Chemistry Regents Practice Test

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Prepare for the Chemistry Regents Exam with interactive quizzes and detailed explanations. Study effectively with flashcards and multiple choice questions. Maximize your exam readiness!

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Which of the following ions would have a -3 charge?

Ammonium ion
Phosphate ion
Nitrate ion
Hydroxide ion

The correct answer is: Phosphate ion

The phosphate ion carries a -3 charge due to its chemical structure and the nature of the atoms involved. Phosphate is comprised of one phosphorus atom covalently bonded to four oxygen atoms (PO4). In this configuration, the phosphorus atom typically has a +5 oxidation state, while each of the four oxygen atoms carries a -2 oxidation state. However, because one of the oxygen atoms is a terminal atom and is typically involved in double bonding, the effective charge after considering the overall molecular structure results in the phosphate ion having a total negative charge of -3. The other ions listed do not exhibit a -3 charge. The ammonium ion has a +1 charge, nitrate carries a -1 charge, and hydroxide has a -1 charge as well. This helps to clarify why the phosphate ion is the only ion among the given choices that has a -3 charge.