Redox Reactions

An element can have several oxidation numbers , based on reactivity , excitation and Group Number .

Highest Oxidation Number :

For s-block : Group Number

For p-block : Group Number - 10

Oxidation ----> Loss of Electron (Remember 'O' of Oxidation stands for "Loss" )

Redox     -----> Gain of Electron

Oxidizing agent increases the other element's oxidation state , while itself undergoing reduction .

The opposite is applicable for Reducing Agent .

**Oxidation States of Elements**

**Note : The positive oxidation states show ionic bonding while negative oxidation state shows covalent bonding in Metals . In Non Metals , the positive oxidation shows covalent bonding while negative shows ionic bonding . Covalent Bond will never proceed oxidation number +4 or -4 .**

Hydrogen (1)         +1 | -1

Lithium     (3)         +1

Berylium   (4)         +2

Boron       (5)         +1 +2 +3

Carbon     (6)        +4 +3 +2 +1  |  -1 -2 -3 -4

Nitrogen    (7)         +1 +2 +3 +4 +5  |   -3 -2 -1     (Nitrogen forms ionic as well as covalent bond ; ionic will result in gain of maximum 3 electrons (Reduction ) covalent will result in loss of maximum 5 electrons (oxidation) )

Oxygen      (8)        +2 +1 | -1 -2

Fluorine     (9)        -1

Sodium      (11)      +1 | -1

Magnesium (12)     +2 +1

Aluminium   (13)     +3 +2 +1 | -1 -2

Phosphorous(14)   +5 +4 +3 +2 +1 | -1 -2 -3

Sulphur         (15)   +6 +5 +4 +3 +2 +1 | -1 -2

Chlorine       (17)    +7 +6 +5 +4 +3 +2 +1 | -1

Potassium     (19)   +1 | -1

Calcium         (20)   +2 +1 | -1

Chromium   (24)    +6 +5 +4 +3 +2 +1 | -1 -2     -4

Manganese (25)   +7 +6 +5 +4 +3 +2 +1 | -1 -2 -3

Iron              (26)  +6 +5 +4 +3 +2 +1 | -1 -2

Copper        (27)  +1 +2 +3 +4

Zinc             (28)  +1 +2

**Important Notes :-**

**1) Noble Gases : Expected Oxidation Number is 0 due to unreactive nature . But ,**

**Krypton(36) shows +2 ; Xenon (54) shows +2 +4 +8 +10 ; Radon(86) shows + 2 +6 .**

**Helium , Neon and Argon show 0 oxidation state .**

**2) All Metalloids show -4 -3 -2 -1 | +1 +2 +3 +4 Oxidation states . Carbon(6) , Silicon(14) , Arsenic(32) , Tin(50) , Lead(82) are metalloids belonging to Group 14 .**

**Oxidation States of some Groups**

CN -1

SO4  -2

OH -1

N3H -----> Hydrozoic Acid

##### H2SO5 -------> Caro's Acid

H2S2O8 ------> Perosulphuric acid or Marshall's Acid

Metal with Carbonyl Group (CO) has 0 oxidation number .

For removal of one mole , 1 Farad current is needed .

1 Farad = 96500 Couloumb

(From Electrochemistry)

**Types of Redox Reaction**

**Combination : X + Y ------> Z**

**Decomposition :  Z -------> X + Y**

**Displacement : XY + Z -------> X + ZY**

**Disproprtionation :** The oxidation State of a single reactant changes into two other oxidation states in the products .

**e.g.  Cl2 + H2O -------> HCl + HOCl**

**0    +1 -2            +1 -1  +1 -2 +1**

Here , Chlorine has two oxidation states in the products section ---> -1 and +1 .

K2Cr2O7 and KMnO4 are the most important oxidizing agents .

K2CrO7 in acidic medium -----> Oxidition State of Chromium =+ 3 ... For Cr2 =+ 6 (Exchange of 6 electrons)

KMnO4 in acidic medium ------> Oxidation State of Manganese =+ 2 (Exchange of 5 electrons )

KMnO4 in basic medium --------> Oxidation State of Manganese =+ 4 (Exchange of 3 electrons )

Equivalent Weight

**Molecular Weight
 Equivalent Weight = ----------------------------------------------------No. of electrons gained or lost**