What is the name of the molecular compound SF5?
a. sulfur pentafluoride
b. sulfur fluoride
c. monosulfur pentafluoride
d. sulfur(V) fluoride
The correct answer and explanation is:
Correct Answer: a. sulfur pentafluoride
Explanation:
The compound SF₅ is named sulfur pentafluoride based on the rules of naming binary molecular compounds, which are formed between two nonmetals. In such compounds, prefixes are used to indicate the number of atoms of each element present in the molecule.
In SF₅, the two elements involved are sulfur (S) and fluorine (F). The molecule consists of one sulfur atom and five fluorine atoms. The naming follows these steps:
- The first element, sulfur, keeps its elemental name. Since there is only one sulfur atom, the prefix “mono-“ is generally omitted for the first element.
- The second element, fluorine, is modified to “fluoride” when it appears in a compound. The prefix “penta-“ is used to indicate that there are five fluorine atoms.
So, the correct name is sulfur pentafluoride.
Other answer choices are incorrect for the following reasons:
- b. sulfur fluoride is incomplete because it does not specify how many fluorine atoms are bonded to the sulfur atom.
- c. monosulfur pentafluoride is not standard nomenclature. Although there is one sulfur atom, the prefix “mono-“ is not typically used for the first element if only one atom is present.
- d. sulfur(V) fluoride uses a naming convention typically applied to ionic compounds or compounds involving metals and oxidation states, not binary molecular compounds between two nonmetals like sulfur and fluorine.
Therefore, the IUPAC-compliant name for SF₅, following the correct molecular compound naming rules, is sulfur pentafluoride.