Final answer:
The response with an error is A. hydroxide / OH- / monatomic / anion; hydroxide is not monatomic, but a polyatomic ion because it consists of oxygen and hydrogen atoms.
Step-by-step explanation:
The response that contains an error is A. hydroxide / OH- / monatomic / anion. Hydroxide (OH-) is not a monatomic ion; rather, it is a polyatomic ion because it consists of more than one atom (oxygen and hydrogen). The rest of the responses correctly classify the ions:
- Carbonate / CO32- / polyatomic / anion
- Ammonium / NH4+ / polyatomic / cation
- Magnesium / Mg2+ / monatomic / cation
- Sulfite / SO32- / polyatomic / anion
The error occurred because hydroxide was incorrectly classified as monatomic, whereas it is actually polyatomic, containing one oxygen and one hydrogen atom.