Final answer:
A free radical is a highly unstable atom with an unpaired electron in its outermost shell. They can easily bond to other atoms to become stable and are reactive compounds. Free radicals can cause cellular damage and have been associated with diseases like cancer and coronary artery disease.
Step-by-step explanation:
A free radical is a highly unstable atom with an unpaired electron in its outermost shell. Most odd electron species are highly reactive and can easily bond to other atoms in order to become stable. Free radicals can cause cellular damage and have been implicated in various destructive processes in the body, such as cancer and coronary artery disease.