) Ag
(C) Pb
(D) Br
(E) Se
9.
Has the highest electronegativity
(A) Cs
(B) Ag
(C) Pb
(D) Br
(E) Se
10.
Has the lowest first-ionization energy
(A) Cs
(B) Ag
(C) Pb
(D) Br
(E) Se
11.
Has the largest atomic radius
(A) Cs
(B) Ag
(C) Pb
(D) Br
(E) Se
12.
The elements in which of the following have most nearly the same atomic radius?
(A) Be, B, C, N
(B) Ne, Ar, Kr, Xe
(C) Mg, Ca, Sr, Ba
(D) C, P, Se, I
(E) Cr, Mn, Fe, Co
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13.
Based on the ionization energies of element X given in the table above, which of the following is most likely the
empirical formula of an oxide of element X?
(A) XO2
(B) X2O
(C) X2O3
(D) X2O5
14.
Silicon crystals are semiconductors. Which of the following is a correct reason for the increase in the conductivity
of Si crystals when a small fraction of Si atoms are replaced with those of a different element?
(A) P atoms introduce additional mobile negative charges.
(B) P atoms introduce additional mobile positive charges.
(C) Ge atoms have more electrons than Si atoms have.
(D) Ge atoms are much smaller than Si atoms.
15.
Second Ionization Energy
Element
The decrease in the second ionization energy of alkali metals going down the group, as shown in the table above,
can be best attributed to a decrease in the coulombic force of attraction due to
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(A) the removal of core electrons
(B) an increase in effective nuclear charge
(C) an increase in the average distance of the outermost electron from the nucleus
(D) a decrease in electron-electron repulsion within the outermost shell
16.
If
reacts with chlorine to form
, which of the following elements reacts with
compound in a one-to-one ratio, and why?
(A)
, because it is in the same group as
.
, because its mass is similar to that of
(B)
to form an ionic
.
(C)
, because its mass is similar to that of
(D)
, because it has the same number of valence electrons as
.
.
has a high boiling point. Which of the following compounds is also likely to have a high boiling point, and
17.
why?
18.
(A)
, because its elements are in the same period of the periodic table.
(B)
, because its elements are in the same group of the periodic table.
(C)
, because its elements have similar electronegativities and it is a covalent compound.
(D)
, because its elements have very different electronegativities and it is an ionic compound.
Which of the following properties generally decreases across the periodic table from sodium to chlorine?
(A) First ionization energy
(B) Atomic mass
(C) Electronegativity
(D) Maximum value of oxidation number
(E) Atomic radius
19.
Which of the following elements has the largest first ionization energy?
(A) Li
(B) Be
(C) B
(D) C
(E) N
20.
Which of the following best helps to explain why
is more reactive with water than
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is?
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(A)
is softer than
(B) The atomic mass of
(C) The
.
is less than that of
ion has weaker Coulombic attraction to an anion than the
(D) The first ionization energy of
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.
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is less than that of
.
ion has.