15
3
The Periodic Table
3
section ●
Transition Elements
What You’ll Learn
■
properties of some
transition elements
■ how to tell lanthanides
from actinides
Study Coach
Make Flash Cards As you
read, make flash cards to help
you learn the transition
elements. On one side of the
card, write the name of the
element, its symbol, and its
atomic number. On the other
side of the card, write one
important use of the element.
Before You Read
Name three things you use every day that are made
from metals.
Read to Learn
The Metals in the Middle
Groups 3–12 are called the transition elements. All of
them are metals. The properties of the transition elements
change less as you move across a period than they do for
the representative elements.
Most transition elements are found combined with other
elements in ores. An ore is a mineral that is found naturally
on Earth. A few transition elements like gold and silver are
found as pure elements.
What is the iron triad?
D Organize Information
●
Make the following Foldable to
help you organize information
about the iron triad, transition
metals, lanthanides, and
actinides.
The Iron
Triad
Transition
Metals
Lanthanides
Actinides
232
The Periodic Table
Iron, cobalt, and nickel are in
Iron
Cobalt
Nickel
period 4 and are known as the
26
27
28
Fe
Co
Ni
iron triad. They are shown in the
figure. They have very similar
properties. These elements and
others have magnetic properties. Large magnets are made
from a mixture of nickel, cobalt, and aluminum.
The iron triad also has many other uses. Nickel is used in
batteries along with cadmium. Iron is a necessary part of
hemoglobin, the substance that moves oxygen in your blood.
Iron is mixed with other metals and with carbon to create
steels with different properties. Bridges and skyscrapers are
built with steel because it is strong.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
chapter
How are transition elements used?
Look at the figure below. The transition elements are in
the middle of the periodic table. They are Groups 3–12.
Most transition metals have higher melting points than the
representative elements. The filaments of lightbulbs are
made with tungsten, element 74. Tungsten has the highest
melting point of any metal (3,410°C). Tungsten will not
melt when a current passes through it.
Picture This
1.
Identify How many
periods of transition
elements are there in the
periodic table?
2.
Describe Which group
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Transition Metals
Mercury Mercury has the lowest melting point of any metal
(–39°C). It is used in thermometers and barometers. It is
the only metal that is liquid at room temperature. Like
many of the heavy metals, mercury is poisonous to living
things. It must be handled carefully.
Chromium The name chromium comes from the Greek
word chroma. It means color. Chromium is a colorful
element. Many other transition elements also combine to
make colorful substances.
Platinum Group Ruthenium, rhodium, palladium, osmium,
iridium, and platinum are sometimes called the platinum
group. They have similar properties. They do not combine
easily with other elements. So, they can be used as
catalysts.
What is a catalyst?
A catalyst is a substance that can make something
happen faster. However, the catalyst is not changed. Other
transition elements like nickel, zinc, and cobalt can be used
as catalysts. Transition elements are used as catalysts to
make electronics, plastics, and medicines.
of elements can be used as
catalysts?
Reading Essentials
233
Lanthanide Series
58
Ce
59
Pr
60
Nd
61
Pm
62
Sm
63
Eu
64
Gd
65
Tb
66
Dy
67
Ho
68
Er
69
Tm
70
Yb
71
Lu
Actinide Series
90
Th
91
Pa
92
U
93
Np
94
Pu
95
Am
96
Cm
97
Bk
98
Cf
99
Es
100
Fm
101
Md
102
No
103
Lr
Applying Math
3.
Calculate How many
lanthanide and actinide
elements are there
altogether?
Inner Transition Elements
There are two series of inner transition elements. The
lanthanides is the name of the first series of inner transition
elements. The lanthanides go from cerium to lutetium. The
lanthanides also are called the rare earths because at one
time people thought they were not common. They are
usually found combined with oxygen in Earth’s crust. The
actinides is the name of the second series of inner transition
elements. The actinides go from thorium to lawrencium. The
figure above shows the lanthanides and the actinides.
4.
Explain Why are
lanthanides in the same ore
hard to separate?
The lanthanides are soft metals. They can be cut with a
knife. The lanthanides often are found in the same ore.
They are so much alike that they are hard to separate when
they are in the same ore. Lanthanides are not as rare as
people once thought. Earth’s crust has more cerium than
lead. Cerium makes up 50 percent of a mixture called misch
(MIHSH) metal. Flints in lighters are made from misch
metal. Lighters are used to start fires. Lanthanum, iron, and
neodymium also are in flint.
Lanthanides also are used in color TV screens. A blend of
some lanthanide elements will give off a bright red light.
Other compounds are used to make the other colors for a
natural-looking picture on the screen.
What are the actinides?
All the actinides are radioactive. The nuclei of atoms of
radioactive elements are unstable. They break down to make
other elements. Thorium, protactinium, and uranium are
the only actinides that now are found naturally on Earth.
Uranium is found in Earth’s crust.
All other actinides are synthetic elements. Synthetic
elements are made in laboratories and in nuclear reactors.
Synthetic elements have many uses. Plutonium is used as a
fuel in nuclear power plants. Americium is used in home
smoke detectors. Californium-252 is used to kill cancer cells.
234
The Periodic Table
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are the lanthanides?
How can scientists make synthetic elements?
Scientists can make synthetic elements by using a device
called a particle accelerator. In the particle accelerator, the
nuclei of atoms are made to crash into each other at high
speeds. Some of the nuclei might stick together to make
new, heavier elements. Some of the synthetic elements are
very unstable. Synthetic elements may only last a fraction of
a second before they break down into other elements.
What elements do dentists use?
5.
Explain What happens
to synthetic elements when
they break down?
6.
Analyze Why do you
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
For over 150 years, dentists have used a substance called
amalgam to fill cavities in decayed teeth. Amalgam is a
mixture of silver, copper, tin, and mercury. Some people are
worried that amalgam is harmful because it contains
mercury. Today, dentists can use things other than amalgam
to fill cavities. New materials are used to fix decayed,
broken, or missing teeth. These new materials are strong.
Body fluids will not break them down. They can also be
changed to match the natural color of the tooth. Some of
the new materials have fluoride in them. Fluoride protects
teeth from more decay.
Bonding Agents To use these new materials, dentists use
new bonding agents. Bonding agents are like glue. They glue
the materials to the natural tooth. The bonding agents must
be strong and not be broken down by body fluids.
Braces Orthodontists, dentists who straighten teeth, use
new nickel and titanium alloys for the wires on braces.
These wires have shape memory. This means they will
always try to keep their shape. The wires are heated to lock
in their shapes. The wires are forced out of shape when they
are put on crooked teeth. They will try to return to their
original shape, straightening the teeth as they do.
think wires that hold their
shape are useful for fixing
crooked teeth?
Reading Essentials
235
After You Read
Mini Glossary
actinides: the name of the second series of inner
transition elements
catalyst: a substance that can make something happen
faster, but not change itself
lanthanides: the name of the first series of inner
transition elements
synthetic elements: elements made in laboratories and in
nuclear reactors
1. Review the terms and their definitions in the Mini Glossary. Write a sentence describing
why you would add a catalyst to something.
2. Complete the table. In the second column, write whether each element is a regular
transition element, a lanthanide, or an actinide. Write a use for the element in the
third column.
Element
Element Group
Use
Cerium
Tungsten
Iron
3. You were asked to make flash cards of the transition elements. What is another method
you could use to learn the transition elements?
End of
Section
236
The Periodic Table
Visit blue.msscience.com to access your textbook, interactive
games, and projects to help you learn more about transition
elements.
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Plutonium