What are free radicals?

Free radicals are molecules or atoms that possess one or more unpaired electrons. This unpaired state makes them highly reactive, as they tend to seek out other electrons to pair with in order to achieve a more stable electronic configuration. The presence of unpaired electrons is the key characteristic of free radicals, leading to their involvement in various chemical reactions, often resulting in the formation of new compounds.

In contrast, stable and non-reactive entities do not have unpaired electrons, which is why the first option does not describe free radicals accurately. The third option mentions bonding participation, which does not specifically address the unique behavior of free radicals in which their reactivity is tied to the unpaired electrons rather than bond formation. Lastly, describing free radicals as non-charged molecules overlooks their inherent instability and reactivity due to the presence of unpaired electrons, further distinguishing them from stable molecules.