ALEKS Placement Chemistry Practice Exam

The formula for the perchlorate ion is ClO4(-). This ion consists of one chlorine atom (Cl) surrounded by four oxygen atoms (O). The negative charge indicates that the ion has one more electron than protons, giving it an overall negative charge of one. Understanding the naming and structure of polyatomic ions can help clarify this: "per" in perchlorate indicates that it has the maximum number of oxygen atoms typically associated with chlorine in its highest oxidation state, which, in this case, is +7. The chlorate ion (ClO3(-)) has one less oxygen than perchlorate, indicating it holds a lower oxidation state for chlorine. Similarly, the chlorite (ClO2(-)) and chloride (Cl(-)) ions have even fewer oxygen atoms and represent lower states or simpler forms of chlorine oxidation, making them distinctly different from perchlorate. Recognizing the systematic naming conventions based on oxygen content allows one to confidently identify the formula for the perchlorate ion as ClO4(-).