Ionic compounds are named by knowing the names of their parts.
The Positive Component (Cation) of an ionic compound will retain its name completely. The Negative Component (Anion) will have its ending changed to -ide (in most cases).
#NaCl#= Sodium Chloride
(See how Chlorine
#CaF_2#= Calcium Fluoride
(The number of Anions doesn't change the answer)
#Na_2S#= Sodium Sulfide
(The number of Cations doesn't change the answer either)
There is much, much more to naming ionic compounds, however, without more information on the specific question I will not write out an entire unit of high school chemistry.