Chapter 6
Ionic Bonding and Ionic
Compounds
Lets Summarize … Who are the
Valence Electrons?
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These are the electrons that are responsible
for the chemical properties of atoms
These are the electrons in the outer energy
level.
Valence electrons are the s and p electrons
in the outermost, or highest energy level
The Number of Valence Electrons is given
by the “A” Group name.
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Recall How to Predict the Ion
Charge?
How Do we Determine the
Valence Electrons??
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So, the Valence Electrons are as follows:
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Group
Group
Group
…
Group
Group
Group
s1
1A – 1 valence electron,
2A – 2 valence electrons, s2
3A – 3 valence electrons, s2p1
6A – 6 valence electrons, s2p4
7A – 7 valence electrons, s2p5
8A – 8 valence electrons, s2p6
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In case you’ve been
away or asleep?
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The Group 1A elements lose the s1 electron to
become +1 ion
Similarly,
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Group 2A: loses s2 to become a +2 ion
Group 3A: loses s2p1 to become a +3 ion
Group 5A: gains 3 electrons to become s2p6, and a -3 ion
Group 6A: gains 2 electrons to become s2p6, and a -2 ion
Group 7A: gains 1 electron to become s2p6, and a -1 ion
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Atoms will lose or gain electrons to
complete the OCTET of electrons
In other words, atoms will lose or gain
electrons to have filled valence s & p
orbitals, or the electron configuration of
the nearest noble gas.
Metals will lose electrons to become
CATIONS.
Nonmetals will gain electrons to
become ANIONS, not edible “anions”
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How do we represent the loss/gain of
electrons with the Lewis Dot
Structures?
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Remember, a Lewis Dot
structure is written as
follows.
Write the symbol.
Put one dot for each valence
electron
Don’t pair up until they have
to (Hund’s rule)
X
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Let’s Look at Atoms to Cations
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Metals lose electrons to attain noble
gas configuration.
If we look at the electron configuration,
it makes sense to lose electrons:
Ca 1s22s22p63s23p64s2 (2 valence e-s)
Ca2+ 1s22s22p63s23p6, a noble gas
configuration
Electron Dots For Cations
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Metals will have few valence electrons
(usually 3 or less)
These valence electrons are lost, creating
a positive-charged ion.
Ca
+2
Making a Pseudo-noble gas
configuration
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Electron Dots For Anions
What about Anions?
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Nonmetals gain electrons to attain
noble gas configuration, making
negative ions (anions)
S 1s22s22p63s23p4 has 6 valence e’s
S2- 1s22s22p63s23p6 a noble gas
configuration.
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Nonmetals will have many valence
electrons (usually 5 or more)
They will gain electrons to fill outer shell.
3-
P
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Now I Know You’re Wondering …
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Do Metals and Nonmetals “mate” to form a
compound?
Metals want to lose e, while nonmetals
want to gain e … a perfect match.
So how does this happen?
Ionic Bonding
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transfer of electrons.
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The bond is formed through the
Electrons are transferred to achieve
noble gas configuration.
The resulting anions and cations are
held together by opposite charges.
Ionic compounds are called salts.
Simplest ratio is called the formula unit.
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Ionic Bonding
The Metal:
Ca 1s22s22p63s23p64s2
Ionic Bonding
Ca2+
2
S-
Ca2+ 1s22s22p63s23p6
And the Non-metal:
S 1s22s22p63s23p4
This is the Lewis Dot
Structure of the Ionic
Compound
S2- 1s22s22p63s23p6
CaS
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+
Na Cl
The Lewis Dot Structure for
Sodium Chloride
NaCl
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Ionic Bonding
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Ionic Bonding
All the electrons must be accounted for!
Ca
P
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Ca
P
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Ionic Bonding
Ca2+
P
Ionic Bonding
Ca2+
P
Ca
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3
Ionic Bonding
Ca2+
P
Ionic Bonding
3-
Ca
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Ca2+
P
Ca
P
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Ionic Bonding
Ca2+
P
Ca2+
P
Ionic Bonding
3-
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Ca
Ca2+
P
Ca2+
P
3-
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Ionic Bonding
Ca
Ca2+
P
Ca2+
P
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3-
Ionic Bonding
3-
Ca2+
Ca2+
P
Ca2+
P
33-
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What Have we Learned?
Ionic Bonding
The Lewis Dot Structure for 3 Ca+2 & 2
P3-
3Ca2+ 2 P
Ca3P2
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3-
The Formula
Unit
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Is There an Easier Way to
Combine Ions?
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Write the Ionic Combinations & Lewis Dot
Structures of the Ionic Molecules for the
following combinations:
� Ba
+
Cl
� Al
+
O
�K
+
Br
+
N
� Li
The CRISS CROSS Method:
3+
Al
+
O
2-
Properties of Ionic Compounds
Crystalline structure, usually solids
� A regular repeating arrangement of
ions in the solid
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Al O
What would the Lewis
Dot Structure look like?
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Properties of Ionic Compounds
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Ions are strongly bonded together.
The Crystalline Structure is rigid, with longrange order.
Hardness & Density are related to crystal
composition and structure of the solid; i.e.
how much space is between the ions in the
“crystal lattice”
These structures tend to melt at Specific &
High melting points
Amorphous Solids are those molecules that
do not have an orderly arrangement.
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Do Ionic Solids Conduct?
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Conducting electricity is allowing charges
to move.
In a solid, the ions are locked in place.
Ionic solids are insulators.
When melted, the ions can move around.
Melted ionic compounds conduct.
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Dissolved in water they conduct (aqueous)
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NaCl: must get to about 800 ºC.
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Properties of Ionic Compounds
Bonding in Metals
What do Crystalline Solids look Like?
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OBJECTIVES:
Use the theory of metallic bonds to
explain the physical properties of
metals.
� Describe the arrangements of atoms in
some common metallic crystal
structures.
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Sea of Electrons
Metallic Bonding
How are atoms held together in a
metallic solid?
� Metals have low ionization energies,
and have a weak hold on their valence
electrons.
� These outer electrons easily move
around, as they do not "belong" to any
one atom, but are part of the whole
metal crystal.
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These outer electrons easily move around,
as they do not "belong" to any one atom,
but are part of the whole metal crystal.
The negatively charged electrons act as a
"cement" that hold the positively charged
metal ions in their relatively fixed positions.
+
+ + +
+ + + +
+ + + +
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Metals are Malleable
Malleable
Hammered into shape (bend).
� Also ductile - drawn into wires.
� Both malleability and ductility
explained in terms of the mobility of
the valence electrons
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+
+ + +
+ + + +
+ + + +
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Malleable
Ionic solids are brittle
+ + + +
+ + + +
+ + + +
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+
+
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Electrons allow atoms to slide by.
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+
+
+
+
-
+
+
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Alloys
Ionic solids are brittle
We use lots of metals every day,
but few are pure metals
� Alloys - mixtures of 2 or more
elements, at least 1 is a metal
� made by melting a mixture of the
ingredients, then cooling
� Brass: an alloy of Cu and Zn
� Bronze: Cu and Sn
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Strong Repulsion breaks crystal apart.
- + - +
+ - + - + - +
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Why use alloys?
Properties often superior to element
� Sterling silver (92.5% Ag, 7.5% Cu)
is harder and more durable than
pure Ag, but still soft enough to
make jewelry and tableware
� Steels are very important alloys
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corrosion resistant, ductility, hardness,
toughness, cost
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Some Common Alloys
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Steel: Contains 99.5% Fe and 0.5%
Carbon. Steel is much harder than Iron.
Stainless Steel: Ni & Cr is added to steel
to make it shiny, strong and corrosion
resistant.
Brass: An alloy that contains ~80% Cu
and 20% Zn. Brass is stronger and more
malleable than Cu.
Bronze: Contains 90% Cu and 10% Sn
(tin)
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Why use alloys?
Table 15.3, p.429 - common alloys
What are the types?
a) substitutional alloy- the atoms in the
components are about the same size
b) interstitial alloy- the atomic sizes
quite different; smaller atoms fit into
the spaces between larger
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