Groups with Metalloids
Jean Brainard, Ph.D.
Say Thanks to the Authors
Click http://www.ck12.org/saythanks
(No sign in required)
To access a customizable version of this book, as well as other
interactive content, visit www.ck12.org
CK-12 Foundation is a non-profit organization with a mission to
reduce the cost of textbook materials for the K-12 market both
in the U.S. and worldwide. Using an open-content, web-based
collaborative model termed the FlexBook®, CK-12 intends to
pioneer the generation and distribution of high-quality educational
content that will serve both as core text as well as provide an
adaptive environment for learning, powered through the FlexBook
Platform®.
Copyright © 2015 CK-12 Foundation, www.ck12.org
The names “CK-12” and “CK12” and associated logos and the
terms “FlexBook®” and “FlexBook Platform®” (collectively
“CK-12 Marks”) are trademarks and service marks of CK-12
Foundation and are protected by federal, state, and international
laws.
Any form of reproduction of this book in any format or medium,
in whole or in sections must include the referral attribution link
http://www.ck12.org/saythanks (placed in a visible location) in
addition to the following terms.
Except as otherwise noted, all CK-12 Content (including CK-12
Curriculum Material) is made available to Users in accordance
with the Creative Commons Attribution-Non-Commercial 3.0
Unported (CC BY-NC 3.0) License (http://creativecommons.org/
licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated
herein by this reference.
Complete terms can be found at http://www.ck12.org/terms.
Printed: February 8, 2015
AUTHOR
Jean Brainard, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Groups with Metalloids
1
Groups with Metalloids
• Identify elements in groups 13–16 of the periodic table.
• List properties of a metalloid from each of these groups.
This image represents a famous ancient Egyptian named Tutankhamen. Do you see his heavy eyeliner? Most
likely the eyeliner was made of a mineral containing antimony. This metalloid was commonly used for makeup by
Egyptians between four and five thousand years ago. Today we know that antimony is toxic, although Tutankhamen
probably didn’t know that. Antimony is found in group 15 of the periodic table. Group 15 is one of four groups of
the periodic table that contain metalloids.
Groups 13–16
Groups 13–16 of the periodic table (orange in the Figure 1.1) are the only groups that contain elements classified
as metalloids. Unlike other groups of the periodic table, which contain elements in just one class, groups 13–16
contain elements in at least two different classes. In addition to metalloids, they also contain metals, nonmetals, or
both. Groups 13–16 fall between the transition metals (in groups 3–12) and the nonmetals called halogens (in group
17).
What Are Metalloids?
Metalloids are the smallest class of elements, containing just six members: boron (B), silicon (Si), germanium
(Ge), arsenic (As), antimony (Sb), and tellurium (Te). Metalloids have some properties of metals (elements that can
conduct electricity) and some properties of nonmetals (elements that cannot conduct electricity). For example, most
metalloids can conduct electricity, but not as well as metals. Metalloids also tend to be shiny like metals, but brittle
like nonmetals. Chemically, metalloids may behave like metals or nonmetals, depending on their number of valence
electrons. You can learn more about specific metalloids by clicking on the element symbols in the periodic table at
this URL: http://www.chemicool.com/ .
1
www.ck12.org
FIGURE 1.1
Q: Why does the chemical behavior of an element depend on its number of valence electrons?
A: Valence electrons are the electrons in an atom’s outer energy level that may be involved in chemical reactions
with other atoms.
Group 13: Boron Group
Group 13 of the periodic table is also called the boron group because boron (B) is the first element at the top
of the group (see Figure 1.2). Boron is also the only metalloid in this group. The other four elements in the
group—aluminum (Al), gallium (Ga), indium (In), and thallium (Tl)—are all metals. Group 13 elements have three
valence electrons and are fairly reactive. All of them are solids at room temperature.
Group 14: Carbon Group
Group 14 of the periodic table is headed by the nonmetal carbon (C), so this group is also called the carbon group.
Carbon is followed by silicon (Si) and germanium (Ge) ( Figure 1.3), which are metalloids, and then by tin (Sn)
and lead (Pb), which are metals. Group 14 elements group have four valence electrons, so they generally aren’t very
reactive. All of them are solids at room temperature.
2
www.ck12.org
Chapter 1. Groups with Metalloids
FIGURE 1.2
Boron is a very hard, black metalloid with
a high melting point. In the mineral called
borax, it is used to wash clothes.
In
boric acid, it is used as an eyewash and
insecticide.
FIGURE 1.3
Germanium is a brittle, shiny, silverywhite metalloid.
Along with silicon, it
is used to make the tiny electric circuits on computer chips. It is also used
to make fiber optic cables—like the one
pictured here—that carry telephone and
other communication signals.
Group 15: Nitrogen Group
Group 15 of the periodic table is also called the nitrogen group. The first element in the group is the nonmetal
nitrogen (N), followed by phosphorus (P), another nonmetal. Arsenic (As) ( Figure 1.4) and antimony (Sb) are the
metalloids in this group, and bismuth (Bi) is a metal. All group 15 elements have five valence electrons, but they
vary in their reactivity. Nitrogen, for example, is not very reactive at all, whereas phosphorus is very reactive and
found naturally only in combination with other substances. All group 15 elements are solids, except for nitrogen,
which is a gas.
Group 16: Oxygen Group
Group 16 of the periodic table is also called the oxygen group. The first three elements—oxygen (O), sulfur (S), and
selenium (Se)—are nonmetals. They are followed by tellurium (Te) ( Figure 1.5), a metalloid, and polonium (Po), a
3
www.ck12.org
FIGURE 1.4
The most common form of the metalloid
arsenic is gray and shiny.
Arsenic is
extremely toxic, so it is used as rat poison.
Surprisingly, we need it (in tiny amounts)
for normal growth and a healthy nervous
system.
metal. All group 16 elements have six valence electrons and are very reactive. Oxygen is a gas at room temperature,
and the other elements in the group are solids.
FIGURE 1.5
Tellurium is a silvery white, brittle metalloid.
It is toxic and may cause birth
defects. Tellurium can conduct electricity
when exposed to light, so it is used to
make solar panels. It has several other
uses as well. For example, it makes steel
and copper easier to work with and lends
color to ceramics.
Q: With six valence electrons, group 16 elements need to attract two electrons from another element to have a stable
electron arrangement of eight valence electrons. Which group of elements in the periodic table do you think might
form compounds with elements in group 16?
A: Group 2 elements, called the alkaline Earth metals, form compounds with elements in the oxygen group. That’s
because group 2 elements have two valence electrons that they are “eager” to give up. An example of a group 2 and
group 6 compound is calcium oxide (CaO).
Summary
• Groups 13–16 of the periodic table contain one or more metalloids, in addition to metals, nonmetals, or both.
4
www.ck12.org
Chapter 1. Groups with Metalloids
• Group 13 is called the boron group, and boron is the only metalloid in this group. The other group 13 elements
are metals.
• Group 14 is called the carbon group. This group contains two metalloids: silicon and germanium. Carbon is
a nonmetal, and the remaining elements in this group are metals.
• Group 15 is called the nitrogen group. The metalloids in this group are arsenic and antimony. Group 15 also
contains two nonmetals and one metal.
• Group 16 is called the oxygen group. Tellurium is the only metalloid in this group, which also contains three
nonmetals and one metal.
Explore More
Watch the video at the following URL, and then answer the questions below.
http://www.youtube.com/watch?v=NO36yksPOBM (6:50)
MEDIA
Click image to the left or use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/54889
1. Why does boron act chemically like a metal?
2. Why do arsenic, antimony, and tellurium tend to have chemical properties similar to nonmetals?
3. Sometimes silicon and germanium behave like metals, and sometimes they behave like nonmetals. Explain
why.
Review
1.
2.
3.
4.
Which elements in groups 13–16 are metalloids?
Name two physical properties that boron shares with most metals.
What property of the metalloid silicon makes it useful for computer chips?
A recent investigation found relatively high levels of the metalloid arsenic in samples of apple juice. Why
might this be a serious problem?
5. Why is the metalloid tellurium used to make solar panels?
References
1. Christopher Auyeung. The periodic table . CC BY-NC 3.0
2. Christopher Auyeung and Laura Guerin. Boron is used in borax and boric acid . CC BY-NC 3.0
3. Cable: Savannah River Site; Illustration: Christopher Auyeung. Germanium is used in fiber optic cables .
Cable: CC BY 2.0; Illustration: CC BY-NC 3.0
4. Christopher Auyeung and Laura Guerin. Arsenic is used in rat poison . CC BY-NC 3.0
5. Solar panel: User:ChristofferRiemer/Wikimedia Commons; Illustration: Christopher Auyeung. Tellurium is
used in solar panels . Solar panel: CC BY 3.0; Illustration: CC BY-NC 3.0
5