Redox Reaction

REDOX Reaction: A chemical reaction where one substance loses electrons (oxidation) and another gains electrons (reduction).

Oxidation:
- Definition: Losing electrons.
- Mnemonic: OIL (Oxidation Is Losing).
Reduction:
- Definition: Gaining electrons.
- Mnemonic: RIG (Reduction Is Gaining).
Electron Transfer:
- Involves the transfer of electrons between atoms, ions, or molecules.
- Examples: Burning of fuels, corrosion of metals, photosynthesis, and cellular respiration.

Definition: The oxidation number changes when an atom, molecule, or ion gains or loses an electron in redox reactions.

Element Alone:
- An element alone has an oxidation number of 0.
- Example: O₂ has an oxidation number of 0 since it is not involved in any electron exchange.
Simple Ions:
- The charge of a simple ion is its oxidation number.
- Example: Na⁺ = +1, Cl⁻ = -1.
Oxygen:
- Mostly has an oxidation number of -2 (takes electrons).
- Example: In H₂O, oxygen is -2 and hydrogen is +1.
Hydrogen:
- Generally +1 (shares electrons), except in metal hydrides (e.g., NaH where it is -1).
Sum in Neutral Compounds:
- The sum of oxidation numbers in a neutral compound equals 0.
- Example: In CO₂, since O is -2, C must be +4 to balance.
Sum in Ions:
- The sum of oxidation numbers in an ion equals the ion's charge.
- Example: In SO₄²⁻: O is -2 (4 O's = -8), so S must be +6.

Reducing Agent (RA):
- The substance that donates electrons and is oxidized.
Oxidizing Agent (OA):
- The substance that accepts electrons and is reduced.