3 Forms of Chemical
Equations
1) Molecular
 Form you are most familiar with
 Reactants and products written as neutral compounds
 Ex. KCl + NaF  NaCl + KF

Chemical Equations (cont. )
2) Full Ionic
 All chemical compounds are written as ions if they can be (ex. Strong electrolytes, strong acids, strong bases, etc.)
 Ex. Ba +2 + 2Cl + 2Na + + SO
4
BaSO
4 (s)
+ 2Na + + 2Cl -
-2 

How do we write a FULL
IONIC equation?
 Insoluble compounds are written as SOLIDS
 Pure liquids and gases are written as is, not broken up into ions, electrically neutral.
 Which compounds are broken up into ions????
 Soluble ionic compounds
 Strong acids (HCl, HBr, HI, HNO
3
, HClO
4
 Strong Bases ( Group IA bases and Ca(OH)
2
, H
2
SO
4
)
, Sr(OH)
2
, Ba(OH)
2

Forms of Chemical Equations
(cont.)
3) Net Ionic Equations
 Next step after full ionic equation.
 Elimination of Spectator Ions (ions found on both sides of the equation, not changed with reaction)
 Includes chemical compounds and ions
DIRECTLY involved in chemical reaction.

Example 1:
Na
2
CO
3
+ Ca(NO
3
)
2
 2NaNO
3
+ CaCO
3
(s)
Write net ionic equation

Example 2:
 Magnesium metal reacts with HCL to produce a solution of magnesium chloride and hydrogen gas.
 Write the molecular equation and net ionic equation.

Oxidation-Reaction???? It’s more common than you think……..

Oxidation Numbers/State
 Allows us to identify redox reactions
 A change in these numbers------ REDOX
REACTION ! ! !
 Acts like all chemical compounds are ionic----gives atom a charge it would have
IF it was ionic

Oxidation Numbers
 No physical meaning
 Assigned to atoms to aid in redox reactions
 Treats all atoms as if they were ions
 ACTUAL charge of monoatomic ions, ASSIGNED charge to molecular atoms/atoms with a polyatomic ion

Oxidation Number Rules
 Priority 1 st , if there is ANY conflict—go with highest priority
1) Sum of oxidation numbers = 0 for ALL neutral compounds (atoms, molecules)
 Any single atoms are also assigned oxidation # = 0

Rule # 1 Examples
 Br
2
 MgCl
2
 C
6
H
12
O
6
 Cu
 Ag
 Fe

Oxidation Number Rules
2) Sum of oxidation numbers for an ion = ion’s charge
Examples:
 SO
4
-2
 NH
4
+
 Al ion
 Cl ion

Oxidation Number Rules
3) Group 1A metals = +1
Group 2A metals = +2
Examples: MgSO
4
K
3
PO
4

Oxidation Number Rules
4) For the majority of chemical compounds—
 F = -1
 H = +1 (sometimes will have -1)
 O = -2
Examples: NH
3
H
2
O
CO
HF
KF

Oxidation Number Rules
5) Group 7A Elements = -1
Group 6A Elements = -2
Group 5A Elements = -3
**When combined with a metal in a binary compound !

 CaF
2
 Li
2
S
 Mg
3
N
 K
3
P
Rule #5 Examples

Ex 1. Al
2
O
3
 Assign Oxidation Numbers

Ex. 2 K
2
Cr
2
O
7
 Assign Oxidation Numbers

1) S
8
Calculate the oxidation number of Sulfur in the following:
6) SO
2
2) H
2
S
3) ZnS
4) SF
4
5) SF
6
7) SO
3
8) SO
3
-2
9) SO
4
-2
10) H
2
SO
4

Let’s Practice !
 Strategy: assign oxidation numbers you know 1 st
1) Cr
2
O
7
-2
2) CaH
2
3) KClO
4
4) Fe
3
O
4
5) Al
2
O
3
6) K
2
Cr
2
O
7