Activation energy and the activated complex

1. Activation Energy $(Ea)$

• Definition: The minimum kinetic energy needed for a chemical reaction to occur.
• Required to break bonds in the reactant molecules.
• Can be supplied in the form of heat, light, or mechanical energy.

2. Activated Complex

• A temporary, unstable, high-energy intermediate between reactants and products.
• Exists for a very short time before forming products or reverting to reactants.

3. Types of Reactions Based on Activation Energy

Reaction Type	Description
Spontaneous Reaction	Reactants already have enough energy to start the reaction without additional energy.
Non-Spontaneous Reaction	Reactants lack sufficient energy and need an external energy source to start.

🔹 Hint: "Spontaneous" means the reaction occurs on its own, without external interference.

4. Key Takeaways

✅ Activation energy is required to initiate a reaction.

✅ The activated complex is a high-energy transitional state.

✅ Lower activation energy → Faster reaction.

✅ Spontaneous reactions occur without extra energy, while non-spontaneous reactions need additional energy.