Oxidation & Reduction
- There are three definitions of oxidation and reduction used in different branches of chemistry
- Oxidation and reduction can be used to describe any of the following processes
Definitions and Examples of Oxidation & Reduction
Use the acronym "Oil Rig" to help you remember the definitions of oxidation and reduction
Oxidation States
- The oxidation state of an atom is the charge that would exist on an individual atom if the bonding were completely ionic
- It is like the electronic ‘status’ of an element
- Oxidation states are used to
- Tell if oxidation or reduction has taken place
- Work out what has been oxidised and/or reduced
- Construct half equations and balance redox equations
Oxidation States of Simple Ions
Worked example
What are the oxidation states of the elements in the following species?
a) C b) Fe3+ c) Fe2+ d) O2- e) He f) Al3+
Answers:
a) 0 b) +3 c) +2 d) -2 e) 0 f) +3
- So, in simple ions, the oxidation stateof the atom is the charge on the ion:
- Na+, K+, H+ all have an oxidation state of +1
- Mg2+, Ca2+, Pb2+ all have an oxidation state of +2
- Cl–, Br–, I– all have an oxidation state of -1
- O2-, S2- all have an oxidation state of -2
Examiner Tip
Oxidation state and oxidation number are often used interchangeably, though IUPAC does not distinguish between the two terms.
Oxidation states are represented by Roman numerals according to IUPAC