Identify redox reactions as reactions involving gain and loss of electrons

🔬 Redox Reactions – Gain and Loss of Electrons

What is a Redox Reaction?

Redox (short for reduction‑oxidation) is a chemical reaction where electrons are transferred between atoms. Think of it as a game of give‑and‑take – one atom gives electrons (gets oxidised) and another receives them (gets reduced). ⚡️

Key Features to Spot a Redox Reaction

  • Atoms change their oxidation numbers.

  • There is a clear electron transfer.

  • Both an oxidation and a reduction half‑reaction can be written.

How to Identify Oxidation and Reduction

  1. Assign oxidation numbers to every element.

  2. Find which atoms change their numbers.

  3. Mark the electron transfer: loss = oxidation, gain = reduction.

Example 1 – Iron Oxidation

\$\ce{Fe + \frac{1}{2}O2 -> FeO}\$

Oxidation numbers: Fe 0 → +2 (loses 2 e⁻), O 0 → –2 (gains 2 e⁻). 🔋

Example 2 – Zinc and Copper

\$\ce{Zn + Cu^{2+} -> Zn^{2+} + Cu}\$

Oxidation: Zn 0 → +2 (loses 2 e⁻). Reduction: Cu²⁺ → Cu 0 (gains 2 e⁻).

ElementOxidation State (Reactant)Oxidation State (Product)Change
Fe0+2+2 (oxidised)
O0-2-2 (reduced)

Exam Tip: Start by assigning oxidation numbers. If any change occurs, you have a redox reaction. Remember: the element that increases its oxidation number is oxidised; the one that decreases is reduced. ??

Quick Practice

  1. Is the following a redox reaction? \$\ce{2H2 + O2 -> 2H2O}\$

  2. Write the oxidation and reduction half‑reactions for \$\ce{Fe + S -> FeS}\$

Remember: Redox = REDuction + OXidation. Think of it as a game of ⚡⚡ where electrons move from one atom to another. Keep practising and you’ll spot them in no time! 🚀