redox

• oxidation

  loss of electrons
• reduction

  gain of electrons
• rules for assigning oxidation states

  1. an uncombined element has an oxidation state of zero
  2. some elements have the same oxidation state in all their compounds
  3. for a compound, the oxidation state of each atom in the compounds formula counts seperately and the numerical sum is zero
  4. for an element existing as an ion the oxidation state is the charge on the ion
  5. for compound ions the sum of the oxidation states of the atoms is the charge on the ion
• oxidation (oxidation state)

  increase in oxidation state
• reduction (oxidation state)

  a decrease in oxidation state
• oxidising agent

  species that accepts electrons
• reducing agent

  a species that donates electrons