Chapter 8: Basic Concepts of
Chemical Bonding
• Why do TiCl4 and TiCl3
have different colors? ...
different chemical
properties? ... different
physical states?
Chemical Bonding and Properties
• Difference in colors is due to differences in
electronic configuration for TiCl3 and TiCl4
• Differences in chemical behavior are due to
differences in the types of bonds
• Bond: forces that hold atoms together in
molecules or ionic compounds.
Chemical Bonding
• Types of bonds and types of substances
– Ionic
– Covalent
– Metallic
• The type of bond between atoms is partially
responsible for the properties of the
substance.
Why do atoms form bonds?
Draw orbital diagrams for each of the following
elements
• Ne
• Na
• Cl
• H
• O
•
Lewis Symbols and the Octet
Rule
Lewis Symbols:
The number of
valence electrons
available for
bonding are
indicated by
unpaired dots.
Lewis Symbols
• These symbols are
called Lewis symbols.
• We generally place the
electrons on four sides
of a square around the
element symbol.
Why do atoms form bonds?
• Octet Rule
• Atoms tend to gain, lose, or share
electrons in order to acquire a full
set of valence electrons.
• Lewis Dot
Diagrams
• Used to illustrate an atoms valence
electrons
• Used to illustrate how electrons
rearrange during chemical reactions
Na
Xe
P
Lewis Dot Practice
•
•
•
•
•
•
•
O
Te
Ca
Ba
Ne
I
Cs
Ions and Ionic Compounds
• Ions are formed by adding or subtracting electrons from a
neutral atom or molecule.
• Cation: positive charge (remove electrons) Na+
• Anion: negative charge (add electrons)
• Ions may be monatomic or polyatomic
Cl-
03m07an1&2
Types of Ions
• Monatomic ions
– Single atom ions
• O 2• Na+
• Al3+
• Polyatomic ions
– More than one atom ions
• NH4 +
• OH –
• SO4 2-
Predicting Ionic Charges
• Electron Counts of Stable Ions
– Ions tend to have the same number of
electrons as the nearest noble gas.
• Main group ions of a given element tend to
be different by two units of charge.
• Transition metals are not as predictable, but
+2 and +3 are common.
ion_charges.exe
Main Group Elements
Note
periodicity
of charges
Transition Elements
• Not periodic; +2 and +3 common
B
C
BO33Borate
N
O
F
Charges
and
of
CO
NO Formulas
None
Carbonate
Nitrate
Known
NO
Oxoanions
3
2-
3
2
-
None
Known
-
Nitrite
• Oxoanions
generally
have the same
chargeClas
Si
P
S
4the simpleSiOanion
of the
PO43-same nonmetal.
SO42ClO34
Silicate
B
Related to
position in
the
periodic
Polyatomic Ions
table; note
exceptions
tend to reflect
forcharge
B, C, Nof the
the
base element
3-
BO3
Borate
C
Phosphate
2CO
3-3
POCarbonate
3
Phosphite
As Si 4SiO34
AsO
4
Silicate
Arsenate
AsO33Arsenite
N
O
F
Sulfate
Chlorate
NO3
None
None
2SO3
ClO
Nitrate
Known
Known
2
NO2Sulfite
Chlorite
Nitrite
P Se
S
Br Cl 32PO4
ClO-3
2- SO4
SeO
BrO
4
3
Phosphate
Sulfate
Chlorate
32PO3 Selenate SO3
ClO2Bromate
Phosphite
Chlorite
2- Sulfite
SeO
BrO
3
2
As
Se
Br
32AsO4Selenite SeO4
BrO3Bromite
Arsenate
Selenate
Bromate
32Te
I
AsO3
SeO3
BrO2Arsenite
TeO42- Selenite IO3Bromite
Te
I
Tellurate TeO42Iodate
IO3Iodate
TeO32- Tellurate
IO
2
TeO32IO2Tellurite Tellurite Iodite
Iodite
-
Why do atoms form bonds?
• Ionic bond
• A positively charged ion is
attracted to a negatively charged
ion.
• A transfer of electrons
• Metal and a Non-Metal
• Example
• NaCl
– Lewis Dot
diagram
Na
Cl
Na Cl
Why do atoms form bonds?
• Practice
• Mg, S
• Ca, Br
Metal
Non-Metal
Formation of an Ionic Compound
Vd02_007.mov
Properties of Ionic Bonds
• Ionic bonds are very strong, so separating ions
requires much energy
• High melting points, boiling points
• Crystals are hard and brittle
• Electrical insulators when solid, electrical
conductors when molten or dissolved in water
• Demo:
electric_pickle.mov
Electrical Conductivity
Solid NaCl
Liquid NaCl
03s11vd1
Structure and Properties
• Why are crystalline solids brittle,
whereas metallic solids are malleable?
Structure and Properties
Brittleness
brittle2.mov
maleable2.mov
Examples of Ionic Formulas
• What is the
formula of
each of these
compounds?
Writing Formulas for Ionic
Compounds
• Crisscross • Write the element symbols for the
Method
cation and anion, with the cation on
the left and the anion on the right.
• Example • Write each ion’s charge as a
superscript.
Ca and F
• Crisscross the two charges moving
them downward diagonally from one
superscript to the other subscript.
Writing Formulas for Ionic
Compounds
• Practice
• Li and O
• Mg and O
• Ca and N
Chemical Formulas
• Remember
• Combine ions to obtain electrical neutrality
Ionic_Formula.exe
Naming Binary Ionic Fixed Charge
Compounds
(Formula  Name)
Formula  Name
1. Name the cation
2. Name the anion, changing the
ending to ide
Example:
Li2O
Lithium Oxygen + ide
Lithium Oxide
Naming Binary Ionic Compounds
Name  Formula
Example:
Calcium Chloride
Ca +2 and Cl -1
CaCl2
1. Identify the ions involved
2. List the cation first and then
the anion
3. Determine that charge of each
ion involved
4. Balance the charges so the
compound is neutral.
Naming Binary Ionic Compounds
STOCK (Transitional Metals)
Formula  Name
1. Name the cation
2. Determine the charge of the
anion
3. Based on the anion, what
charge does the cation need to
make the compound neutral.
CoCl2
4. Write the cation charge in
Example:
parenthesis as a roman
Cobalt II chloride
numeral
5. Name the anion.
Naming Binary Ionic Compounds
Stock (Name  Formula)
Name  Formula
1.
2.
Example:
Calcium Chloride
Copper(II) Oxide
3.
4.
List the cation first and then the
anion
Give the cation the charge stated in
the name (roman numeral)
Determine the charge of the anion
Balance the charges so the
compound is neutral.
Ca +2 and Cl –1 CaCl2
Cu + 2 and O –2 CuO
Naming Ternary Molecular
Structures
What is a Ternary •A molecule that has more than
Molecular
two elements.
Structure?
•A combination of a metal and
a polyatomic ion.
Example
•Same rules as Binary
Ionic/Stock but just name the
•MgSO4
Magnesium Sulfate polyatomic
•CuSO4 Copper (II)
Sulfate
Compounds
• How do we distinguish between ionic and
covalent compounds?
• What do you notice?
Why do atoms form bonds?
• Covalent
bond
• Shared pair of electrons between
two atoms.
• Non-metal and Non-metal
Lewis Structures
• Lewis Structures
• Lewis Dot Examples
A representation of a molecule that shows
how the valence electrons are arranged among
the atoms in the molecule
* G. N. Lewis
Why do atoms form bonds?
• Molecule
• Diatomic
Molecules
• Super 7
• A group of atoms united by a
covalent bond
• A few elements only exist as a
pair of atoms never as a single
lone atom
• Cl2, I2, F2, Br2, O2, H2, N2
Why do atoms form bonds?
• Characteristics • Can form multiple bonds satisfy the
octet rule
of covalent
bonds
• Single Bonds • Two atoms share exactly one pair of
electrons.
– Ex. H2
• Double Bonds • Two pairs of electrons shared between
two atoms.
– Ex. O2, H2CO
• Three pairs of electrons are shared
• Triple Bonds
between atoms
– Ex. N2, C2H2
Properties of Covalent Bonds
•
•
•
•
Solids are usually soft
low melting points
low boiling points
Properties arise because molecules are
not strongly held together
• Usually found with nonmetals
Structural Formulas
• Specifies which atoms are bonded
• Why do
to each other
atoms form
• Distinguish the difference between
bonds?
substances with the same
molecular formula
Structural Formulas
Examples
• See models of different types: Why do we have
different types of models?
Structural Formulas
• A few Models
NH3
CO2
• How are the atoms connected?
H2SO4
Lewis Structure for Super 7’s
• Draw Lewis structures for super 7’s
Chemical Formulas
• S8, O2, O3 - What formulas do we find for
elements? Elements with different formulas are
called allotropes.
• How many atoms make a molecule? Is there any
pattern?
xenon
oxygen
phosphorus
sulfur
ozone
Naming Binary Covalent
Compounds
Covalent compound •
Definition
•
Non-metal and non-metal
Share Electrons
Naming Binary Covalent
Compounds
Prefixes
1= mono
2= di
3 = tri
4 = tetra
5 = penta
6 = hexa
7 = hepta
8 = octa
9 = nona
10 = deca
Naming Binary Covalent
Compounds
Practice
Name  Formula
What is the formula for
the following
compounds?
1.
Write the chemical formula of the
first element listed.
2. Write the prefix number as a
subscript.
3. Write the chemical formula of the
second element listed.
4. Write the prefix number as a
subscript.
a. Pentachlorine dioxide
b. Carbon monoxide
c. Tribromine hexasulfide
Naming Binary Covalent
Compounds
Practice
FormulaName
1.
2.
What is the name of the
following
compounds?
a.
b.
c.
Write the number of the first
element as a prefix, add the name
of chemical.
Write the number of the second
element as a prefix, add the name
of chemical and end in –ide.
P4C8
F9I6
SN3