The core idea of the collision theory is manifested in the notion that reactions only occur when particles collide with each other. In addition, the colliding particles must carry enough energy for the reaction to occur. The overall orientation of the particles is also critical for the reaction since they need to be oriented accordingly. In short, according to the collision theory, the factors affecting reaction rates include collisions, orientation, and activation energy levels. When applying the framework, the key elements are a steric factor, collision frequency, and activation energy per unit, as well as other important chemical variables, such as temperature, concentration, and constants (Gottfried 418). Therefore, the collision theory is comprised of three core factors as well as additional variables.
It is important to note the fact that activation sources can be different. Reactions between ions in solution occur with small activation energy, which is required to dehydrate the ions. Reactions between free atoms and radicals do not require activation energy since atoms and radicals are active species (Timberlake 107). In homogeneous gas reactions, the main source of activation is collisions, the proportion of which is determined by the Boltzmann distribution law and increases with temperature. Activation can also be caused by external causes, such as the absorption of light quanta during photochemical reactions, the action of electrical discharges, the impact of electrons, a-particles, neutrons, and other radiations (Gottfried 423). In heterogeneous catalytic reactions, the sources of activation can be the changes that occur in the reacting molecules when they are adsorbed by the catalyst surface.
In the event of a collision of active molecules, there must be a well-defined arrangement in the space of the active groups that make up the molecule, which would ensure the formation of final products. The steric factor, in most cases, characterizes the probability of a certain geometric configuration of particles in a collision. The collision theory, with its comparatively simple treatment of the problems of chemical kinetics, has explained many different factors. However, at the same time, because of its schematic nature, it led to contradictions with observations. The method of active collisions does not explain the influence of the solvent, pressure, additions of inert gases, and other factors on the reaction rate (Gottfried 460). It does not allow a theoretical assessment of the steric factor, and to a certain extent, the theory of absolute reaction rates is deprived of these shortcomings.
It should be noted that when utilizing the collision theory in practice, the predictions can be made with differential perspectives or measures. In some cases, the movement and interaction of molecules can be described with the help of the hard sphere model. In other variations, the interaction of molecules with each other takes place, taking into account the forces of intermolecular interaction based on the potential (Gottfried 378). In both cases, the collision check can be performed only for those particles that are closest to each other, that is, those for which the greatest probability of collision occurs. It is important to state that taking into account the forces of intermolecular interaction might not have a significant effect on the simulation result under the physical conditions considered. However, the prime factors still remain relevant and critical for the predictive potential of the theory, which are collisions, orientation, and activation energy levels.