Which of the following is the correct name for N2S5?
The Correct Answer and Explanation is :
The correct name for ( \text{N}_2\text{S}_5 ) is dinitrogen pentasulfide.
Explanation
Chemical names follow the rules of nomenclature established by the International Union of Pure and Applied Chemistry (IUPAC). For molecular compounds like ( \text{N}_2\text{S}_5 ), which consist of two nonmetals (nitrogen and sulfur), the prefix naming system is used. Here’s how the name is derived:
- Identify the elements:
- The first element is nitrogen (N).
- The second element is sulfur (S).
- Determine the prefixes:
- Prefixes indicate the number of atoms of each element. For ( \text{N}_2\text{S}_5 ), there are 2 nitrogen atoms and 5 sulfur atoms.
- The appropriate prefixes are:
- “Di-” for 2 nitrogen atoms.
- “Penta-” for 5 sulfur atoms.
- Construct the name:
- The first element, nitrogen, retains its name (“nitrogen”).
- The second element, sulfur, is modified to “sulfide” (the suffix “-ide” replaces the element’s ending in binary compounds).
- Combining these, the name is dinitrogen pentasulfide.
- Additional Rules:
- The “mono-” prefix is omitted when it applies to the first element in the compound (e.g., CO is “carbon monoxide,” not “monocarbon monoxide”).
- Prefixes are added for clarity in molecular compounds because nonmetals can form multiple compounds with different ratios (e.g., ( \text{NO}_2 ) is nitrogen dioxide, while ( \text{N}_2\text{O} ) is dinitrogen monoxide).
Why is the Name Important?
The systematic naming of compounds avoids confusion. ( \text{N}_2\text{S}_5 ), for instance, is distinct from other nitrogen-sulfur compounds like ( \text{N}_2\text{S}_3 ) (dinitrogen trisulfide) or ( \text{NS}_2 ) (nitrogen disulfide). Each name corresponds uniquely to its molecular structure.