Radicals (often referred to as free radicals) are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative or zero charge.Radicals form due to homolytic cleavage of bonds.
Alkyl radicals are radicals formed from alkanes. For example methane CH4 is methane, after a homolytic cleavage of C-H bond, it will form CH3. methyl radical.