Ionic
Compounds
and
Ionic Bonding
Chemical Bonds
There are three basic types of bonds:
Ionic - The electrostatic attraction between ions
Covalent - The sharing of electrons between atoms
Metallic - Each metal atom bonds to other metals
atoms within a "sea" of electrons (covered in a later unit)
Periodic Table - Review
The periodic table is "periodic" because of certain trends that are seen in the elements.
Properties of elements are functions of their atomic number.
Elements from the same family/group have similar physical and chemical properties.
Atoms are listed on the periodic table in rows, based on number of protons, which is
equal to the number of electrons in a neutral atom.
The Periodic Table of the Elements
The periodic table can be also divided into metals (left/blue) and nonmetals
(right/yellow).
A few elements retain some of the properties of metals and nonmetals, they are called
metalloids (staircase/pink).
B
Si
Ge
As
Sb Te
?
1
In the periodic table, the elements are arranged in __________.
A
alphabetical order
B
order of increasing atomic number
C
order of increasing metallic properties
D
order of increasing neutron content
E
reverse alphabetical order
F
I don't know how to answer this.
Elements __________ exhibit similar physical and chemical properties.
2
A
with similar chemical symbols
B
with similar atomic masses
C
in the same period of the periodic table
D
on opposite sides of the periodic table
E
in the same group of the periodic table
F
I don't know how to answer this.
3
Which pair of elements would you expect to exhibit the greatest
similarity in their physical and chemical properties?
A
H, Li
B
Cs, Ba
C
Ca, Si
D
Ga, Ge
E
C, O
F
I don't know how to answer this.
4
Which one of the following is a nonmetal?
A
W
B
Sr
C
Os
D
Ir
E
S
F
I don't know how to answer this.
5
Potassium is a __________ and chlorine is a __________.
A
metal, nonmetal
B
metal, metal
C
metal, metalloid
D
metalloid, nonmetal
E
nonmetal, metal
F
I don't know how to answer this.
Review: Octet Rule
Atoms tend towards having complete outer shells of electrons (remember
stability).
A full outer shell will have:
2 electrons in the s subshell and
6 electrons in the p subshell ( s2p6 configuration)
Octet rule: atoms tend towards having a total of 8 electrons
8 valence electrons make an octet
Valence Electrons
Valence electrons are the electrons in the highest occupied
energy level of an element’s atoms.
The number of valence electrons largely determines the
chemical properties of an element.
Valence
electron
To find the number of valence electrons in an atom of a representative element,
simply look at its group number.
Atoms in group 3 have 3 valence electrons,
atoms in group 17 have 7 valence electrons, etc.
Valence Electrons
1 2
Number of valence electrons in
neutral atoms:
3 4
5
6
7 8
1-4
There is one exception:
helium has only 2 valence electrons.
6
How many valence electrons does Aluminum have?
A
5
B
7
C
3
D
27
E
I don't know how to answer this.
7
How many valence electrons does Barium have?
A
1
B
2
C
52
D
3
E
I don't know how to answer this.
Ions
Cations are positive and are formed by
elements on the left side of the
periodic chart (metals).
Anions are negative and are formed
by elements on the right side of the
periodic chart (nonmetals).
The Formation of Cations
Metals usually give up valence electrons
This results in a noble gas (8 electron) outer shell.
Na : 1s2 2s2 2p6 3s1
Na+1 : 1s2 2s2 2p6
Ne atom
Loss of valence
electrons
The configuration of the Sodium ion is the same as Neon
The Formation of Cations
Na atom
Na+ ion
loses e-
11p
11e-
11p
10e-
The Formation of Cations
Cations of Group 1A elements always have a charge
of 1+.
Cations of Group 2A elements always have a charge
of 2+.
Mg
Magnesium atom
(electrically
neutral,
charge = 0)
Mg2+
Magnesium ion
(+2 indicates 2 units of
positive charge)
+
2e-
(2 in front of e- indicates 2
units of negative charge)
The Formation of Anions
Nonmetals usually gain valence electrons.
This results in a noble gas (8 electrons) outer shell
Cl: 1s2 2s2 2p6 3s2 3p5
Cl- 1s2, 2s2, 2p6, 3s2, 3p6
A chloride ion has the same electron configuration as argon.
Ar atom
The Formation of Anions
Cl- ion
Cl atom
Gains an e17P
17e-
17p
18e-
The Formation of Anions
Anions of Group 15 (5A) elements have a
charge of 3-
Anions of Group 16 (6A) elements always have
a charge of 2-
Anions of Group 17 (7A) elements have a
charge of 1-
8
Metals tend to __________ electrons and cations tend to
__________ electrons.
A
gain, gain
B
lose, lose
C
gain, lose
D
lose, gain
E
neither, they keep their electrons
F
I don't know how to answer this.
Anions tend to be __________ and cations tend to be __________.
9
A
metals, metals
B
nonmetals, nonmetals
C
metals, nonmetals
D
nonmetals, metals
E
metalloids, metalloids
F
I don't know how to answer this.
10
Metals lose electrons to form cations
True
False
11
Anions are formed from nonmetals
True
False
12
Nonmetals tend to lose electrons forming ions
True
False
13
This is the ion formed from a calcium atom
A
Ca+
B
Ca2+
C
Ca-
D
Ca2-
E
I don't know how to answer this.
14
Barium forms an ion with a charge of __________.
A
1+
B
2-
C
3+
D
3-
E
2+
F
I don't know how to answer this.
15
Aluminum forms an ion with a charge of __________.
A
2+
B
1-
C
3+
D
2-
E
0
F
I don't know how to answer this.
16
Of the following, __________ contains the greatest number of
electrons.
A
P3+
B
P
C
P2-
D
P3-
E
P2+
F
I don't know how to answer this.
17
Oxygen forms an ion with a charge of __________.
A
2-
B
2+
C
3-
D
3+
E
6+
F
I don't know how to answer this.
18
Iodine forms an ion with a charge of __________.
A
7-
B
1+
C
2-
D
2+
E
1-
F
I don't know how to answer this.
19
This is the ion formed from nitrogen
A
N-
B
N2-
C
N3+
D
N3-
E
I don't know how to answer this.
20
Predict the charge of the most stable ion of S?
A
3+
B
1-
C
6+
D
2+
E
2-
F
I don't know how to answer this.
Ionic Bonding
Electronegativity is how strongly an atom attracts electrons.
Atoms with a high electronegativity will be able to attract electrons away from atoms
with a much lower electronegativity.
This removal of electrons can occur when the difference in electronegativity between
the two atoms is approximately 1.7 or higher.
Once a positive and negative ion are formed, they will be attracted to each other via
the electrostatic force:
F = k q1 q2
r2
Note: The heavier nonmetals from 4,6,5th
groups
( In, Tl, Sn, Pb, Sb Bi )
may act like metals
Ionic Bonding
An electronegativity difference of approximately 1.7 can
only occur between a metal and a nonmetal.
Which pair of atoms will form an ionic bond?
21
A
Li and Ne
B
K and Br
C
K and Cs
D
S and Cl
E
I don't know how to
answer this.
Which pair of atoms will form an ionic bond?
22
A
Li and Be
B
Na and Mg
C
K and Ca
D
Na and Cl
E
I don't know how to
answer this.
23
Which of the following compounds would you expect to be ionic?
A
H2O
B
CO2
C
SrCl2
D
SO2
E
H2S
F
I don't know how to answer this.
Formation of Ionic Compounds
Compounds composed of cations and anions are called ionic compounds.
Although they are composed of ions, ionic compounds are electrically neutral.
The electrostatic forces that hold ions together in ionic compounds are called
ionic bonds.
Ionic Bonds
When sodium and chlorine are close together, sodium's valence electron flies off and "harpoons" the
chlorine atom.
The result is a sodium cation (+) next to a chloride anion (-)
These oppositely charged two ions attract: they reel one another together to form an ionic bond.
Na
1s2 2s2 2s2 2p6 3s1
Cl
1s2 2s2 2p6 3s2 3p5
Na+
1s2 2s2 2p6
Cl-
1s2 2s2 2p6 3s2 3p6
1s2 2s2 2p6
Ne
1s2 2s2 2p6 3s2 3p6
Ar
Ionic Bonds
The electron transfer process in creating an ionic bond:
Na
Cl
The dots represents the valence electrons in an atom.
click here for an animation of this
reaction
Formula Units
A chemical formula shows the kinds and
numbers of atoms in the smallest
representative unit of a substance.
A formula unit is the lowest whole-number
ratio of ions in an ionic compound.
Every ionic compound has a 3D array of
positive and negative ions.
[*]
Properties of Ionic Compounds
They are crystalline solids at room temperature
They have high melting points
They conduct electricity when melted (molten) or dissolved in water
(aqueous)
Ionic bond
Nomenclature
Writing ionic compounds
or
Criss-Cross Rule
1. Main Group metals
Alkali (1)
Alkali earth (2)
Group 13 (3A)
Criss-Cross Rule
Aluminum
Chloride
Example: Aluminum
Chloride
Step 1:
write symbols & charge of elements on top
(charges based on group numbers)
Step 2:
criss-cross charges as subscripts
Step 3:
combine as formula unit
(“1” is never shown)
Al
3+
Al 1
AlCl
Cl
Cl
3
1-
3
Criss-Cross Rule
Example: Aluminum Chloride
Step 1:
Aluminum
Chloride
Step 2:
3+
Al
1Cl
Step 3:
Al
1
Cl
AlCl
3
3
Criss-Cross Rule
Example: Aluminum Oxide
Step 1:
Aluminum
Oxide
Step 2:
3+
Al
2O
Step 3:
Al
O
2
Al2O3
3
2. Transitional metals
Silver
Iron II
Zinc
Criss-Cross Rule
Chromium (IV) Chloride
Step 1:Example:
write symbols & charge of elements on top
(charges given by name)
Step 2:
criss-cross charges as subscripts
Step 3:
combine as formula unit
(“1” is never shown)
Chromium Chloride
Al
4+
Al 1
CrCl
Cl
Cl
4
1-
4
Transitional metals exception
Ag = +1
Zn = +2
Steps in Naming
1. Determine if its ionic
2. Is it a main group metal or transition
–
Does it have a metal in it
Steps in Naming
1. Determine if its ionic
Does it have a metal in it
2. Is it a main group metal or transition
(Ionic) Compounds
2 types of ionic compounds
All
have
metals
in
them
Main group – 1A, , 2A, 3 - 13A
Transitional - 3B -12B
Naming Ionic Compounds
Main group metals.
To name these compounds, give the name of metal followed by the
name of the non-metal, with the ending replaced by the suffix –ide.
Examples:
NaCl
sodium chloride
(Na1+ Cl1-)
CaS
calcium sulfide
(Ca2+ S2-)
AlI3
aluminum iodide
(Al3+
I1-)
Ionic Compounds II
Containing a transition Metal
1. Give the name of the metal followed by
Roman numerals in parentheses to indicate
the oxidation number or charge
2. Give the name of the nonmetal, with its
ending replaced by the suffix –ide.
Examples
• Fe (II) Oxide
• Sn (IV) Oxide
The roman numeral is based on the charge of a single
metal atom!
Procedures to write their names
1.
2.
3.
4.
5.
6.
Write the symbols for cation and anion
Find the total charge for the anion, write
it on top of the anion (charge X # of
atoms)
Write the opposite charge on top of cation
Show the number of atoms for cation
Calculate the charge each metalic cation
should have.
Write the metal with correct roman
numeral based on a single cation and the
anion
Example = Cr2O3
Step 1 Write the symbol for the
elements and number of atoms for
cation and anion
Cr
2
O
3
Example = Cr2O3
Step 2 :Find the total charge for the anion
a. Multiply charge on a single ion by its subscript
A single O anion
has a -2 charge it
has 3 atoms so
total charge is -6
O
-2
-2
-2
- 6
- 6
3
Example = Cr2O3
Step 3
Write the opposite charge on top of
cation
• Cr2
+6
O3-6
-2
-2
-2
Example = Cr2O3
Step 4 Show the number of atoms for cation
•
+6
Cr2
-6
O3
-2
-2
-2
- 6
Example = Cr2O3
Step 5 Calculate the charge each metallic cation
should have
•
+6
Cr2
O3
+3
-2
+3
-2
+6
-2
- 6
-6
Example = Cr2O3
Step 6
Write the metal with correct roman
numeral based on a single cation and the anion
• Cr+2 6
O3
+3
-2
+3
-2
-2
Based on a single atom
-6
Answer = chromium (III) oxide
Examples: Transition metals
Formula
1
2
3
4
Hg2O
HgO
Fe2O3
FeO
Name
31
The formula for barium sulfide is Ba2S2.
True
False
Polyatomic Ions
or Ternary Ionic Compounds
Gang Up and Charge
Polyatomic Ions
• Charged particles made of more than one kind of
atom.
• Atoms are held together with covalent bonds.
• Each has its own name, based on the atoms it
contains. Many chemists memorize these names.
We will use a list.
Cyanide Ion
CN-
Common Polyatomic Ions
Names of Common Polyatomic Ions
Ion
NH4 1+
NO2 1NO3 1widely
SO3 2SO4 2HSO4 1OH 1CN 1PO4 3HPO4 2H2PO4 1-
Name
ammonium
nitrite
nitrate
sulfite
sulfate
hydrogen sulfate
(“bisulfate” is a widely
used common name)
hydroxide
cyanide
phosphate
hydrogen phosphate
dihydrogen phosphate
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 100
Ion
CO3 2-
ClO 1ClO2 1ClO3 1ClO4 1C2H3O2 2MnO4 1Cr2O7 2CrO4 2O2 2-
Name
carbonate
HCO3 1hydrogen carbonate
(“bicarbonate” is a
used common name)
hypochlorite
chlorite
chlorate
perchlorate
acetate
permanganate
dichromate
chromate
peroxide
CO3-2
carbonate
This ion is composed of one carbon and three oxygens and the
entire group has a charge of -2.
Polyatomic ion – Group of atoms that act as a unit and carry a charge.
More examples:
SO4
-2
SO3
-2
ClO4
-1
ClO3-1
Sulfate
Sulfite
Perchlorate
PO4-3
Phosphate
C2H3O2-1
Acetate
OH-1
Hydroxide
NO3-1
Nitrate
NO2-1
Nitrite
Chlorate
NH4+1
ClO2-1
Chlorite
ClO-1
Hypochlorite
Ammonium
(only positive PI)
You need to learn these!!!
How do you recognize Ternary Ionic Compounds?
Composed of two ions in which at least one is a
polyatomic ion.
There is only one positive polyatomic ion (NH4+1)
Three possible types of Ternary Ionic Compounds:
•Ammonium + negative ion (nonmetal)
•Metal (positive ion) + negative polyatomic
s ion
•Ammonium + negative polyatomic ion
How do you name Ternary Ionic Compounds?
EASY! PIECE OF CAKE! NO PROBLEM!
Name the first ion.
Name the second ion. Isn’t that simple??!!
Examples:
Na2CO3
Sodium
carbonate
Notice that you do
NOT change the suffix
– just name the
polyatomic ion
When you look at this compound you should
recognize that this is NOT binary. There are
THREE elements present. When you see this,
immediately look for a polyatomic ion.
Carbonate is present here.
Name the first ion.
Name the second ion.
How do you write formulas for Ternary Ionic
Compounds?
Very much like writing formulas for Binary Ionic
Compounds.
Two steps:
•Write the formulas/symbols of each ion.
•Balance the charges by supplying subscripts.
•If a subscript is needed for a polyatomic ion, it
must be put in parentheses with the subscript
on the outside.
Let’s do some!!
Magnesium Phosphate
Step 1:
Magnesium
Step 2:
2+
Mg
Step 3:
Mg
Step 4:
3
Phosphate
3PO4
(PO4)
Mg3(PO4)2
2
polyatomic Compounds
Ca3(PO4) 2
1. ________________
calcium phosphate
(NH4)2CO3
2. ________________
ammonium carbonate
3. ________________
Al2(SO4)3
aluminum sulfate
4.
Na2SO4
____________________
sodium sulfate
5.
LiCN
____________________
lithium cyanide
6.
Ba(ClO3)2
7. ________________
Cu(OH)2
____________________
barium chlorate
copper (II) hydroxide
43
The formula for sodium hydroxide is
A
Na (OH)2
B
Na(OH)
C
Na(OH2)
D
Na(HO)
E
I don't know how to answer this.
44
The formula for aluminum phosphate is:
A
Al(PO4 )
B
Al3(PO4)
C
Al2(PO4)3
D
Al3(PO4)3
E
I don't know how to answer this.
47
NaClO is
A
sodium chlorate
B
sodium chloride
C
D
sodium chlorite
E
sodium hypochlorite
I don't know how to answer this.
49
Ammonium carbonate is
A
(NH4)(CO3)
B
(NH4)2(CO3)
C
(NH4)(CO3)2
D
E
(NH4)2(CO2)
I don't know how to answer this.
PRACTICE
Writing Formulas for Ionic Compounds
Complete the table by filling in the formula for the ionic compound formed by each pair of
cations and anions, as shown for the first pair.
PRACTICE
Writing Formulas for Ionic Compounds
Write the formula for the following compounds:
1. Magnesium iodide
2. Calcium sulfite
3. Barium hydrogen carbonate
4. Iron (III) phosphate