— redox → reduction + oxidation
— when an oxygen is gained → oxidation
— oxidation and reduction always occur together
— if a substance loses electrons during a reaction → oxidation
— if a substance gains electrons during a reaction → reduction
O → oxidation
I → Is
L → Losing
R → Reduction
I → Is
G → Gaining
— 2Mg + O2 → 2MgO
Write each substances that react and show whether they gain or lose electron(s) with charge
— left side of the equation (reactants) → gains electrons (reacts with them)
— right side of the equation (products) → gives our electrons (is a product)
e.g → Mg → (Mg2+) + 2e-
→ O + (2e-) → (O 2-)
Make sure elements are in the reactants and the products side of the reaction
e.g → Mg → (Mg2+) + 2e-
→ O2 + 2(2e-) → 2(O 2-)
e.g → Mg → (Mg2+) + 2e-
→ O2 + (4e-) → (2O 4-)
Make sure both half equations have the same number of electrons
e.g → Mg → (Mg2+) + 2e-
→ O2 + (4e-) → (2O 4-)
e.g → 2(Mg) → 2(Mg2+) + 2(2e-)
→ O2 + (4e-) → (2O 4-)
e.g → 2Mg → 2Mg2+ + (4e-)
→ O2 + (4e-) → 2O 4-
** if the two products have the same coefficient (no. of moles) → 1 compound **
** if different coefficients → becomes the molecular number **
— shows the number of electrons gained, loss or shared during a reaction
— elements in groups usually have the same oxidation number as their charge
— sum of oxidation states in a compound always = 0
— this can be used to find oxidation states of some substances
— oxidation → loss of electrons
— reduction → gain of electrons
— increase in oxidation state → the substance has been oxidised
— decrease in oxidation state → the substance has been reduced
— oxidation state of a substance in elemental form = 0
— redox → reduction & oxidation → always occurs together
— if a substance has been oxidised [increase in oxidation state] → another substance has oxidised it → it is the reducing agent
— if a substance has been reduced [decrease in oxidation state] → another substance has reduced it → it is the oxidising agent