2b. Predicting Formulas of Compounds

Hector claims that a single sodium ion and a single oxygen ion do not bond together to form a stable binary ionic compound. Is he correct? Why or why not?

• Hector is incorrect. The two ions have opposite charges, so they will bond together in a binary ionic compound.

• Hector is incorrect. The two ions have more than eighteen protons, so they will bond together in a binary ionic compound.

• Hector is correct. The sum of the charges of the two ions must be zero in order for them to form a stable ionic compound.

• Hector is correct. The sum of the protons of the two ions must be divisible by eight in order for them to form a stable ionic compound.

Calcium (Ca) is in the second column of the periodic table and is classified as an alkaline earth metal. Which of the following formulas shows the ratio of a compound formed from calcium and iodine (I)?

• CaI

• Ca₂I

• CaI₂

• CaI₂

Potassium (K), an alkali metal, and magnesium (Mg), an alkaline earth metal, both combine readily with bromine (Br), a halogen. What compound will each element (K and Mg) most likely form with bromine?

• KBr and Mg₂Br

• KBr and MgBr

• K₂Br and Mg₂Br

• KBr and MgBr₂

What is the formula for the compound formed when aluminum ions (Al³⁺) and chloride ions (Cl^-) unite?

• AlCl

• Al₂Cl

• AlCl₂

• AlCl₃

Which of the following correctly represents an ion pair and the ionic compound that the two ions form?

• Pb⁴⁺, O^2-, Pb₂O₄

• Sc³⁺, S^2-, Sc₂S₃

• Ba²⁺, O^2-, BaO₂

• Ca^2-, F^-, Ca₂F

Unknown element W has 2 valence electrons. Unknown element X has 7 valence electrons. Which formula shows the most likely outcome when elements W and X react?

• WX

• WX₂

• W_2X

• W₂X₂