Question

which of the following is considered an anion?
na+
f-
f
na

Explanation:

An anion is a negatively - charged ion. $Na^{+}$ is a sodium cation (positively - charged). $F$ is a neutral fluorine atom. $Na$ is a neutral sodium atom. $F^{-}$ is a negatively - charged fluoride ion, which is an anion.

Answer:

F⁻