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

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Answer 1 · 2015-12-13T23:40:19

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

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

For example:

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.