Writing Formulas

Ion X has a charge of 2+, and ion Y has a charge of 1−. What is the formula unit of the compound formed from the ions?

• XY₂

• X₂Y

• XY

• X₂Y₃

What is the ionic ratio of aluminum to oxygen in the ionic compound aluminum oxide (Al₂O₃)?

• one to three

• three to one

• two to three

• one to two

The anion that has the formula ClO⁻ is called the

• chlorate ion

• hypochlorite ion

• chloride ion

• chlorite ion

What is the formula of calcium phosphate, which is made up of the ions Ca²⁺ and PO₄³⁻?

• Ca₆PO₄

• Ca₃PO₄

• Ca₃(PO₄)₂

• Ca₂(PO₄)₃

Which of the following statements is true about the ammonium ion (NH₄⁺) and the phosphate ion (PO₄³⁻)?

• ammonium: monatomic anion; phosphate: monatomic cation

• ammonium: polyatomic cation; phosphate: polyatomic anion

• ammonium: monatomic cation; phosphate: monatomic anion

• ammonium: polyatomic anion; phosphate: polyatomic cation

Which of the following gives an incorrect formula? (BONUS QUESTION)

• iron(II) sulfite; FeSO₃

• aluminum phosphate; AlPO₄

• magnesium hydroxide; Mg(OH)₂

• silver carbonate; AgCO₃