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 KMnO4are 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 = undefinedNo. of electrons gained or lostundefined'''undefined