CHEMISTRY
October 19th, 2011
Welcome Back!
October 19th, 2011
•
Brainteaser:
– Let’s reflect on last quarter’s performance:
1. What are some things you thought you did
well for this class?
2. What are some things you think you could
improve for this quarter?
3. What is your overall goal for this quarter (i.e.
what do you want to accomplish this quarter
and how are you going to do it?)
Agenda
• Brainteaser
• Unit 5: Ionic Bonding Notes
• Homework
– Ionic Bonding Practice Worksheet
Unit 4: Chemical Bonding
• Bonding
– 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.
Chemical Bonding
• Bonding
– Involves the valence electrons or outermost shell (or
highest shell) electrons
– For group A elements – the group number tells how
many valence electrons
• For example:
– K, Ca, C, B, N, F, Ne
– Lewis Dot Structures show the valence electrons
around an atom and for most molecules and
compounds a complete octet for the elements is
needed.
• For example: N, Al, H2O
Lewis Dot Structures
• These symbols are
called Lewis symbols 
• We generally place the
electrons on four sides
of a square around the
element symbol.
Drawing Lewis Dot Structure
• Place DOTS around the SYMBOL
clockwise pairing up dots on the second
time around
– For example:
• Magnesium (Mg) and Oxygen (O)  MgO
Mg
O
Ionic Bonding
Ions and Ionic Compounds
• Ions are formed by adding or subtracting
electrons from a neutral atom or molecule.
• Cation: positively charged ions (remove e-)
• Anions: negatively charged ions (add e-)
Two Types of Ions
• Monatomic ions
– Single atom ions
• O 2• Na+
• Al3+
• Polyatomic ions
– More than one atom ions
• NH4 +
• OH –
• SO4 2-
Predicting Charges of Ions
• Electron Counts of Stable Ions
– Ions tend to have the same number of
electrons as the nearest noble gas.
• Transition metals are not as predictable, but +2
and +3 are common.
Main Group Elements
Note
periodicity
of charges
Transition Elements
• Not periodic; +2 and +3 common
B
BO33Borate
Charges
and
Formulas
of
C
N
O
F
CO
NO
None
None
Carbonate Oxoanions
Nitrate
Known
Known
3
2-
3
-
NO2Nitrite
• Oxoanions
generally
have the
Si
P
S same Cl
42charge as
simple
sameClO3SiOthe
PO43-anion ofSOthe
4
4
C
N
O
F
Silicate B BO Phosphate
Sulfate
Chlorate
nonmetal.
CO
NO
None
None
32POCarbonate
SO3
ClO
Related to
Borate
Nitrate
Known
Known
3
2
NO
Phosphite
Sulfite
Chlorite
Nitrite
position in
P Se
S
As Si
Br Cl
SiO3PO
ClO2- SO
AsO
SeO
BrO
the
periodic
4
4
3
Silicate
Phosphate
Sulfate
Chlorate
Polyatomic Ions
PO Selenate SO
ClO
Arsenate
Bromate
table; note
Phosphite
Chlorite
2- Sulfite
AsO33SeO
BrO
3
2
As
Se
Br
AsO Selenite SeO
BrO
Arsenite
Bromite
exceptions
Arsenate
Selenate
Bromate
tend to reflect
Te
I
AsO
SeO
BrO
for
B,
C,
N
2Arsenite
TeO4 Selenite IO3Bromite
the charge of the
3
3-
3
2-
3
2
4
4-
4
3
-
-
3-
4
3-
4
3
3
3-
3-
3
2-
4
3
Te
base element
2-
2
2-
-
3
2-
Tellurate TeO42TeO32- Tellurate
TeO32Tellurite Tellurite
-
2
I
-
-
Iodate
IO3IO2Iodate
IO2Iodite
Iodite
Ionic Bonds form when…
• A cation (metal) bonds with an anion
(nonmetal)
• A salt is formed:
– For example: Sodium: Na “metal” bonded to
Chlorine: Cl “nonmetal”
– For example: Magnesium: Mg “metal” bonded
to Chlorine: Cl “nonmetal”
Ionic Bonding:
The Formation of Sodium Chloride
 Sodium has 1 valence electron
 Chlorine has 7 valence electrons
 An electron transferred gives
each an octet
Na: 1s22s22p63s1
Cl: 1s22s22p63s23p5
Ionic Bonding:
The Formation of Sodium Chloride
This transfer forms ions, each
with an octet:
Na+ 1s22s22p6
Cl- 1s22s22p63s23p6
The resulting ions come together
due to electrostatic attraction
(opposites attract):
Na+ ClThe net charge on the compound
must equal zero
Lewis Dot Drawing
• 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
Practice
• Draw the Lewis dot structures for the
following compounds:
– CaO
– BaCl2
– Na2S
Writing Formulas for Ionic
Compounds
• Crisscross
Method
• Example:
Ca and F
• Write the element symbols for the
cation and anion, with the cation on
the left and the anion on the right.
• Write each ion’s charge as a
superscript.
• Crisscross the two charges moving
them downward diagonally from
one superscript to the other
subscript.
Practice
• Write the correct formula for the ionic
compounds composed of the following
pairs of ions using the crisscross method:
– Potassium and iodide
– Magnesium and chloride
– Aluminum and bromide
– Cesium and nitride
– Barium and sulfide
– Iron (II) and fluoride
CHEMISTRY
October 20th, 2011
Warm Up
• Write the correct formula for these ionic
compounds:
– Aluminum oxide
– Barium nitride
– Iron (III) oxide
– Magnesium carbide
Agenda
• Brainteaser
• Grade Homework: Practice W/S
• Unit 5 Notes:
– Naming Ionic Compounds
– Properties of Ionic Compounds
• Partner Bonding Activity
• Homework:
– Naming Ionic bonds W/S
Naming Ionic Compounds
• Step 1:
– Cation is written first in the name; anion is written second in the
name
• Name of cation is the same as the neutral atom element
(Na+ = Sodium)
• Step 2:
– Anion is written by adding the suffix –ide to the root of the
element name (I- = iodide)
• For example: NaCl = Sodium Chloride, Al2O3 = Aluminum oxide
• Step 3:
– Figure out if you need a Roman numeral in the name (transition
metals).
• Figure out what the Roman numeral should be
– For example: Fe2O3
• Step Four: Check your work
Practice
Naming Ionic Compounds
•
•
•
•
•
KF
AlF3
KCl
Na3P
Fe2O3
Properties of Ionic Bonding
• Definition:
– In an ionic bond, a positively charged ion is
attracted to a negatively charged ion
• Electrostatic Attraction
Properties of Ionic Bonding
• Solid at room temperature
• Electrical conductivity
– Conducts electricity when dissolved in water or in liquid
(molten) form
– Dissociated ions can carry charge through the solution
• Hardness
– Hard but brittle
– Electrostatic repulsion
• Melting points and Boiling points
– High melting and boiling point
– Forces of attraction between positive and negative ions
are strong
Properties of Ionic Bonding
Quiz
• Write the chemical formula for these ionic
compounds:
– Sodium bromide
– Potassium nitride
– Beryllium phosphide
• Write the chemical names for these ionic
compounds
– SrCl2
– MgI2
– Ba3N2