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Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
57
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 6
To summarize, phosphorus is found in period 3, group 15, and the
p-block of the periodic table. A glance at the table will confirm this
answer.
Practice Problems
11. Without using the periodic table, determine the group, period,
and block in which an element with each of the following electron configurations is found.
a. [He]2s 2 2p 5
c. [Kr]5s 2 4d 10 5p 3
b. [Ar]4s 2
d. [Ar]4s 2 3d 3
12. Write the electron configuration of the following elements.
a. the alkaline earth element in the sixth period
b. the halogen in the third period
c. the group 14 element in the third period
d. the group 5 element in the fourth period
e. the group 1 element in the fifth period
6.3 Periodic Trends
The electron structure of an atom determines many of its chemical
and physical properties. Because the periodic table reflects the electron configurations of the elements, the table also reveals trends in
the elements’ chemical and physical properties.
Atomic radius The atomic radius is a measure of the size of an
atom. The larger the radius, the larger is the atom. Research shows
that atoms tend to decrease in size across a period because the nuclei
are increasing in positive charge while electrons are being added to
sublevels that are very close in energy. As a result, the increased
nuclear charge pulls the outermost electrons closer to the nucleus,
making the atom smaller.
Moving down through a group, atomic radii increase. Even
though the positive charge of the nucleus increases, each successive
element has electrons in the next higher energy level. Electrons in
these higher energy levels are located farther from the nucleus than
those in lower energy levels. The increased size of higher energy
level outweighs the increased nuclear charge. Therefore, the atoms
increase in size.
▲
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
57
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 6
To summarize, phosphorus is found in period 3, group 15, and the
p-block of the periodic table. A glance at the table will confirm this
answer.
Practice Problems
11. Without using the periodic table, determine the group, period,
and block in which an element with each of the following electron configurations is found.
a. [He]2s 2 2p 5
c. [Kr]5s 2 4d 10 5p 3
b. [Ar]4s 2
d. [Ar]4s 2 3d 3
12. Write the electron configuration of the following elements.
a. the alkaline earth element in the sixth period
b. the halogen in the third period
c. the group 14 element in the third period
d. the group 5 element in the fourth period
e. the group 1 element in the fifth period
6.3 Periodic Trends
The electron structure of an atom determines many of its chemical
and physical properties. Because the periodic table reflects the electron configurations of the elements, the table also reveals trends in
the elements’ chemical and physical properties.
Atomic radius The atomic radius is a measure of the size of an
atom. The larger the radius, the larger is the atom. Research shows
that atoms tend to decrease in size across a period because the nuclei
are increasing in positive charge while electrons are being added to
sublevels that are very close in energy. As a result, the increased
nuclear charge pulls the outermost electrons closer to the nucleus,
making the atom smaller.
Moving down through a group, atomic radii increase. Even
though the positive charge of the nucleus increases, each successive
element has electrons in the next higher energy level. Electrons in
these higher energy levels are located farther from the nucleus than
those in lower energy levels. The increased size of higher energy
level outweighs the increased nuclear charge. Therefore, the atoms
increase in size.
▲