Oxidation, reduction and redox reactions

• Uncombined elements always have an oxidation state of 0
• Ions always have an oxidation state which is the same as their charge
• Group 1 elements always have an oxidation state of +1
• Group2 elements always have an oxidation state of +2
• Aluminium has an oxidation state of +3
• Hydrogen has an oxidation state of +1 except in hydrides where it is -1 e.g NaH
• Chlorine has an oxidation state of -1 unless in a compound with F and O- it would have a positive value

  e.g. Cl has a value of +3 in ClF3
• Fluorine always has an oxidation state of -1
• Oxygen has an oxidation state of -2 except it is -1 in peroxides and +2 in OF2