| A | B | 
| oxidation number of an element is | zero | 
| Oxidation number of sodium in sodium compounds is always | +1 | 
| Oxidation number of potasium  in ptassium compounds is always | +1 | 
| chlorine in Cl2 - oxidation number is | 0 | 
| Cl in NaCl oxidation number is | -1 | 
| oxidation number of O in its compounds (not with F)is always | -2 | 
| oxidation numbe rof F in its compounds is always | -1 | 
| sum of oxidation numbers of elements ina compounds | 0 | 
| oxidation number of Al in its compounds is always | +3 | 
| oxidation number of H in its compounds (apart from with metals)is always | +1 | 
| oxidation number of Mg in its compounds is always | +2 | 
| oxidation number of Ca in its compounds is always | +2 | 
| the oxidation number of an element in a simple ion is | the charge on the ion | 
| the sum of the oxidation numbers in a oxoanion is | the sum of the oxidation numbers | 
| in ClO(-) if O = -2 Cl is | +1 | 
| in ClO3(-) if O = -2 Cl is | +5 | 
| in ClO4(-) if O = -2 Cl is | +7 | 
| oxidation is loss (of e) reduction is | gain in e | 
| OIL... | RIG | 
| Na --> Na(+) is | oxidation | 
| Cl2 --->  Cl(-) | reduction | 
| This is oxidation | Fe(2+) ---> Fe(3+) | 
| This is reduction | Fe(3+)  --->  Fe(2+) | 
| If Cl2 -->  ClO(-)  +  Cl(-) | it's disproportionation | 
| Disproprtionation is when the same reactant.. | is oxidised and reduced in the same reaction | 
| In SO4(2-) the oxidation number of S | is ....... in SO4(2-) | 
| The oxidation number of S is +4 ... | in SO2 | 
| the oxidation number of S is -2 ... | in Na2S | 
| If SO4(2-) changes to S(2-) | the S has gained 6e | 
| If SO4(2-) changes to S(2-) S has been ... | reduced |