## Chemistry: Principles and Practice (3rd Edition)

(a) CaCl$_2$; calcium chloride (b) CO$_2$; carbon dioxide (c) Fe$_2$O$_3$; iron (III) oxide
(a) CaCl$_2$; calcium chloride Calcium (Ca) is an alkaline earth metal belonging to group 2 of the periodic table and has a valence of 2+. Chlorine is a halogen belonging to group 17 of the periodic table and has a valence of 1-. Calcium and chlorine combine in a 1:2 ratio in this compound. To name this ionic compound, we keep the name of the cation, calcium, as-is. We then add the name of the anion, chlorine, changing its ending to $-ide$. (b) CO$_2$; carbon dioxide Carbon (C) is a nonmetal belonging to group 14 on the periodic table. Oxygen (O) is in group 16 (or 6A) and has a valence of 2-. In this compound, carbon and oxygen are combine in a 1:2 ratio. To name this molecular compound, we keep the name of the cation, carbon, as-is because there is only one atom of carbon in the compound. For the anion, we add the prefix $di-$ to oxygen to specify that there are two oxygen atoms in the compound. We then change the ending of the anion to $-ide$. (c) Fe$_2$O$_3$; iron (III) oxide Iron is a transition metal that has more than one valence. According to the specifications we are given, we want to use the iron atom with a valence of 3+ such that the ratio of iron to oxygen is 2:3. Oxygen (O) is in group 16 and has a valence of 2-. To name this ionic compound, we keep the name of the cation, iron, as-is and add the Roman numeral III to the right of the elemental symbol. We then add the name of the anion, oxygen, changing its ending to $-ide$.