 Oxidation Reduction Reaction (Redox): A reaction in which electrons are transferred from one substance to another.

 Oxidation cannot occur without reduction  Definition of Oxidized: 1. Losing of electrons (LEO) 2. Increasing the ox. number, ie: 0 to to Gaining oxygen  Definition of Reduced: 1. Gaining of electrons (GER) 2. Reducing the ox. number, ie: -1 to -2 1 to 0 3. Losing oxygen 

 2Mg + O 2  2MgO  Mg atom transfers two electrons to each oxygen atom.  As a result 2 Mg atoms become Mg 2+ and two oxygen atoms become O 2-  Mg loses two electrons  O gains two electrons

 2Mg + O 2  2MgO  Mg atom transfers two electrons to each oxygen atom.  As a result 2 Mg atoms become Mg 2+ and two oxygen atoms become O 2-  Mg loses two electrons  O gains two electrons

 Can oxidation occur without reduction?  What are the three definitions of oxidation?  What are the three definitions of reduction?  What is a way to remember oxidation/reduction in terms of transfer of electrons?  Does the oxidation number increase or decrease when there is oxidation?  Does the oxidation number increase or decrease when there is reduction?

 When an electron is lost (An electron is found on the product side) there is oxidation ◦ X 0  X +1 + e -  When an electron is gained (An electron is found on the reactant side) there is reduction ◦ e - +Y +1  Y 0

startfinish  Ex5 Na 0  Na +1  Ex6 Fe +3  Fe +2  Ex7 N +1  N +2  Ex8 Mg +2  Mg 0 +1e - 1e e - 2e - + (LEO)oxidized (GER)reduced (LEO)oxidized (GER)reduced

 Whatever is oxidized is called the reducing agent  Whatever is reduced is called the oxidizing agent

startfinish  Ex5 Na 0  Na +1  Ex6 Fe +3  Fe +2  Ex7 N +1  N +2  Ex8 Mg +2  Mg 0 +1e - 1e e - 2e - + oxidized reduced oxidized reduced reducing agent oxidizing agent reducing agent oxidizing agent

 What is a reducing agent?  What is a oxidizing agent?  Are metals generally oxidized or reduced?  Are nonmetals generally oxidized or reduced?

Redox Rules to Learn For Ionic and Covalent bonds

 Definition: Electonegativity is the atom’s ability to attract electrons.  Fluorine is the most electronegative element

Increase EN More protons to attract electrons Decrease EN electrons get further away from protons

Oxidation number of an uncombined atom = zero (no compounds or ions) i.e.Mg, H 2, Na ie. All H 2 O 2 N 2 Cl 2 Br 2 I 2 F 2 ’s ox. # are zero

Oxidation number of a monatomic ion = charge of the ion i.e.Mg 2+, O 2-, Al 3+, Br

The sum of the oxidation numbers of a neutral compound = 0 i.e.H 2 OCO 2 CO NaCl +1 2(+1) = (-2) = =0 +1 =0

The oxidation number for H is +1 Exception: when bonded to a less electronegative element (metal), then it is -1. i.e.LiH, NaH, MgH 2 Exception i.e.HF, HCl

Oxygen’s oxidation number is -2, in a compound Two exceptions: peroxides and fluorine in H 2 O 2 with OF (+1)+ 2( ?) = 0 ? = -1 where O is -1 2(-1) ? + = 0 +2 where O is +2 fluorine (more electronegative)

Oxidation number of polyatomic compound = zero polyatomic ion = the charge of the ion i.e. compounds: NH 3 SiCl 4 K 3 PO 4 i.e. ions: NH 4 + CO 3 2- SO 4 2- NO (+1) = (1) = +1

Oxidation numbers for metals in: Group 1A metal compound +1 2A metal compound +2 3A Aluminum compound +3 i.e. NaClMgSO 4 AlPO 4 +1 = = ? + 4(-2) +6 = 0

 The most electronegative element fluorine ALWAYS has an oxidation number of -1 when it is bonded to another element.  i.e.HF

 Assign oxidation numbers to each element 1. Cl 2 2. Cl- 3. MgCl 2 4. NaH 5. HCl 6. K 3 PO 4 7. CaSO 4 8. KF

 If oxidation number goes up it is oxidized.  If oxidation number goes down it is reduced.

Balance the reactions, write the oxidation numbers for each atom and write the oxidizing and reducing agents. Ex1HCl + Zn  ZnCl 2 + H (-1) =0 Loss of electron oxidation (LEO) Gain of electron reduction (GER) Oxidizing agent Reducing agent

Ex2 Mg + N 2  Mg 3 N 2 Ex3H 2 S + Cl 2  HCl + S Ex4Fe+ O 2  Fe 2 O 3

 There are three definitions of oxidation and reduction:  OxidationReduction Losing of electrons (LEO) Gaining oxygen Increasing oxidation # Losing oxygen Decreasing oxidation # Gaining of electrons (GER)

L E O goes G E RO I L R I G OSEOSE LECTRONSLECTRONS XIDATIONXIDATION AINAIN LECTRONSLECTRONS EDUCTIONEDUCTION XIDATIONXIDATION S OSINGOSING EDUCTIONEDUCTION S AININGAINING