Question

what is the ion $\ce{clo4-}$ named?
\chloride ion
\chlorite ion
\hypochlorite ion
\perchlorite ion
\perchlorate ion

Explanation:

To name the polyatomic ion $\ce{ClO4^-}$, we use the rules for oxyanions. Oxyanions with chlorine (Cl) and oxygen (O) follow a naming pattern based on the number of O atoms. The ion $\ce{ClO4^-}$ has 4 oxygen atoms. The prefix "per-" is used for the maximum number of oxygen atoms in a chlorine oxyanion, and the suffix "-ate" is used for the more common (higher oxygen) oxyanions. So $\ce{ClO4^-}$ is named perchlorate ion.

• Chloride ion is $\ce{Cl^-}$, so that's incorrect.
• Chlorite ion is $\ce{ClO2^-}$, so that's incorrect.
• Hypochlorite ion is $\ce{ClO^-}$, so that's incorrect.
• Perchlorite ion would be an incorrect form (the correct with 4 O is perchlorate, and the -ite suffix is for fewer O; the correct -ite for chlorine with 3 O is chlorite, but with 4 O, we use -ate with per- prefix).
• Perchlorate ion matches the formula $\ce{ClO4^-}$.

Answer:

E. perchlorate ion