Which of the following ions is an oxyanion? 1. F - 2. SO42 - 3. NH4 + 4. SCN-

An anion is a negatively charged ion, meaning that the ion gained one or more electrons, thus became negatively charged.

An oxyanion is an anion that contains at least one oxygen atom bounded to other element (s)

Checking the choices given, we will find that the only oxyanion is:

(SO4) 2-