What is the correct name for the molecular compound Si_5F_7?

• A. silicon fluoride
• B. pentasilicon heptafluoride
• C. heptasilicon pentafluoride
• D. silicon pentafluoride

Answer: (B)

Verified step by step guidance

1. Identify that the compound Si_5F_7 is a molecular (covalent) compound composed of nonmetals: silicon (Si) and fluorine (F). Molecular compounds use prefixes to indicate the number of atoms of each element.
2. Recall the prefixes for numbers: 1 = mono-, 2 = di-, 3 = tri-, 4 = tetra-, 5 = penta-, 6 = hexa-, 7 = hepta-, etc. These prefixes are used before the element names to indicate the quantity of atoms.
3. Name the first element (silicon) with the appropriate prefix for the number of atoms. Since there are 5 silicon atoms, use the prefix 'penta-' to get 'pentasilicon'. The prefix 'mono-' is usually omitted for the first element if there is only one atom, but here we have 5, so we keep 'penta-'.
4. Name the second element (fluorine) with the appropriate prefix for the number of atoms and change the element ending to '-ide'. Since there are 7 fluorine atoms, use the prefix 'hepta-' and change fluorine to 'fluoride', resulting in 'heptafluoride'.
5. Combine the two parts to form the full name: 'pentasilicon heptafluoride'. This correctly reflects the number of atoms of each element in the molecular compound Si_5F_7.