Syllabus Edition

First teaching 2014

Last exams 2024

|

Deducing Oxidation Numbers (DP IB Chemistry: SL)

Revision Note

Test yourself
Stewart

Author

Stewart

Last updated

Deducing Oxidation Numbers

  • The oxidation numbers of all other atoms in their compounds can vary
  • By following the oxidation number rules, the oxidation number of any atom in a compound or ion can be deduced
  • The position of an element in the periodic table can act as a guide to the oxidation state

Oxidation Numbers & The Periodic Table

  • Test your understanding on the following examples:

Worked example

State the oxidation number of the atoms in blue in these compounds or ions

a) P2O5

b) SO42-

c) H2S

d) Al2Cl6

e) NH3

f) ClO2-

Answers:

Electrochemistry Table 2_Oxidation Numbers, downloadable AS & A Level Chemistry revision notes

Are oxidation numbers always whole numbers?

  • The answer is yes and no
  • When you try and work out the oxidation of sulfur in the tetrathionate ion S4O62- you get an interesting result!

 

The oxidation number of sulfur in S4O62- is a fraction

  • The fact that the oxidation number comes out to +2.5 does not mean it is possible to get half an oxidation number
  • This is only a mathematical consequence of four sulfur atoms sharing +10 oxidation number
  • Single atoms can only have an integer oxidation number, because you cannot have half an electron!

You've read 0 of your 10 free revision notes

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Stewart

Author: Stewart

Expertise: Chemistry Lead

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Exam Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.