HONORS CHEMISTRY
Oct 30, 2013
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.
Notes handout
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
•
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 (refer to back of P. table)
– 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
ion_charges.exe
as the nearest noble gas.
• Transition metals are not as predictable, but +2
and +3 are common.
– 3 transition metals with fixed charge (Ag+1, Zn+2 Cd+2)
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
chargeCl as
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
-
Practice on Ionic Charges
• Pair Share: What is the common charge of
an ion of potassium, K?
• Pair Share: What is the common charge of
an ion of sulfur, S?
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
Draw Lewis Dot Structure!!!
Metal
Non-Metal
What holds Ionic bonds together?
• Electrostatic Attraction
• + and - charge
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
• Mg and C
Practice
• Rewrite these incomplete formulas as
correct formulas.
AlS
CaP
BaBr
• Make formulas from the following ions:
Mg2+,
OH-
Fe2+, PO43-
Sc3+, O2-
Bonding with a partner
• You will receive a card with an ion.
• You will find another person with the
opposite charge from you.
• You will write the ions on your paper and
the formula they will create together.
• Exchange cards and repeat the steps again
until you fill up your paper.
Chemical Formulas
• Remember
• Combine ions to obtain electrical neutrality
Ionic_Formula.exe
STOP
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
More examples:
NaCl
CaS
AlF3
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 (crisscross method).
Practice
Write the structural formula for the following:
Hint: separate them into ions and then criss cross
Magnesium phosphide
Calcium iodide
Beryllium oxide
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.
Examples
• Fe3P2
• Cu2S
• NiO
Naming Binary Ionic Compounds
Stock (Name  Formula)
Name  Formula
Example:
Calcium Chloride
Copper(II) Oxide
1. List the cation first and then
the anion
2. Give the cation the charge
stated in the name
3. Determine the charge of the
anion
4. Balance the charges so the
compound is neutral.
Ca +2 and Cl –1 CaCl2
Cu + 2 and O –2 CuO
Examples
• Copper (II) nitride
• Vanadium (II) oxide
• Zinc chloride
• 3 Special Transition
Metals (do not require
Roman numerals:
fixed charge):
– Zn
– Cd
– Ag
Practice
• Writing Formulas “Transition Metals (stock
Method)” wksheet
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
Rally Table
•
•
•
•
NaF
K2CO3
MgCl2
Be(OH)2
Practice Worksheet
• Refer to “Naming Ionic Compounds
Practice Worksheet”
• Make Flash Cards: Polyatomic Ions
Start 11/5/12
Brain Teaser (11/5/12)
• Write the formula and draw the Lewis Dot
structure: Potassium and Phosphorus
• Name or Write the formula of the
following compounds:
–
–
–
–
SrS
Cu2S
Iron (II) oxide
Magnesium cyanide
Agenda (11/5)
•
•
•
•
•
•
•
•
Brain Teaser
Collect Progress Report
Grade Practice Ionic Bonding Quiz and WS
Questions?
Ionic Review Questions
Ionic Bonding Quiz
Notes: Covalent Bond
Homework
– Study Ionic Compounds Worksheet
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
Round Table – Covalent Bonding
•
•
•
•
•
•
SiH4
NH41+
H2Se
HCl
HF
*SO42-
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
bonds?
between 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
Brain Teaser
• Write the Lewis structure for each of the
following simple molecules.
• H2S
• C2H4
• SiF4
Shapes Lab
• Work with a partner
• Draw the Lewis Dot Diagrams for each of
the compounds
• Build each of the compounds using the
model kits.
• Sketch the shape of the model
– Remember all the holes (bonding sites) of each
atom must be filled in order for it to satisfy the
octet rule.
Shapes of Molecules
VSEPR
Theory
• Valence Shell Electron Pair Repulsion
• System for predicting molecular shape
based on the idea that pairs of electrons
orient themselves as far apart as
possible.
Shapes of Molecules
How to use VSEPR theory
• Total Electron Pairs
Examples
• HBr
– # of Shared and unshared
pairs
• Shared Electron Pairs
– # of Pairs involved in
covalent bonding
• Unshared electron Pairs
• H2O
– # of Lone pairs of electron
• Shape or Geometry
– Linear, bent, trigonal
planar, tetrahedral
• PH3
Shapes of Molecules
What do we do with
multiple bonds?
Examples
• N2
• HCN
Count the sides of the
• H2CO
central atom that have
bonds on them
Practice
• Shapes of molecules
THE PASS IT GAME!!
• You will have one paper for each row.
• Your job is to do one section and then pass it to
the next person.
• There are three sections: Electron dot, molecular
drawing and VSEPR name & angle
• Once the last person is done raise your hand and
get a stamp if all is correct.
• 1st team will get a prize for each Pass it game!
CCl4
SeO3
BeF2
Polarity of Molecules
Electronegativity
Polar Covalent
Bonds
Polar Molecule
– Ex. H2O
• Ability to attract electrons
• Difference in electronegativity tells us
who wants the electrons more.
• Atoms do not share electrons evenly.
• Atoms with greater electronegativity
have a slight negative charge.
• A molecule is polar if the charge is
not evenly distributed
Polarity of Molecules
What would make • If the 2 atoms have similar
a Non-Polar
electronegativities.
Covalent Bond?
• The atoms involved exert similar
pull on the electrons.
– Examples
• F2
• PH3
Bond Types and Elctronegativity
Electronegativity
Difference
< 0.4
Bond Type
Non- polar covalent
Between 0.5 and 1.9
Polar covalent
> 2.0
Ionic
Polarity of Molecules
• Other side of shapes
• Draw each molecule in its correct VSEPR
shape.
Ionic
Properties
vs.
Covalent
Rally Table - Types of chemical bonds