Oxidation and Reduction

• Disproportionation

  When one species is both oxidised and reduced simultaneously
• Oxidation

  The loss of electrons, gain of oxygen, increase in oxidation number
• Reduction

  The gain of electrons, loss of oxygen, decrease in oxidation number
• Oxidising agent

  a substance which oxidises another substance and in doing so becomes reduced (electron acceptor)
• Reducing agent

  a substance which reduces another substance and in doing so becomes oxidised (electron donors)
• Oxidation number (oxidation state)

  Refers to the distribution of electrons
• What are oxidation states based on

  Electronegativity
• Rules for oxidation states

  1. On simple ions, oxidation state is the charge on the ion (e.g Cu2+ Cu +2)

  2.in uncombined elements, the oxidation state is always 0 (e.g Cl2 Cl 0)

  3.the total of all oxidation states must always equal the overall charge on the species

  4.In molecules and more complex ions, the more electronegative element is assumed to be the negative ion
• Peroxide

  X2O2
• Hydrogen-oxidation state in a compound and example

  oxidation state in a compound- +1

  Example- H in H2O
• Hydrogen exception and example

  -1 with metals (hydride)

  Example- NaH
• Group 1-oxidation state in a compound and example

  oxidation state in a compound- +1

  Example- Na in NaCl
• Group 2-oxidation state in a compound and example

  oxidation state in a compound- +2

  Example- Mg in MgCl2
• Aluminium-oxidation state in a compound and example

  oxidation state in a compound- +3

  Example- Al in AlCl3
• Oxygen-oxidation state in a compound and example

  oxidation state in a compound- -2

  Example- O in MgO
• Oxygen exceptions and example

  1) in peroxides, oxygen is -1

  E.g H2O2

  2) +2 with fluorine (because fluorine is more electronegative)

  E.g F2O
• Fluorine-oxidation state in a compound and example

  oxidation state in a compound- -1

  Example- F in NaF
• Why is there no exception for fluorine

  Because it is the most electronegative element
• Chlorine-oxidation state in a compound and example

  oxidation state in a compound- -1

  Example- Cl in NaCl
• Chlorine exception and example

  With Fluorine or oxygen

  E.g HClO, ClF3, HClO3
• Oxidation state group 4

  +4 to -4
• Oxidation state group 5

  +5 to -3
• Oxidation state group 6 (sulfur and below)

  +6 to -2
• Oxidation state group 7 (Bromine and below)

  +7 to -1
• d2 transition metals oxidation states

  Max +4
• d3 transition metals oxidation states

  Max +5
• d4 transition metals oxidation states

  Max +6
• d5 transition metals oxidation states

  Max +7
• d6 transition metals oxidation states

  Highest seen is +6
• Transition metals usually have

  Positive oxidation states
• Oxidation state features

  Always a positive and negative number between -8 and +8 (or 0)
• Highest oxidation state

  +8
• Lowest oxidation state

  -8
• OIL RIG

  oxidation is loss, reduction is gain
• Reduction will only occur with

  Oxidation