Final answer:
The perchlorate ion, ClO4-, has 4 more oxygen atoms compared to the chlorate ion, ClO3-. The perchlorate ion has 4 oxygen atoms, while the chlorate ion has only 3 oxygen atoms.
Step-by-step explanation:
The perchlorate ion, ClO4-, has 4 more oxygen atoms compared to the chlorate ion, ClO3-. The perchlorate ion has 4 oxygen atoms, while the chlorate ion has only 3 oxygen atoms. Therefore, the answer is (c) 3.