Chapter 2 - Atoms, Molecules, and Ions: Matter Starts Here - Problems - Page 71: 77

(b)

Option (a) is incorrect. Calcium oxide's formula is written correctly. Calcium has an oxidation number of +2 whereas oxygen has an oxidation number of -2. Therefore, for a neutral compound to exist, the positive and negative charges must equal one another. In this compound, there should be one calcium atom for every oxygen atom. Option (c) is incorrect. Barium sulfide's formula is written correctly. Barium has an oxidation number of +2 whereas sulfur has an oxidation number of -2. Therefore, for a neutral compound to exist, the positive and negative charges must equal one another. In this compound, there should be one barium atom for every sulfur atom. Option (d) is incorrect. Potassium oxide's formula is written correctly. Potassium has an oxidation number of +1 whereas oxygen has an oxidation number of -2. Therefore, for a neutral compound to exist, the positive and negative charges must equal one another. In this compound, there should be two potassium atoms for every oxygen atom. Option (b) is correct. Lithium sulfate's formula is written incorrectly. Lithium has an oxidation number of +1 whereas the sulfate ion has an oxidation number of -2. Therefore, for a neutral compound to exist, the positive and negative charges must equal one another. In this compound, there should be two lithium atoms for every sulfate ion.