(1) an effective collision between reacting particles
Explanation:
In order for a chemical reaction to occur, an effective collision between reacting particles must always be.
Based on the collision theory, for reactions to occur, there must be collisions between the reacting particles.
It implies that the rate of reaction depends on the number of collision per unit time as well as the fraction of this collision that is successful or effective.
For collisions to be effective, they must have adequate energy.
