Redox

• Oxidation is the loss of electrons
• Reduction is the gain of electrons
• Oxidation and reduction always occur together in a redox reaction.
• The separate equations showing the oxidation and reduction processes are called half-equations
• The oxidation state of an uncombined element is always zero.
• Match the element group with its oxidation state:

  Group I ↔️ +1

  Group II ↔️ +2

  Group III ↔️ +3
• Oxygen has an oxidation state of -2 in most compounds, except in peroxides where it is -1
• For compound ions, the sum of the oxidation states of the atoms equals the charge on the ion.
• Order the common oxo-anions by their charges:

  1️⃣ -1

  2️⃣ -2

  3️⃣ -3
• Oxidation is an increase in oxidation state
• Reduction is a decrease in oxidation state
• A reducing agent is a species that donates electrons and causes reduction.
• An oxidising agent is a species that accepts electrons.
• Order the steps for balancing complex half-equations:

  1️⃣ Write down the formulae for reactants and products and balance the atoms undergoing redox

  2️⃣ Balance any oxygen atoms by adding water

  3️⃣ Balance hydrogen atoms by adding H+ ions

  4️⃣ Balance the charges by adding electrons
• When combining half-equations, the number of electrons lost must equal the number of electrons gained.