Final answer:
The formula for bismuth(V) fluoride, an ionic compound where bismuth has a 5+ charge and combines with fluoride ions, is BiF5.
Step-by-step explanation:
The student is asking for the formula of bismuth(V) fluoride, which is an ionic compound. When naming ionic compounds, the charge of the metal ion is given using roman numerals in parentheses immediately following the metal ion's name. In this case, "V" indicates that bismuth is carrying a 5+ charge. Fluoride is the name given to the fluorine ion when it has gained one electron to form an anion with a 1- charge.
Bismuth, being in its +5 oxidation state as indicated by the (V), will form ions with a charge of 5+. The fluoride ion has a charge of -1. To create a neutral ionic compound, we must balance the total positive and negative charges. Therefore, we will need five fluoride ions to balance the charge of one bismuth(V) ion. The formula for bismuth(V) fluoride is thus BiF5.