Answer
(a) nitrogen trifluoride: NF$_{3}$
(b) phosphorus pentabromide: PBr$_{5}$
(c) sulfur dichloride: SCl$_{2}$
Work Step by Step
To name a molecular compound, we keep the name of the first element as-is, adding a prefix denoting the number of atoms of that element that are present in the compound only if that number is greater than one. For the second element in the compound, we change the ending of the element to $-ide$ and add a prefix reflecting how many atoms of that element are in the compound.
To write molecular formulas given the structural formulas, we follow the following list: C, P, N, H, S, I, Br, Cl, O, F; therefore, the element that appears earlier in the list goes first, and the one that appears later in the list goes second.
(a) nitrogen trifluoride: NF$_{3}$
(b) phosphorus pentabromide: PBr$_{5}$
(c) sulfur dichloride: SCl$_{2}$
