Chapter 2 - Questions and Problems - Page 78: 2.83

a) nitrogen trichloride b) iodine heptafluoride c) tetraphosphorus hexaoxide d) disulfur dichloride

For each of the molecular compounds, the naming strategy is to name the first element of the compound first, and then name the second element. In the case of the first element, we add a prefix corresponding to the number of atoms of that element that is present in the compound, but we keep the name of the element exactly the same as in the elemental form. The exception is if there is only one atom of that element in the compound; then, we do not add a prefix to the name of the element. For the second element of the compound, we add a prefix to the name of the element and change the ending to "-ide." a) We have a single nitrogen atom as the first element, so we keep the name "nitrogen" without adding a prefix or changing the ending. For the second element, chlorine, because we have three of them, we add the prefix "tri-" to chlorine and change the ending "-ine" to "-ide." Thus, we come up with the name "nitrogen trichloride." b) We have a single iodine atom as the first element, so we keep the name iodine without adding a prefix or changing the ending. For the second element, fluorine, because we have seven of them, we add the prefix "hepta-" to fluorine and change the ending "-ine" to "-ide." Thus, we come up with the name "iodine heptafluoride." c) We have phosphorus as the first element, so we keep the name nitrogen and add the prefix "tetra-" to reflect that there are four phosphorus atoms. For the second element, oxygen, because we have six of them, we add the prefix "hexa-" to oxygen and keep the "ox-" in oxygen and add the ending "-ide." Thus, we come up with the name "tetraphosphorus hexaoxide." d) We have sulfur as the first element, so we keep the name sulfur and add the prefix "di-" to reflect that there are two sulfur atoms. For the second element, chlorine, because we have two of them, we add the prefix "di-" to chlorine and change the ending from "-ine" to "-ide." Thus, we come up with the name "disulfur dichloride."