Homolytic cleavage, also known as homolysis, is a type of bond breaking process in which each part of the σ bond takes one electron away, resulting in each product containing a single electron/09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage). This process is also called radical fission, and it often produces free radicals. Homolytic cleavage is represented by an arrow with a single barb, which is used to show single electron transfer specifically/09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage). Homolysis occurs mainly for non-polar bonds, and heat or light is needed to provide enough energy for initiating the process/09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage). For example, the photolytic bromination of methane involves homolytic bond cleavage in the chain initiation mechanism step/09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage). In contrast, heterolytic cleavage is another type of bond-breaking process, in which one part of the bond takes both electrons of the bond away/09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage). Heterolysis is represented by an arrow with double-barbs, which is used to show the transfer of the electron pair specifically/09%3A_Free_Radical_Substitution_Reaction_of_Alkanes/9.01%3A_Homolytic_and_Heterolytic_Cleavage).