Oxidation States and
Redox: Oxidation and
Reduction
CT04D01
Science 10
Chemistry
Halogens
Non-metals
Alkali Metals
H
Metaloids
He
Alkaline Earths
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
Fr
Ra
Ac
Rf
Db
Sg
Bh
Hs
Mt
Ds
Weak/Poor Metals
Transition Metals
Lanthanides
Noble Gases
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy Ho
Er
Tm
Yb
Lu
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Fm
Md
No
Lr
Actinides
Es
All elements want to
become like the
noble gases!
H
Li
Ionic
Charges
Alkali Metals – lose 1 e
Alkaline Earths – Lose 2 e
IIIA – Lose 3 e
IVA (carbon) – Lose 4 e / Gain 4 e
He
VA (Nitrogen) – Gain 3 e
VIA (oxygen) – Gain 2 e
Be
B
C
N
O
F
Ne
Al
Si
P
S
Cl
Ar
Halogen – Gain 1 e
Na
Mg
K
Ca
Se
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
Fr
Ra
Ac
Rf
Db
Sg
Bh
Hs
Mt
Ds
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
Noble Gases - neutral
Oxidation Numbers
Oxidation numbers always refer to single atoms
The oxidation number of an uncombined
element is always 0 (this includes diatomics)
(BrINClHOF) Br2, O2, H2,
Ne, Zn, Mg, Ca, etc
The oxidation number of Hydrogen is usually +1
HCl, H2SO4
The oxidation number of Oxygen is usually -2
H2O, NO2, et
Oxidation numbers of monatomic ions follow
the charge of the ion
O2-, Zn2+
The sum of oxidation numbers is zero for a
neutral compound
LiMnO4
The sum of the oxdiation numbers is the
charge of the polyatomic ion
Only when in completely ionic binary compounds
will Alkali Metals (+1), Alkaline Earths (+2),
Halogens (-1)
SO42-, NO3-, PO33NaCl, MgBr2, KF, etc
Polyatomic Ions
The polyatomic ions will be given to you but you should be very
familiar with them by now!! Let’s determine oxidation numbers
for each….
+1
-1
-2
-3
Ammonium
NH4+
Chlorate
ClO3-
Sulfate
SO42-
Phosphate
PO43-
Chlorite
ClO2-
Sulfite
SO32-
Phosphite
PO43-
Nitrate
NO3-
Carbonate
CO32-
Nitrite
NO2Hydroxide
OH-
Practice Assigning Oxidation
Numbers
NO2
N2O5
HClO3
HNO3
Ca(NO3)2
K2CO3
Practice Assigning Oxidation
Numbers
NO2
N= +4, O = -2
N2O5
N = +5, O = -2
HClO3
H=+1, Cl=+5, O = -2
HNO3
H=+1, N = +5, O = -2
Ca(NO3)2
Ca=+2, N =+5, O= -2
K2CO3
K=+1, C=+4, O= -2
Hint: If it includes a polyatomic ion, you know the overall charge,
and oxygen will always be -2, find the other oxidation states next
Practice Assigning Oxidation
Numbers
Fe(OH)3
K3PO3
CO32(NH4)Cl
Fe(ClO2)2
Practice Assigning Oxidation
Numbers
Fe(OH)3
Fe =+3, O=-2, H=+1
K3PO3
K=+1, P=+3, O=-2
CO32-
C=+4, O =-2
(NH4)Cl
N=3-, H=1+, Cl=-1
Fe(ClO2)2
Fe=+2, Cl=3+, O=-2
Redox Equations
NOTE: If you get there! Brakke
students will need to identify
which element is oxidized and
which is reduced for a 7
Oxidation-Reduction Reactions
All redox reactions have at least one
element oxidized and at least one
element reduced
Occasionally the same element may
undergo both oxidation and reduction.


This is known as an auto-oxidation
reduction
We will NOT see this until IB CHEM
Pneumonic Devices….
There are two phrases to help you
remember the general practice of
oxidation and reduction exchanges


LEO says GER
OIL RIG
LEO says…..
GER!
LEO: Loss of Electrons = Oxidation
GER: Gain of Electrons = Reduction
OIL: Oxidation is Loss….
RIG: Reduction is Gain….
….of electrons
Oxidation Numbers
Oxidation is the loss of electrons;
Reduction is the gain of electrons
Oxidation and reduction go together.
Whenever a substance loses electrons
another substance gains electrons
Oxidation Numbers are a system that
we can use to keep track of electron
transfers with a reaction
Using Oxidation Numbers
Careful examination of the oxidation
numbers of atoms in an equation allows us
to determine what is oxidized and what is
reduced in an oxidation-reduction reaction
Using Oxidation Numbers
An increase in the oxidation number indicates
that an atom has lost electrons and therefore
oxidized.
A decrease in the oxidation number indicates
that an atom has gained electrons and
therefore reduced
Example
0
Zn
+
+2 +6 -2
+2 +6 -2
CuSO4 
ZnSO4 +
Zn: 0  + 2  Oxidized
Cu: +2 
0  Reduced
0
Cu
Exercise
For each of the following reactions find
the element oxidized and the element
reduced
Cl2
Cu
+
KBr

KCl +
Br2
+ HNO3  Cu(NO3)2 + NO2 + H2O
HNO3 +
I2
Look
 HIO3
+
on the following slides for answers……
NO2
Exercise 1
For each of the following reactions find the
element oxidized and the element reduced
0
Cl2
+1 -1
+
KBr
+1 -1

KCl +
0
Br2
Br increases from –1 to 0  Oxidized
Cl decreases from 0 to –1  Reduced
K remains unchanged at +1
Exercise 2
For each of the following reactions find the
element oxidized and the element reduced
0
Cu
+1 +5 -2
+2 +5 -2
+4 –2
+1 -2
+ HNO3  Cu(NO3)2 + NO2 + H2O
Cu increases from 0 to +2  Oxidized
Some N in nitric acid from +5 to +4  Reduced
The nitrogen that ends up in copper nitrate remains
unchanged, same for hydrogen and oxygen
Exercise 3
For each of the following reactions find
the element oxidized and the element
reduced
1 +5 -2
0
HNO3 +
I2
+1 +5 -2
 HIO3
+4 -2
+
NO2
N is reduced from +5 to +4  Reduced
I is increased from 0 to +5  Oxidized
The hydrogen and oxygen remain unchanged.