111 / 123
PRACTICE
Problems
8.
Without using the periodic table, determine the group, period, and block of an atom with the
following electron configurations.
a.
[Ne]3s
2
b.
[He]2s
2
c.
[Kr]5s
2
4d
10
5p
5
9.
What are the symbols for the elements with the following valence electron configurations?
a.
s
2
d
1
b.
s
2
p
3
c.
s
2
p
6
10. CHALLENGE
Write the electron configuration of the following elements.
a.
the group 2 element in the fourth period
b.
the group 12 element in the fourth period
c.
the noble gas in the fifth period
d.
the group 16 element in the second period
The development of the periodic table took many years, but like all scientific knowl-
edge, it is open to change. As new elements are synthetized, identified, and named, and
as new data about elements arise from experimentation, the periodic table is updated.
Refer to
Figure 10
on the previous page to learn more about the history of the periodic
table and the work of the many scientists who contributed to its development. The
periodic table is an essential tool in understanding and exploring chemistry and you
will use it throughout your study of the subject.
Go online to follow your personalized learning path to review, practice,
and reinforce your understanding.
Check Your Progress
Summary
• The periodic table has four
blocks (s, p, d, f).
• Elements within a group have
similar chemical properties.
• The group number for
elements in groups 1 and 2
equals the element’s number
of valence electrons.
• The energy level of an atom’s
valence electrons equals its
period number.
Demonstrate Understanding
11.
Explain
what determines the blocks in the periodic
table.
12.
Determine
in which block of the periodic table are the
elements having the following valence electron
configurations.
a. s
2
p
4
c. s
2
d
1
b. s
1
d. s
2
p
1
13.
Infer
Xenon, a nonreactive gas used in strobe lights,
is a poor conductor of heat and electricity. Would you
expect xenon to be a metal, a nonmetal, or a metal-
loid? Where would you expect it to be on the periodic
table? Explain.
14.
Explain
why elements within a group have similar
chemical properties.
15.
Model
Make a simplified sketch of the periodic table,
and label the s-, p-, d-, and f-blocks.
ADDITIONAL PRACTICE
Lesson 2 • Classification of the Elements
151