1. Oxidation state OR Oxidation Number in Compounds, Ions, and elements.
Priority
1. All group 1 is +1
2. All group 2 is +2
3. Hydrogen is +1
4. Oxygen is -2
*F is more electronegative than O, so we prioritize F than O
All elements is 0
All compounds are neutral
COMPOUNDS
a. SO2
S=+4 O=-2
+4 -4
ClF3
-3
ICl3 I=+3
-3
N2H4
-4 +4
b. IONS
SO4 2+6 -8
Cl=+3
N=-2
S=+6
Sn2+
Sn=+2
NO3+5 -6
N = +5
O=-2
PO43+5-8
(NH4)2 SO4 S=+6
SO42+6 -8
NH4+
-3+4
-6 +8 +6 -8 = 0
WHY PRIORITY?
H2O2 H=+2 O=-2
+4 -4
H2 O 2
+2-2
H=+1 O=-1
NaH
+1-1
CORRECT
WRONG
CORRECT
NaH WRONG
-1 +1
2. -Redox based on electrons OIL-RIG
Mg
282
à Mg2+ + 2e- (Oxidation)
28 2
Cl2 + 2e- à 2Cl-
(Reduction)
-Redox based on Oxidation number/state
*NOT ALL REACTIONS ARE REDOX
NaBr + Cl2 à NaCl + Br2
+1-1. 0.
+1-1. 0
Reduction (Oxidation number decreases)
Cl2 + 2e- à 2ClOxidation
2Br- à Br2 +- 2e
a. Cl2 à 2Cl- (ignore the coefficient)
0
-1
2I- à I2 Oxidation
-1
0
b. 4Fe + 3O2 à 2Fe2O3 +6 -6
0
0
+3 -2
NaOH + HCl à NaCl + H2O
REDUCTION