Redox
Oxidation Reduction
Loss of electrons Gain of electrons
Gain of oxygen Loss of oxygen
Increase in oxidation Decrease in oxidation state
Oxidation State: The charge on a simple ion or the difference in the number of electrons associated
with an element in a compound compared with the atoms of the element
Oxidation state of an atom is 0, even diatomic
Always written as +2 not 2+
Fractional oxidation states are possible e.g. Fe304
Oxygen is nearly always -2 except in peroxides e.g. H202 = -1, and in F20, = +2 as fluorine is
more electronegative than oxygen
Group 1 always have an oxidation state of +1
Group 2 always have an oxidation state of +2 in compounds
Oxidation state of simple ions in a compounds= charge on ion e.g. Iron(II) Chloride, Iron= +2
Total of oxidation states in a compound must equal 0
Total of oxidation stats in a molecular ion must equal charge of ion
Oxidation states of P and D block elements vary, with the highest being ‘+group number’
Oxidising Agent: Is an electron acceptor
Reducing Agent: Is an electron donor
An oxidising agent is a chemical that causes oxidation in another species, the reducing agent
causes reduction in another species by being oxidised.
Half Equations
Mg → Mg2+ + 2e-
Cl2 + 2e- → 2Cl-
Balance Oxygen atoms with water.
Balance H atoms with H+
Balance charge with e-
Then, to add together, ensure that each equation has the same no. of e-
One species is reduced and one oxidised
Disproportionation: Reaction in which the same element is oxidised and reduced
Oxidation Reduction
Loss of electrons Gain of electrons
Gain of oxygen Loss of oxygen
Increase in oxidation Decrease in oxidation state
Oxidation State: The charge on a simple ion or the difference in the number of electrons associated
with an element in a compound compared with the atoms of the element
Oxidation state of an atom is 0, even diatomic
Always written as +2 not 2+
Fractional oxidation states are possible e.g. Fe304
Oxygen is nearly always -2 except in peroxides e.g. H202 = -1, and in F20, = +2 as fluorine is
more electronegative than oxygen
Group 1 always have an oxidation state of +1
Group 2 always have an oxidation state of +2 in compounds
Oxidation state of simple ions in a compounds= charge on ion e.g. Iron(II) Chloride, Iron= +2
Total of oxidation states in a compound must equal 0
Total of oxidation stats in a molecular ion must equal charge of ion
Oxidation states of P and D block elements vary, with the highest being ‘+group number’
Oxidising Agent: Is an electron acceptor
Reducing Agent: Is an electron donor
An oxidising agent is a chemical that causes oxidation in another species, the reducing agent
causes reduction in another species by being oxidised.
Half Equations
Mg → Mg2+ + 2e-
Cl2 + 2e- → 2Cl-
Balance Oxygen atoms with water.
Balance H atoms with H+
Balance charge with e-
Then, to add together, ensure that each equation has the same no. of e-
One species is reduced and one oxidised
Disproportionation: Reaction in which the same element is oxidised and reduced
