According to collision theory, which conditions must be met for a reaction to occur?

The correct understanding of the conditions necessary for a reaction to occur, according to collision theory, emphasizes the importance of both collision and proper orientation of the reacting particles. Collision theory states that for a chemical reaction to take place, reactant particles must collide with sufficient energy and in the correct orientation to break existing bonds and form new ones.

First, consider that a mere collision between particles does not guarantee a reaction; they must also be oriented in such a way that allows the reactive parts of the molecules to interact effectively. This means that when particles collide, they should be aligned properly to enable the necessary interactions at the molecular level.

Additionally, while having enough energy is important for breaking bonds, simply having high-energy collisions without considering orientation may not lead to successful reactions. Therefore, the essential criteria combining both the collision of particles and their proper orientation highlight the complete picture of what is necessary for a reaction to occur.

Thus, combining these two aspects from collision theory makes the correct answer clear: both collision and proper orientation are required for a successful chemical reaction.