Download 1.2 Reinforce Key Concepts

ELEMENTS MAKE UP THE PERIODIC TABLE.
BIG IDEA A
CHAPTER 1
1.2 Reinforcing Key Concepts
substance’s atomic structure determines its physical and chemical
properties.
KEY CONCEPT
Elements make up the periodic table.
In the 1860s, Dmitri Mendeleev created a
way of listing the elements in a chart. Explain how Mendeleev’s chart was organized.
1. Elements can be organized by similarities.
2. The periodic table organizes the atoms of the elements by properties and
atomic number. In the modern periodic table, elements with similar properties are found
Copyright © by McDougal Littell, a division of Houghton Mifflin Company
in
columns, not rows, and elements are not arranged by atomic mass but by atomic number. Use
the portion of the periodic table shown below to answer questions a–e.
90
91
92
93
94
Th
Pa
U
Np
Pu
Thorium
Protactinium
Uranium
Neptunium
Plutonium
232.038
231.036
238.029
(237)
(244)
a. What
b. How
is the chemical symbol for the element neptunium? ____________
many electrons are found in one atom of this element? ____________
c. What
is the mass of one atom of protactinium? ____________ What is its atomic
number? ____________
d. How
many fewer protons are found in thorium than in uranium? ____________
How do you know? ____________
e. Are these elements gases or solids? ____________ How do you know?
CHEMICAL INTERACTIONS, CHAPTER 1, REINFORCING KEY CONCEPTS 31
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Atomic Structure and the Periodic Table
SECTION