How does radiation speed up a chemical reation?

Answer 1

Radiation can speed up a chemical reaction by promoting electrons to different energy levels, changing the reactivity of the atom/molecule. If radiation was not present, one may have to wait for this promotion to happen spontaneously, which can take far longer. Different electron configurations within an atom can also change the number of bonds that can be readily formed.

For example, the electron configuration in carbon is 1s2 2s2 2p2. There are two unpaired electrons in the p orbital, which could readily make a total two bonds. However, carbon often makes four bonds. This occurs because one of the 2s2 electrons gets promoted to the unoccupied p orbital. The electron configuration changes to 1s2 2s1 2p3, which then has four unpaired electrons which allows it to readily form four bonds. The unpaired electrons are more obvious when the electron configuration is written in this form: 1s2 2s1 2px1 2py1 2pz1. The electrons in each of the p orbitals, as well as the 2s orbital can readily form bonds in this configuration.

Answer 2

Radiation can speed up a chemical reaction by providing energy to break chemical bonds within the reactant molecules. This increases the rate of collisions between molecules and enhances the likelihood of successful reactions occurring. The extra energy supplied by radiation can also facilitate the activation of reaction pathways that may have higher energy barriers to overcome.