Oxidation and Oxidation and ReductionReduction

OxidationOxidationThe chemical process by which an The chemical process by which an

element or compound gains element or compound gains oxygenoxygen. .

Example: 2Mg(s) + OExample: 2Mg(s) + O22 2MgO 2MgO Oxidation naturally happens to every Oxidation naturally happens to every

metal except platinum and gold.metal except platinum and gold. Oxidation can also be applied to any Oxidation can also be applied to any

element or compound which element or compound which gives upgives up electrons in order to form a covalent electrons in order to form a covalent or ionic compounds. or ionic compounds.

Example: Cu(s) Example: Cu(s) Cu Cu+2+2 + 2e- + 2e-

Fe + OFe + O22 Fe Fe22OO33

Ag + O2 Ag2O

Oxygen cause food to spoil by Oxygen cause food to spoil by oxidation!oxidation!

ReductionReduction The chemical process by which an element The chemical process by which an element

or compound or compound losesloses oxygen. oxygen. This is how metal is refined. The oxygen is This is how metal is refined. The oxygen is

removed in order to “reduce” metals to removed in order to “reduce” metals to their elemental form.their elemental form.

Example: 2 ZnO Example: 2 ZnO 2 Zn + O 2 Zn + O22

Reduction is also applied to any element or Reduction is also applied to any element or compound which compound which gainsgains electrons in order electrons in order to form a covalent or ionic compounds. to form a covalent or ionic compounds.

Example: FeExample: Fe+3+3 + 3e- + 3e- Fe Fe

RedoxRedox This is the name given to any reaction that This is the name given to any reaction that

involves a gain of electrons by one compound involves a gain of electrons by one compound and loss of electrons by another.and loss of electrons by another.

An easy way to remember which is to think of An easy way to remember which is to think of LEO the Lion:LEO the Lion:

LEOLEO the lion says “ the lion says “GERGER”” LLose ose EElectrons— lectrons— OOxidationxidation GGain ain EElectrons— lectrons— RReductioneduction

You can recognize a redox reaction by assigning You can recognize a redox reaction by assigning oxidation numbers to each element in each oxidation numbers to each element in each compound and look to see if they change from compound and look to see if they change from the reactant side to the product side.the reactant side to the product side.

Example 1Example 1:: Assign oxidation numbers first!Assign oxidation numbers first! +2 -1+2 -1 0 +2 -1 0 0 +2 -1 0 CuClCuCl22 + Zn + Zn ZnCl ZnCl22 + Cu + Cu

Species oxidized? ______Species oxidized? ______– Loses electrons - ZnLoses electrons - Zn00 to Zn to Zn2+2+

Species reduced? ______Species reduced? ______– Gains electrons - CuGains electrons - Cu2+2+ to Cu to Cu00

Zn

Cu2+

Example 2Example 2: :

+2 -2 0 0 +4 -2 +2 -2 0 0 +4 -2 2CuO + C 2CuO + C Cu + CO Cu + CO22

Species oxidized? ______Species oxidized? ______– Loses electrons - CLoses electrons - C00 to C to C+4+4

Species reduced? ______Species reduced? ______– Gains electrons – CuGains electrons – Cu+2+2 to Cu to Cu00

C

Cu2+

Oxidizing AgentOxidizing Agent a substance that can cause another a substance that can cause another

substance to be oxidized (lose electrons)substance to be oxidized (lose electrons) Strong oxidizing agents are those that Strong oxidizing agents are those that

want to gain electrons the most, such as want to gain electrons the most, such as Fluorine, oxygen and Chlorine. (they are Fluorine, oxygen and Chlorine. (they are electron hungry!)electron hungry!)

They are the substance that gets reduced!They are the substance that gets reduced! Reducing AgentReducing Agent a substance that can cause another a substance that can cause another

substance to be reduced (gain electrons)substance to be reduced (gain electrons) Strong reducing agents are those that Strong reducing agents are those that

easily give up electrons, such as Na, Li and easily give up electrons, such as Na, Li and KK

They are the substance that gets oxidized!They are the substance that gets oxidized!

ExampleExample

0 -1 -1 00 -1 -1 0 ClCl22 + 2Br + 2Br1-1-(aq) (aq) 2Cl 2Cl1-1-(aq) + Br(aq) + Br22

Species Oxidized = Species Oxidized =

Species Reduced =Species Reduced =

Oxidizing agent = Oxidizing agent =

Reducing agent = Reducing agent =

Loses electrons = Br1-

Gains electrons = Cl2

Cl2

Br1-