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College Chemistry - Problem Drill 14: The Periodic Table and Chemical Periodicity
Question No. 1 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
1. Atomic radius, a size of an atom, is defined as the distance of a nucleus to its
outermost shell of electron(s) and can be measured by half of the distance between
the nuclei of two bonded atoms. Atomic radii vary in a predictable manner across
the periodic table. Why do the atomic radii decrease along each period (row) of the
table (left to right)?
Question
(A) The greater numbers of protons and electrons increase the attraction
between the nucleus and electrons, which pulls them together closer.
(B) The electrons move faster.
(C) Neutrons have a greater affinity to the outer electrons going from left to
right.
(D) The electrons travel slower.
A. Correct!
The attraction between the center nucleus with more positive protons and outer
shells with more negative electrons increases from left to right along the period.
B. Incorrect.
The speed of the travelling electrons is not of the concern in chemistry. With more
protons and electrons, their opposite attraction grows stronger across the periodic
table.
C. Incorrect.
Feedback
The effect of neutrons typically is not being considered except in the case of
isotope. The focus is on the attraction force between positively charged nucleus and
negatively charged electrons. It increases going from left to right.
D. Incorrect.
The speed of the travelling electrons is not of the concern in chemistry. With more
protons and electrons, their opposite attraction grows stronger across the periodic
table.
Atomic radii decrease from left to right within a given period owing to the
increasing attraction (shorter distance) of more protons and electrons.
The correct answer is (A).
Solution
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Question No. 2 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
2. Electronegativity is one of the most important concepts in chemistry, specifically
in the description of bonding. It is defined as the tendency of an atom to attract (or
pull) electrons to itself. The higher the electronegativity of an atom, the greater its
attraction for bonding electrons. Explain why the electrongativity decreases going
down a group.
Question
(A) The atomic mass increases and the ability to attract electrons decreases.
(B) This is due to the farther distance of outer electrons from the nucleus, which
results in a less attraction (pull).
(C) The number of valence electrons decreases so as the ability to pull more
electrons from outside.
(D) The atomic radii decrease and the repulsion increases.
A. Incorrect.
In terms of electrostatic force (Coubomb’s Law) between a positive charge and
negative charge, the masses have nothing to do with the attraction. It is the
distance between the two charges which is inversely proportional to the force.
B. Correct.
The attraction between the nucleus and outer electrons is inversely proportional to
the distance between them. Going down a group, the distances increase and the
attractions decrease. Therefore the electronegativity decreases.
Feedback
C. Incorrect.
There is no given on the number of valence electrons. Within the same group, each
atom has the same number of outer valence electrons. This is not the reason.
D. Incorrect.
Quite the opposite, the atomic radii increase going down a group, therefore their
attractions decrease.
As the outer electrons (those involved in bonding) are farther from the nucleus,
they will feel the “pull” of the nucleus less.
The correct answer is (B).
Solution
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Question No. 3 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
3. Ionization energy (or ionization potential) is defined as the energy needed to
remove the most loosely bound electron to form an ion with a +1 charge. Explain
why ionization energy increases across a period.
Question
(A) As an atom gets heavier from left to right, it is harder to remove an electron
from it.
(B) As atomic radii increase, so as the energy needed to remove electrons.
(C) There are more valence electrons in the outer shell and it will take more
energy to remove any one of them.
(D) The radii decrease and the attractions to the electrons increase.
A. Incorrect.
Ionization energy is not about the mass of an atom, rather the energy required to
remove electrons. Think charges and the distance between them.
B. Incorrect.
Atom radii actually decrease across a period, not increase.
C. Incorrect.
Feedback
It is true that the number of valence electrons increases across the period, but that
is not the reason for the ionization energy trend.
D. Correct!
Going from left to right, the atomic radii decrease as more protons pull on more
electrons. This will make it harder to remove electrons away. Hence the ionization
energy gets higher.
Across the period to the right, the radius of the atom decreases as more protons
pull on more electrons. When an atom is smaller, the electrons are closer to the
nucleus, and therefore feel the pull more strongly. It is harder to pull electrons
away from these smaller atoms.
The correct answer is (D).
Solution
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Question No. 4 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
4. Electron affinity is defined as the energy released when an electron is added to
an atom to form an ion with a -1 charge. It reflects the ability of an atom to accept
an electron. This property has a predictable trend across the periodic table. Explain
why electron affinity decreases down a group.
Question
(A) The greater the mass, the less the energy released.
(B) As a radius increases with weaker attraction, the less energy released.
(C) The more overall electrons, the less the energy released.
(D) The smaller radii result in less in electron affinity.
A. Incorrect.
The mass has little to do with the electronic properties. Think about the distance
and attraction.
B. Correct.
Good job! This explains it. The more attraction, the more released energy. Since
the radius is getting larger (more distance), the attraction between the nucleus and
electron decreases with less energy released. The electron affinity will go down
from top-down of a group.
Feedback
C. Incorrect.
This is not the reason for the electron affinity trend. Think of the distance and the
attraction to electrons.
D. Incorrect.
The radii actually increase going down a group, not decrease.
The electron affinity is a measure of the attraction between the incoming electron
and the nucleus. The stronger the attraction, the more energy is released. Going
down a group, the radius increases and the attraction decreases. Therefore, the
electron affinity decreases.
The correct answer is (B).
Solution
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Question No. 5 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
5. A metalloid is a chemical element with properties that are in-between metals and
nonmetals. These elements touch the stair-step in the periodic table. Which set of
elements contains a metalloid?
Question
(A) Ne, Al, Li, W
(B) Fe, Ba, Cu, Zn
(C) Ar, Li, Mg, Ca
(D) K, Mn, Xe, As
A. Incorrect.
None of these elements is metalloid (B, Si, Ge, As, Sb, Te or At).
B. Incorrect.
None of these elements is metalloid (B, Si, Ge, As, Sb, Te or At).
C. Incorrect.
Feedback
None of these elements is metalloid (B, Si, Ge, As, Sb, Te or At).
D. Correct.
Among these four elements, As is the metalloid.
Look through the periodic table and note the location of the stair-step. The
metalloids touch the stair-step. You will need your color-coded periodic table of
elements (refer to the tutorial).
The correct answer is (D).
Solution
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Question No. 6 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
6. The atomic radius of an element is a measure of the size of its atoms and a
distance from its nucleus to the boundary of the surrounding electron cloud. Atomic
radii vary in a predictable manner. Which element has the largest size?
Question
(A) Na
(B) P
(C) Cl
(D) H
A. Correct.
Radius decreases from left to right across the periodic table and increases down the
periodic table. Sodium has the largest size.
B. Incorrect.
Radius decreases from left to right across the periodic table and increases down the
periodic table.
C. Incorrect.
Feedback
Radius decreases from left to right across the periodic table and increases down the
periodic table.
D. Incorrect.
Radius decreases from left to right across the periodic table and increases down the
periodic table.
Radius decreases from left to right across the periodic table and increases down the
periodic table. Therefore the far left has the largest size in a period.
The correct answer is (A).
Solution
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Question No. 7 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
7. Electronegativity is the measure of the “pull” ability of an atom to attract
electrons toward it. An atom of which element below has the greatest ability to
“pull” electrons?
Question
(A) N
(B) P
(C) As
(D) Sb
A. Correct.
The electronegativity is a measure of the ability to pull electrons to itself.
Electronegativity decreases down a group. N is on the top of this group.
B. Incorrect.
The electronegativity is a measure of the ability to pull electrons to itself.
Electronegativity decreases down a group. P is not on the top of this group.
C. Incorrect.
Feedback
The electronegativity is a measure of the ability to pull electrons to itself.
Electronegativity decreases down a group. As is not on the top of this group.
D. Incorrect.
The electronegativity is a measure of the ability to pull electrons to itself.
Electronegativity decreases down a group. Sb is not on the top of this group.
Electronegativity is the “pull” an atom has on electrons it shares in a bond with
another atom. Electronegativity decreases down a group. Nitrogen is on the top of
this group.
The correct answer is (A).
Solution
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Question No. 8 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
8. Ionization energy is the energy required to remove one electron from the parent
atom. Their values vary across the table. Which of the following has the least ability
to remove the outermost electron?
Question
(A) Br
(B) As
(C) K
(D) Ca
A. Incorrect.
Ionization energy is the measure of the energy needed to remove the outermost
electron. Ionization energy increases from left to right across the periodic table.
Look for the first element on the left.
B. Incorrect.
Ionization energy is the measure of the energy needed to remove the outermost
electron. Ionization energy increases from left to right across the periodic table.
Look for the first element on the left.
C. Correct.
Feedback
Ionization energy is the measure of the energy needed to remove the outermost
electron. Ionization energy increases from left to right across the periodic table.
Potassium is the first element in Period 4.
D. Incorrect.
Ionization energy is the measure of the energy needed to remove the outermost
electron. Ionization energy increases from left to right across the periodic table.
Look for the first element on the left.
Ionization energy is the energy required to remove an electron from an atom or
ion. The higher the ionization energy, the more difficult it is to remove an electron.
Hence, this property is indicative of reactivity.
Ionization energy increases from left to right across the periodic table. Potassium is
on the far left of this period.
The correct answer is (C).
Solution
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Question No. 9 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
9. Electron affinity is essentially the opposite of the ionization energy. It is a
measure of the amount of energy released when an electron is added to a neutral
atom or molecule. Which of the following has the highest electron affinity?
Question
(A) Ca
(B) Mg
(C) Sr
(D) Ba
A. Incorrect.
Electron affinity decreases down a group. Calcium is not on the top among these
five elements in Group 2A.
B. Correct.
Electron affinity decreases down a group. Magnesium is on the top among these
five elements in Group 2A.
C. Incorrect.
Feedback
Electron affinity decreases down a group. Strontium is not on the top among these
five elements in Group 2A.
D. Incorrect.
Electron affinity decreases down a group. Barium is not on the top among these
five elements in Group 2A.
Electron affinity decreases down a group. These are Group 2A elements ranked as
Mg, Ca, Sr, Ba and Ra. Mg is on the top with the highest electron affinity, i.e. the
most energy released when an electron is added to this atom.
The correct answer is (B).
Solution
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Question No. 10 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
10. Ions may be larger or smaller than the neutral atom, depending on the ion’s
charge. Which of the following has the largest radius?
Question
(A) F
(B) F(C) F+
(D) They are the same.
A. Incorrect.
The addition of electrons causes an atom to expand outward. The neutral atom is
smaller than its anion.
B. Correct.
The addition of electrons causes an atom to expand outward. F- has the largest
radius.
C. Incorrect.
Feedback
The addition of electrons causes an atom to expand outward. The anion is larger
than its cation of the same element.
D. Incorrect.
Their sizes rank in descending order: F-, F and F+. The addition of electrons causes
an atom to expand outward.
The addition of electrons causes an atom to expand outward. The anion F- has the
largest radius among them.
The correct answer is (B).
Solution
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