Which is an example of a polyatomic ion?

Well-known examples of such polyatomic ions are the sulfate ion (SO42–), the hydroxide ion (OH–), the hydronium ion (H3O+), and the ammonium ion (NH4+).

Explanation:

is there more context to go with this question? Like a photo?

I will give it my best shot anyhoo

Explanation:

Polyatomic ions: they are covalently bonded groups of atoms and having a positive or negative charge caused by the formation of an ionic bond with another ion.

And if your question is anything like the one I had a few days ago on a test, your answer would be something like "Both hydroxide cation (OH -) and phostphate cation (PO 4 3 -) are polyatomic ions)

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask