Changing the way you learn

4.3 Redox

Oxidation Number
1. Can be thought of as the number of electrons involved in bonding to a different element
  1. Helps when writing formulae and balancing equations as a check that all electrons are counted for
Oxidation Number RULES
1. Always zero for elements
2. Each atom in a compound has an oxidation number
3. An oxidation number has a sign which is placed before the number
Oxidation Numbers
1. Element
2. Oxidation Number
  1. -2
    1. O
    2. CaO
    3. +1
      1. H2S
      2. H
      3. -1
        HF
        F
        +2
        MgCl2, CaO
        Mg 2+, Ca2+
        -1
        HCl, KBr, CaI2
        Cl- , Br- , I-
3. Example
4. Special Cases
  1. Oxidation Numebr
    1. -1
      1. NaH, CaH2
      2. H in metal hydrides
      3. -1
        H2O2
        O in peroxides
        +2
        F2O
        O bonded to F
  2. Element
  3. Example
Using Roman numerals in naming
1. The roman numeral shows the oxidation state (number) of the element, without a sign
  1. E.g/ Iron(II) represents Fe2+ with oxidation number +2
    1. E.g/ Iron (III) represents Fe3+ with oxidation number +3
Redox Reactions
1. Reduction and Oxidation
  1. O.I.L R.I.G
    1. Oxidation Is Loss (of electrons) Reduction Is Gain (of electrons)
  2. Redox reactions involve reduction AND oxidation
    1. If something is reduced, something else must be oxidised
2. Reduction is a decrease in oxidation number
3. Oxidation is an increase in oxidation number

4.3 Redox

	Created by Bee Brittain over 8 years ago