MCAT General Chemistry Questions and Correct
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Quiz: Which of the following increases with increasing atomic number within
a family on the periodic table?
A) electronegativity
B) electron affinity
C) atomic radius
D) ionization energy
Ans: C) atomic radius
Only atomic radius increases going down a column. Size of an atom is
determined not only by effective nuclear charge, but also by number of
electron shells. Moving down a column, the number of electron shells
increases. Because the additional shells require additional space, atomic radius
increases as number of electron shells increases.
Quiz: Which of the following most likely represents the correct order of
ion size from greatest to smallest?
A) O2-, F-, Na+, Mg2+
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, B) Mg2+, Na+, F-, O2-
C) Na+, Mg2+, O2-, F-
D) Mg2+, Na+, O2-, F-
Ans: A) O2-, F-, Na+, Mg2+
This is an isoelectronic series, which means that the number of electrons on
each ion is the same. In an isoelectronic series, the nuclear charge increases
with increasing atomic number and draws the electrons inward with greater
force. The ion with the fewest protons produces the weakest attractive force on
the ions, so it has the largest size. Oxygen has the smallest atomic number, so it
has the fewest protons, and therefore will have the greatest ion size.
Quiz: Which of the following best explains why sulfur can make more
bonds than oxygen?
A) sulfur is more electronegative than oxygen
B) oxygen is more electronegative than sulfur
C) sulfur has 3d orbitals not available to oxygen
D) sulfur has fewer valence electrons
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, Ans: C) sulfur has 3d orbitals not available to oxygen
Only elements in the third and higher periods of the periodic table can form
more than 4 bonds. Second period elements, including oxygen, have four
valence orbitals (one 2s and three 2p) with which to form bonds. By contrast,
third period elements like sulfur can form bonds with not only one 3s and three
3p, but also five 3d orbitals. Remember that the second quantum number can
have any integer value from 0 to n-1, so when n = 3, three subshells (s, p, and
d) are available.
Quiz: Which of the following species has an unpaired electron in its
ground-state electronic configuration?
A) Ne
B) Ca+
C) Na+
D) O2-
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, Ans: B) Ca+
Atoms and ions with electron configurations identical to those of noble gases
do not have any unpaired electrons in their ground state. Ne, Na+, and O2- all
have the same electron configuration, [Ne], and therefore have no unpaired
electrons in their ground state. Ca+, by contrast, has a ground state
configuration of [Ar]4s1, and has one unpaired electron in its 4s subshell.
Quiz: What is the electron configuration of chromium?
A) [Ar] 3d6
B) [Ar] 4s13d5
C) [Ar] 4s23d3
D) [Ar] 4s24d4
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Detailed Answers (Verified Answers) ||Already
Graded A+||Newest Version
Quiz: Which of the following increases with increasing atomic number within
a family on the periodic table?
A) electronegativity
B) electron affinity
C) atomic radius
D) ionization energy
Ans: C) atomic radius
Only atomic radius increases going down a column. Size of an atom is
determined not only by effective nuclear charge, but also by number of
electron shells. Moving down a column, the number of electron shells
increases. Because the additional shells require additional space, atomic radius
increases as number of electron shells increases.
Quiz: Which of the following most likely represents the correct order of
ion size from greatest to smallest?
A) O2-, F-, Na+, Mg2+
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, B) Mg2+, Na+, F-, O2-
C) Na+, Mg2+, O2-, F-
D) Mg2+, Na+, O2-, F-
Ans: A) O2-, F-, Na+, Mg2+
This is an isoelectronic series, which means that the number of electrons on
each ion is the same. In an isoelectronic series, the nuclear charge increases
with increasing atomic number and draws the electrons inward with greater
force. The ion with the fewest protons produces the weakest attractive force on
the ions, so it has the largest size. Oxygen has the smallest atomic number, so it
has the fewest protons, and therefore will have the greatest ion size.
Quiz: Which of the following best explains why sulfur can make more
bonds than oxygen?
A) sulfur is more electronegative than oxygen
B) oxygen is more electronegative than sulfur
C) sulfur has 3d orbitals not available to oxygen
D) sulfur has fewer valence electrons
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, Ans: C) sulfur has 3d orbitals not available to oxygen
Only elements in the third and higher periods of the periodic table can form
more than 4 bonds. Second period elements, including oxygen, have four
valence orbitals (one 2s and three 2p) with which to form bonds. By contrast,
third period elements like sulfur can form bonds with not only one 3s and three
3p, but also five 3d orbitals. Remember that the second quantum number can
have any integer value from 0 to n-1, so when n = 3, three subshells (s, p, and
d) are available.
Quiz: Which of the following species has an unpaired electron in its
ground-state electronic configuration?
A) Ne
B) Ca+
C) Na+
D) O2-
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, Ans: B) Ca+
Atoms and ions with electron configurations identical to those of noble gases
do not have any unpaired electrons in their ground state. Ne, Na+, and O2- all
have the same electron configuration, [Ne], and therefore have no unpaired
electrons in their ground state. Ca+, by contrast, has a ground state
configuration of [Ar]4s1, and has one unpaired electron in its 4s subshell.
Quiz: What is the electron configuration of chromium?
A) [Ar] 3d6
B) [Ar] 4s13d5
C) [Ar] 4s23d3
D) [Ar] 4s24d4
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