chapter
15
3
The Periodic Table
1
section ●
Introduction to the Periodic Table
Before You Read
Write what you think an element is on the lines below.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Development of the Periodic Table
People who lived long ago knew about a few of the
substances that are now called elements. They used gold and
silver to make coins and jewelry. They used copper, tin, and
iron to make tools. By 1830, scientists had found and named
55 different elements. The list of elements is still growing.
What You’ll Learn
■
the history of the
periodic table
■ how to read an
element key
■ how the periodic table
is organized
Identify Vocabulary
Highlight each vocabulary term
you read in this section. Also,
highlight the definition of each
term. After you read the section,
go back and read the vocabulary
terms and their definitions
again.
What was Mendeleev’s table of elements?
Dmitri Mendeleev (men duh LAY uhf) was a Russian
chemist. In 1869, he published his first periodic table.
Mendeleev arranged the elements according to increasing
atomic mass. Elements with similar properties made groups.
Not all of the elements were known. So, Mendeleev left three
spaces for missing elements. He predicted what the missing
elements were like. Within 15 years, all three elements were
found. They were gallium, scandium, and germanium.
How did Moseley add to the periodic table?
In the early 1900s, the English physicist Henry Moseley
rearranged Mendeleev’s table. He arranged the elements
according to atomic number instead of atomic mass.
Moseley put the elements in order of increasing number of
protons in the nucleus. With Moseley’s table, it was easy to
see how many elements still had not been discovered.
A Compare and Contrast
●
Make the following Foldable to
compare and contrast how
Mendeleev and Moseley arranged
the periodic table.
Mendeleev
Moseley
Reading Essentials
221
Today’s Periodic Table
Today, the elements are still organized by increasing
atomic number. Look at the periodic table at the back of
your textbook. The periods, or rows, are labeled 1–7. A
period is a row of elements whose properties change
gradually. The periodic table has 18 columns. Each column
has a group, or family, of elements. A group has elements
that have similar physical or chemical properties.
How is the periodic table divided?
The periodic table can be divided into parts. Look at the
figure below. The representative elements are the elements in
Groups 1 and 2 and the elements in Groups 13–18. They
include metals, metalloids, and nonmetals. The transition
elements are the elements in Groups 3–12. They are all
metals. Some transition elements are placed below the main
table. These inner transition elements are called the lanthanide
and actinide series. One series follows the element lanthanum,
element 57. The other series follows actinium, element 89.
1.
Identify What are the
elements in Groups 3–12
called?
Representative elements
Representative
elements
Inner transition elements
Lanthanide series
Picture This
2.
Actinide series
Label Number the
groups of representative
and transition elements
from left to right. Start in
the top row of the
representative elements on
the far left.
222
The Periodic Table
What are metals?
The periodic table is divided into metals, nonmetals, and
metalloids. Examples of a metal, a nonmetal, and a
metalloid are shown in the figure near the top of the next
page. All of the metals except for mercury are solids. Most
metals have high melting points. A metal is an element that
has luster, is a good conductor of heat and electricity, is
malleable (MAL yuh bul), and is ductile (DUK tul).
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Transition elements
Metal Properties Luster is the ability to reflect light. A
good conductor of heat and electricity lets heat and
electricity pass through it easily. Something that is malleable
can be shaped easily into objects or pounded into thin
sheets. Something that is ductile can be stretched into wire.
Boron, a metalloid, has a slight luster and conducts electricity
at high temperatures like a metal. But like a nonmetal, boron
is brittle and does not conduct electricity well at low temperatures.
Carbon is a nonmetal. In graphite,
carbon is a soft, brittle solid. It is not
reflective, ductile, or malleable.
Copper, a metal, is reflective,
ductile, malleable, and a
good conductor of heat and
electricity.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are nonmetals and metalloids?
Nonmetals are usually gases or brittle solids at room
temperature. They do not conduct heat and electricity well.
Brittle solids break apart easily. Carbon, sulfur, nitrogen, oxygen, and phosphorus are nonmetals that are necessary for life.
The elements between metals and nonmetals on the
periodic table are metalloids (ME tuh loydz). A metalloid is
an element that shares some properties with metals and
some with nonmetals. They are also called semimetals.
Picture This
3.
Identify Which of the
elements in the figure
conducts heat well?
What does an element key show?
Each element on the periodic
Hydrogen
Element
table has an element key. The
1
Atomic number
key shows the name of the
H
Symbol
element, its atomic number, its
1.008
Atomic mass
symbol, and its average atomic
mass. The figure shows the
State of matter
element key for hydrogen.
Element keys also have symbols that show an element’s state
of matter at room temperature. Gases are marked with a
balloon. Solids are marked with a cube. Liquids are marked
with a drop. The elements that are not found naturally on
Earth, or synthetic elements, are marked with a bull’s-eye.
B Draw and Label Use a
●
quarter-sheet of paper to make
an element key for hydrogen.
Label each part of the element
key.
Hydrogen
1
H
1.008
Reading Essentials
223
What are element symbols?
The symbols for the elements are either one or two letters,
often based on the element’s name. For example, V is the
symbol for vanadium and Sc is the symbol for scandium.
Sometimes the symbols do not match the names. Ag is the
symbol for silver and Na is the symbol for sodium. In those
cases, the symbols might come from Greek or Latin names
for the elements. Some elements are named for scientists
such as Lise Meitner (meitnerium, Mt). Some are named for
geographic locations such as France (francium, Fr).
4.
Identify How many
letters do element symbols
in the periodic table have?
New Elements Newly discovered elements are given a
temporary name and three-letter symbol. The symbol is
related to the element’s atomic number. The International
Union of Pure and Applied Chemistry (IUPAC) started
using this system in 1978. When the discovery of an element
is confirmed, the discoverers can choose a name. The table
shows where some element names and symbols come from.
Chemical Symbols and Their Origins
Picture This
5.
Explain Why is the
symbol for gold Au instead
of G?
224
The Periodic Table
Syymbool
Where the Name Comes From
Mendellevium
Md
For Dim
mitri Mendeleev
Lead
Pb
The Latin name for lead
is plumbbum.
Thorium
m
Th
The Norrse god of thunder is Thor.
Poloniuum
Po
For Polaand, where Marie Curie,
a famouus scientist, was born
Hydroggen
H
From Grreek words meaning
“water fformer.”
Mercuryy
Hg
Hydrarggyrum means
“liquid ssilver” in Greek.
Gold
Au
Aurum means
m
“shining dawn”
in Latin.
Unununnium
Uuu
Named using the IUPAC
namingg system.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Name
After You Read
Mini Glossary
group: a collection of elements that have similar physical or
chemical properties
metal: an element that has luster, is a good conductor of
heat and electricity, is malleable, and is ductile
metalloid: an element that shares some properties with
metals and some with nonmetals
nonmetals: elements that are gases or brittle solids at room
temperature and do not conduct heat and electricity well
period: a row of elements whose properties change gradually
representative elements: the elements in Groups 1 and
2 and the elements in Groups 13–18
transition elements: the elements in Groups 3–12
1. Read the key terms and definitions in the Mini Glossary above. Write a sentence that tells
how to locate a period and a group on the periodic table of elements.
2. In the Venn diagram, write properties of metals and nonmetals. In the middle, write the
name of the group that has properties of both.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Metals
Nonmetals
3. How would you explain to an elementary school student what the periodic table is?
Visit blue.msscience.com to access your textbook, interactive
games, and projects to help you learn more about the
periodic table.
End of
Section
Reading Essentials
225