Which of the following is a polyatomic ion: CH3COOH, CR2O7^2-, Na^+, or H2?

1 Answer
Dec 13, 2015

Answer:

#[Cr_2O_7]^(2-)# is a polyatomic ion.

Explanation:

Polyatomic ions are ions with charge that are made up of two or more atoms.

For example:

  • #[H_3O]^+#
  • #[SO_4]^(2-)#
  • #[CO_3]^(2-)#

Notice that all of these examples have a charge attached to them. This is what makes them ionic.

Also, all of these ions are made up of more than 2 ions.

Looking through the problem that was given, we have 4 different choices.

First, discard the ones that do not have a charge attached to them. #H^2 and CH_3COOH# do not have charges associated with them, so discard that.

Second, discard the ones that do not have two or more ions in them. #Na^+# is a single sodium ion, so this can be discarded.

Finally, you are left with the last choice: #[Cr_2O_7]^(2-)#. This is your answer.