The collision theory states that chemical reactions can occur when atoms,ions,and molecules collide. Activation energy is needed to disrupt electronic configurations. Reaction rate is the frequency of collisions with enough energy to bring about a reaction. Reaction rate can be increased by enzymes or by increasing temperature or pressure. • The collision theory states that chemical reactions can occur when atoms, ions, and molecules collide. • Activation energy is needed to disrupt electronic configurations. • Reaction rate is the frequency of collisions with enough energy to bring about a reaction. • Reaction rate can be increased by enzymes or by increasing temperature or pressure