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Review 3
Lesson 9.1: Metallic Compounds 5 Objective 5 Warm-Up
5 Learn about It 6 Key Points 9 Web Links
10 Check Your Understanding 10 Challenge Yourself
12
Lesson 9.2: Properties of Metallic Compounds 13 Objectives
13 Warm-Up 13 Learn about It 14 Key Points
19 Web Links 19 Check Your Understanding 20
Challenge Yourself 21
Laboratory Activity 22
Performance Task 24
Self Check 26
Key Words 26
Wrap Up 28
Unit 9 Metallic Bonding
conductors of electricity and heat. Furthermore, their ability to
be drawn into thin
wires and to be hammered
into thin sheets show that the bonds between two
metallic atoms are strong yet flexible. Alloys
used in airplane turbines and
conductors in
electrical cells are just few examples of fantastic materials we
can
derive from metals. But
why are metals capable of these things? Why can copper, for
example, exhibit
ductility and be
drawn into thin wires? In this unit, you will learn about how
metals
are
structured, and how do their structures explain their wonderful
properties. This
unit describes the another type
of chemical bonding known as metallic bonding
which is present between metals. Ultimately, this chapter will help
you distinguish
different types of compounds
based on some properties that differentiate metallic,
ionic and covalent compounds.
Essential Questions
At the end of this unit, you should be able to answer the
following questions.
Review
An element is composed of only one kind of atom. It can be
classified as
metals,
nonmetals, and metalloids. Compounds are substances made up
of
at least two or more elements chemically
combined.
Valence electrons are the most important electrons of an element,
mainly
because they are directly involved in bonding.
These are electrons found at
the outermost
shell of an atom which are lost, gained or shared to satisfy
octet.
o A cation is a positively-charged atom, as a result of losing at
least one
electron in its valence
shell.
o Anion – negatively-charged atom, as a result of gaining at least
one
electron in its valence shell.
Covalent compounds are compounds that form as a result of
covalent
bonding, wherein two atoms share their valence
electrons.
describe the electron sea model of metals.
Metals can be distinguished from nonmetals based on their
properties. Metals are
electrically and
thermally conductive, and they are also malleable, ductile
and
lustrous, unlike nonmetals. These properties can be
explained by the structure of
metallic
compounds. Metallic compounds, or simply metals, are held together
by
metallic bonds. How are metals bonded
together?
Warm-Up Metallic Bonding Metallic bonding
exists between two metals. Let us consider the case where the
metals are identical. Let us look at an
aluminum atom. Fill up the table below.
Chemical element Aluminum
Valence electron configuration
Lewis electron-dot formula
1. Based on your answers for the table above, what is the
easiest way
aluminum could attain an octet?
________________________________________________________________________________
________________________________________________________________________________
3. Based from your answer on number 2, is it possible for two
aluminum atoms to form a covalent compound? Why or why
not?
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________________________________________________________________________________
Learn about It
hand, sharing electrons is also not an option. Even if they share
all electrons from
both
metals, they will still lack some electrons to complete the octet.
Representative
metals are known to obey
octet rule, and this inconsistency suggests that covalent
bonding is not also suitable to explain the
interaction between them. This opens up
the idea that most likely, a third type of bonding is
involved. The Electron Sea Model The atoms
in a metal, when they bond together, form a metallic bond. In a
metallic
bond, the
valence shells of a component atom overlaps with another one, much
like
in a covalent bond. However,
unlike a covalent compound which only involves a few
atoms to form a bond, multiple metal atoms
surround each other in order to share
their valence electrons simultaneously. This happens
when a metal atom starts
freeing valence electron to move
around and create a domino effect to its
neighboring electrons. Although the metal which loses the electron
becomes
incompletely filled, the vacated spot will be
completely filled by another moving
electron.
In this scenario, electrons are said to be delocalized, or free to
move from
one atom to
another. This results to a picture of bonding, wherein metallic
cations,
are fixed and embedded in
a lattice surrounded by a sea of valence electrons. This
is depicted in the following
illustration.
Fig. 1. Metallic bonding. Metal cations embedded in a sea of
valence electrons.
Metallic bonding is not limited to one type of metal.
Alloys, or solid homogeneous
mixtures of metals, are formed by mixing two different metals
together. Alloys
modify properties of the
original metal, enhancing strength, conductivity, or any
other way depending on the application.
Copyright © 2018 Quipper Limited 6
Substitutional alloys, are alloys in which the atoms of one
element substitute for
the atoms of the
other element in the alloy. This occurs when two metals of
roughly
the same
atomic size are mixed together. Examples of this alloy are
brass
(combination of copper and zinc) and
bronze (combination of copper and
aluminum).
Fig 2. Substitutional alloy.
Interstitial alloys, on the other hand, are alloys in which
the atoms of one element
is
placed in between the spaces of the atoms of the other element.
This occurs
when one metal’s
atoms are smaller than the atoms of the other metal. An
example
of interstitial
alloys is steel, which is a combination of iron and
carbon.
Fig 3. Interstitial alloy.
Examples of alloys and their uses are listed below.
Table 9.1. Various types and uses of alloys. Alloy
Combination of metal Uses
Bronze Copper and aluminum Used in sculptures,
musical instruments, and
medals
automobiles and appliances
Brass Copper and zinc Used in plumbing, musical
instruments, and
home furnitures
Amalgam Mercury and silver Used in electrolytic
cells, extraction of gold, and dentistry (cavity
filler)
Pewter Tin and antimony Used in decoration,
jewelry, and tableware
Solder Tin and lead Used in connecting electronic
parts and
plumbing
Metallic bonding is formed when metal atoms free their valence
electrons,
producing a sea of electrons which they can
all share.
Alloys are solid homogeneous mixtures of metals formed by mixing
two
different metals together.
Substitutional alloys are alloys in which the atoms of one
element
substitute for the atoms of the other element
in the alloy.
Check Your Understanding
A. Write true if the statement is true. Otherwise, write
false.
4. Metallic bonding between atoms occur because of valence shell
overlap
between multiple atoms.
5. Metallic bonding allows inner core electrons, as well as valence
electrons, to
freely move about.
B. Assess whether the following sentences describe a
substitutional or an
interstitial alloy. Write S if the sentence describes a
substitutional alloy. Write I
if the
sentence describes an interstitial alloy. Write A if the sentence
describes
both alloy type. Write N if it
doesn’t describe an alloy.
1. A piece of solid is made up of positively-charged copper and
negatively- charged chlorine.
2. Alloys modify properties of the original metal, enhancing both
strength and
conductivity,
3. Brass is an example of this alloy. 4. This type of alloy
is made up of atoms with relatively similar sizes. 5. These
are solid, homogeneous mixtures of metals. 6. The
positively-charged ion is surrounded by negatively-charged ions
in
almost all directions. 7. The electrons are collectively
shared between iron and carbon. 8. Multiple bonds are formed
to satisfy the octet between two rhenium atoms. 9. The
protons are moving from one position to another in this type of
alloy. 10.Electrons are delocalized between two metal
atoms.
C. For the next few questions, refer to the figure below.
Answer the next few
questions.
Answer the following questions comprehensively.
1. Steel is a compound of iron and carbon. Why do you think steel
is considered
an alloy,
as opposed to an ionic or covalent compound?
2. Graphene, a 2D sheet of carbon atoms bonded together in a
lattice, is
electrically conductive, harder
than steel, and has a very high melting point.
Despite carbon being a nonmetal, why do you think Graphene
possesses
these properties?
For the following combination of metals, identify what type
of alloy will be formed.
You can
look and compare the sizes of the ions that can form from each
metals to
identify the type of alloy.
3. Cu and Al 4. Hg and Ag
Objectives In this lesson, you should be able
to:
explain the properties of metals in terms of the electron sea
model; and
Making a Sea of Electron Materials:
5 pieces each of red and blue balls, of different sizes 5 ft.
wires glue or adhesives
Learn about It
Conductivity Conductivity is the ability of a material
to allow heat or electric current to easily
pass through. Electricity, on the other hand,
is the flow of electric charge brought
by the movement of electrons. Whenever electricity or heat
passes through metals,
it can freely flow
without much obstruction from the positive nuclei of atoms.
Hence, metals and alloys are electrically and
thermally conductive.
Fig 4. Cooking pans are made up of metals which can transfer
heat.
transfer of electricity. Electrons also carry energy while
travelling which allows the
transfer of
heat. Density and Tensile Strength Metals are
very dense, as shown in the table below. They also have high
tensile
strength, hence
they are used as construction materials. Their high densities
and
high tensile strength suggest that metallic
bond is very strong. This allows the
atoms inside metals to pack tightly, producing rigid
structures.
Table 9.2 Densities of some metals. The density of water is 1
g/cm3.
Metal Density (g/cm3)
Fig 6. High tension wires which hold the tension bridges are
usually made up of
Luster
Key Points
Metals are good conductors of heat and electricity. The
delocalized electrons
allows transfer of electricity, and heat is carried by the
electrons as it travels
from one
place to another.
Metals are very dense and have high tensile strength, indicative of
the
immense strength of metallic
bonds.
Metals have high melting and boiling points. Since metal cations
are
attracted to a sea of electrons, greater energy is
needed to melt and boil
metals.
Metals and alloys are malleable and ductile. When atoms are under
stress,
the delocalized electrons allow for the
metal atoms to simply slide over one
another without breaking the metallic bond.
Check Your Understanding
A. Write true if the statement is true. Write false
otherwise.
1. Metals are ductile and malleable because cations can move about
without
breaking bonds.
2. Metals have high boiling points. 3. Metals can conduct
electricity because electrons can freely move about the
bulk of the metal. 4. Metals do not allow electric current to
flow unimpeded. 5. Metals have low melting points
B. Identify if the following physical properties describe a
metal or not. Write M if it
pertains to a property of metal, and N if not. 1. Electrical
wires are used to transfer electricity from a source to your
household devices. 2. Coal transfers heat to the grilled
liempo. 3. Pencil lead are good conductors of
electricity. 4. Metallic particles float in water. 5.
Metal sheets are found in heating materials and containers.
6. Aluminum foil is used to grill bangus. 7. Diamond conducts
electricity and heat. 8. Oven uses gaseous metal to transfer
heat and bake cakes. 9. Tin cans can be reshaped by
hammering. 10.Liquid mercury conducts electricity even in
liquid form.
Answer the following questions comprehensively. 1.
Differentiate a metallic bond from a covalent bond. 2. Which
of the three bond types do you think is the strongest? Why?
3. Metals form metallic bonds, nonmetals form covalent bonds, and
metals and
nonmetals form ionic bonds. How do you think metalloids form their
bonds? 4. The conductivity of metals at very low temperatures
increases to a point, that
it achieves a state called superconductivity. Based on what you
know about
metallic bonding, why is this
so?
Properties of Metals
Objective At the end of this laboratory activity, the
students should be able to:
observe properties of household metallic compounds.
Materials and Equipment
stainless steel copper wire aluminum foil iron
nail mossy zinc tin can charcoal
hammer ziplock bags water beaker or
container watch glass
Procedure Observation of Physical
Properties
1. Observe the color of stainless steel, copper wire, aluminum
foil, iron nail,
mossy zinc, tin can and
charcoal. Record your observations on the table
below.
2. Similarly, observe if these solids exhibit luster. Record your
observations on
the table below. Put a check mark if
the solid exhibits luster, and cross mark
if the solid does not.
Test for Hardness and Malleability 1. Take a small amount of
steel, copper wire, aluminum foil, iron nail, mossy
zinc, tin can and charcoal on separate ziplock bags. 2. Close
the ziplock bags. Using a hammer, carefully pound the solids inside
the
ziplock bags. Observe what happens to the solids. Continue pounding
until
no more changes occur.
3. Record your observations on the table below. Test
for Conductivity
1. Take a small amount of steel, copper wire, aluminum foil, iron
nail, mossy
zinc and charcoal. Place it in
separate watch glasses.
2. Using an improvised electrical conductivity set-up, test the
conductivity of
each solid. Touch the solids using the loose
ends of the set-up. Observe if the
flashlight or bulb lights up.
Waste Disposal Dispose solids in a regular trash bin.
Dispose all solutions in sink with excessive amount of running
water.
Data and Results (or Observation) Record your
observations on the table below.
Table 1. Properties of household metals.
Household material
Exhibit luster?
Guide Questions
1. Which solids sink on water? What property is this associated
with? 2. Which solids exhibit luster? Explain why these
solids shine with light. 3. What can you say about the
hardness of each solids? Compare it with
charcoal. 4. Which solids are malleable? Explain how can they
be able to resist physical
stress. 5. Which solids are able to light up the bulb?
Explain why they can light up the
bulb even at the solid state.
Performance Task
Knowing the Bond Type Your school launched a weeklong
celebration called The Mystery Week. It’s an event
that fosters skills development, critical thinking
and creativity. The Chemistry
department hosted the main
activity of the week, a brain tickling puzzle about the
identities of three different
solids. You are part of a group of young science
enthusiasts. Your group take the
challenge. The Chemistry department wanted to test your chemistry
skills and
asked you to identify what types of bonds are
present in each solids. Goal
Your task is to design a method in identifying the type of chemical
bond
present in each solid
.
Role You are part of a group of young science
enthusiasts.
Audience
Your audience is the Chemistry department.
Situation
You have three different solids, labelled A, B and C. A is a thin
silver sheet,
while B and C are white powdery solids.
Each solids just weigh exactly 1 gram.
Product/Performance and Purpose:
You will conduct a series of experiment to be able to find out what
types of
bonds are
present in each solid.
You will explain your methods and how did you arrive to the
conclusion on
what type of bond
each solid contains.
Standards and Criteria for Success
Your work must meet the standards found in the rubric below.
Rubrics for Assessment
Criteria Below Expectations 0% to 49%
Needs Improvement 50% to 74%
Successful Performance 75 to 99%
Exemplary Performance 100%
Comprehensiveness Methods does not justify the
objectives
Shows some comprehensive- ness, but most methods
are not in line with the objectives
Comprehensive, some methods meet the objectives
but are not planned well
Very comprehensive, method carefully planned out
and techniques meet the objectives
Reliability Methods produced no data
Shows some reliability, data can be gathered but
cannot be analyzed further
Reliable, data gathering and analysis offers
reliable results but sometimes show
inconsistencies
Shows some originality, inadequate used of
resources
Original ideas, adequate use of resources
Very original, shows imaginative use of
resources
After studying the unit, can you now do the following?
Check I can…
Recognize and explain properties of metals and
alloys
Explain why copper can be drawn in thin
wires
Reflect
Metallic compounds These are compounds made up of
metals.
Delocalized electrons These are electrons which are free to
move from one atom to another.
Alloys These are solid homogeneous mixtures of metals
formed by mixing two different metals together.
Substitutional alloys These are substituted alloys in which
the atoms of one element substitute for the atoms of the
other element in the alloy.
Interstitial alloys These are substituted alloys in which the
atoms of one element is placed in between the spaces of the
atoms of the other element.
Sea of Electron Model This describes metals as metal cations
suspended in a sea of mobile electrons. The electrons are
collectively shared to satisfy octet.
Malleability It is the ability of a material to be formed
into sheets without breaking apart
Clackamas Community College. “Metallic Bonding”. Accessed 3
Jul 2017. http://dl.clackamas.edu/ch104-07/metallic.htm
Chang, Raymond and Kenneth A. Goldsby. 2016. Chemistry. New
York, NY: McGraw-Hill Education. Silberberg,
Martin. 2009. Chemistry: The Molecular Nature of Matter and
Change, 5th edition. Department of
Education, Republic of the Philippines. EASE II Module 14:
The Chemical Bonds. 2014. Republic of the Philippines.