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

(a) N$_{2}$H$_{2}$ (b) SO$_{3}$
(a) N$_{2}$H$_{2}$ The name of this compound is dinitrogen dihydride. Hydrogen should be the second element of this molecular compound since it is bonded to nitrogen, which is in Group 5A. When hydrogen is bonded to elements in Groups 6A and 7A, then it is named as the first element. The number of atoms of each element is denoted by a subscript immediately to the right of the element to which it pertains, unless there is only one atom of that element in the compound. (b) SO$_{3}$ The name of this molecular compound is sulfur trioxide. Oxygen is always the last element named in molecular compounds unless it is paired with fluorine. The number of atoms of each element is denoted by a subscript immediately to the right of the element to which it pertains, unless there is only one atom of that element in the compound.