REDOX
Reactions
Oxidation – Reduction
Oxidation – Reduction Reaction
These reactions involve a transfer of
electrons
Half reactions MUST occur simultaneously
Oxidation – loss of electrons
Oxidizing agent – a substance that has the
potential to cause another substance to be
oxidized
Oxidation – Reduction Reaction
Reduction – involves the gain of electrons
Reducing agent – a substance that has the
potential to cause another substance to be
reduced (gain electrons)
Oxidation States
 The oxidation number of a pure element is 0
 The oxidation number of a monatomic ion
equals the charge on the ion
 The more electronegative element in a binary
compound is assigned the number equal to the
charge it would have it were an ion
 The oxidation number of fluorine in a compound
is always -1
 Oxygen has an oxidation number of -2 unless it
is combined with Fluorine, in which it is +1 or +2,
or it is in a peroxide, in which it is -1
Oxidation States
 Hydrogen’s oxidation state in most of its compound
is +1, unless it is combined with a metal, in which
case it is -1
 In compounds, Group 1 and Group 2 elements and
aluminum have oxidation numbers of +1, +2, and
+3 respectively
 The sum of the oxidation numbers of all atoms in
a neutral compound in 0
 The sum of the oxidation numbers of all atoms in a
polyatomic ion equals the charge of the ion
Oxidation
 Oxidation is the process in which atoms or ions of
an element experience an increase in oxidation
states
2 Na (s) + Cl2 (g) 2 NaCl(s)
 Sodium undergoes an oxidation process because
the sodium atoms loses an electron and become a
sodium ion – sodium is an oxidized to a sodium ions
 Electrons are on the right side of the arrow)
0
+1
Na  Na+ + e A species whose oxidation number increases is
oxidized
Reduction
 Reduction is the process in which the oxidation
state of an element decreases
2 Na (s) + Cl2 (g) 2 NaCl(s)
 Each chlorine atom accepts an electrons and
becomes a chloride ion
 Electrons are on the left side of the arrow
Cl2 + 2e-  2Cl A species that undergoes a decrease in oxidation
state is reduced
Oxidation – Reduction Reaction
Lose
Electrons
Oxidation
“Leo” the lion says “Ger”
Gain
Electrons
Reduction