The Octet Rule
Ionic Compounds
are formed from a metallic cation, and a non-metallic anion
Ionic Bonding
Anions and cations are held together by opposite charges.
Ionic compounds are called salts.
The bond is formed through the transfer of electrons.
Electrons are transferred to achieve a noble gas configuration.
(very stable)
. .......Na+Cl
Na+ + .......Cl. -Example 1
Na has 1 valence electron because it is in Group 1Cl has 7
valence electrons because it is in Group 17
Example 1
Na+Cl -
Na gives his one valence electron to Cl. Now both atoms are
happy. They each have a stable set-up of electrons like noble
gases. How many do they need in their valence shell to be
stable?
Ionic Bonding
All the electrons must be accounted for!
Ca
P
Ionic Bonding
Ca
P
Sometimes atoms cant satisfy each other in a one to one
ratio
Making Formulas
Ca+2
P
Notice Ca is happy but P still needs one more electron. So watch
what happens.
Ca+2
P
Ca
Making Formulas
Ca+2
P -3
Ca
But what about the 2nd Ca?Making Formulas
Ca+2
P-3
Ca
P
Making Formulas
Ca+2
P -3
Ca+2
P
OK, 2nd Ca is Happy but 2nd P is not now!Making Formulas
Ca+2Ca+2Ca
Making Formulas
P -3
P
Ca+2Ca+2Ca+2Finally everyones happy!Making Formulas
P -3
P -3
Ca3P2So whats the formula for this Compound?Making Formulas
Now complete your Ionic Formulas Worksheet.
Steps to remember1)Get charges for the cation and anion.(Look at
the Periodic Table) Cation always comes first!2)Put polyatomics in
parenthesis.3)Balance the charges so that they add up to zero by
using subscripts. (Cross method)
Writing Formulas: The Cross-Out Method
Steps to Remember:
1) Get charges for the cation and anion. Cation always comes
first!
2)Balance the charges so that they add up to zero by using
subscripts. (cross-out method)
Reminder: Get charges from the Periodic Table
+2+1+3-3
-2-1
Cation?Anion?Ba+2Br-1
BaBr2(The one is understood)Example: Ba and Br
Now complete your ionic cross-out worksheet.
Polyatomic Ions
Groups of atoms that stay together and have a charge.
Found on p. 7 of your Chemistry Reference Tables
NameChargeFormula
How Do We Use Polyatomic Ions?
When writing them as either cation or anion we ...
... put parenthesis around the ion.
Example: ammonium becomes (NH4)+
So ammonium chloride would become (NH4)Cl
Calcium and nitrate CationAnionCa+2NO3-1
Ca(NO3)2Remember: Polyatomic ion goes in parentheses.Example
with Polyatomic Ions
Writing Names
Step 1 Separate cation and anion from formula
CuBr2
Cu2+ Br -
Step 2 Name
Check for the need for a roman numeral in the name.
Transition element? Yes
Special Case on stair-step? Yes
Step 2 Name
Ex: Cu2+ Br-
Copper (II) Bromide
Yourhomeworktests on theseconcepts.
Things to look for
If cations have (), the number is their charge.
If anions end in -ide they are probably off the periodic
table
If anion ends in -ate or -ite it is polyatomic
Properties of Ionic Solids
High lattice energy high melting T3D ionic lattice
brittlenessIons electrical conductivity (whenmolten)solubility in
polar solvents (eg H2O)
Properties of Ionic Compounds
Crystalline structure.
A regular repeating arrangement of ions in the solid.
Ions are strongly bonded.
Structure is rigid.
Crystalline structure
Do they Conduct?
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.
Dissolved in water they conduct.
Ionic solids are brittle
+
-
+
-
+
-
+
-
+
-
+
-
+
-
+
-
Ionic solids are brittle
+
-
+
-
+
-
+
-
+
-
+
-
+
-
+
-
Strong Repulsion breaks crystal apart.
Click to edit the title text format
