How can we choose prefix for the antonyms . please answer? .

Some prefixes like.. a, anti, counter, dis , IL, I'm, in, or, non, mis, un..give negative meanings when they are added as prefixes. Ex : Moral_ amoral Social_ anti social Act- counteract Loyal_ disloyal Ill-advised (il before_l) Impossible (im before_p) Irrelevant (ir before_r) Understand_ misunderstand Certain_ uncertain