Overall Reaction photon ( :C+C1: First propagation step H H H- H H一C H一CI H H methane chlorine atom methyl radical hydrogen chloride Second propagation step H H H-C. H一C-C CI methyl radical chlorine molecule chloromethane chlorine atom H H HCH+C一CI heat or light H-H-CI+H一C H H methane chlorine chloromethane hydrogen (methyl chloride) chloride Chapter 4 8 Chapter 4 8 Overall Reaction