The names of the compounds FeS, NaCl, NaOH, and Pb₃N₂ all end in the suffix "-ide".

Here's why:

* FeS: Iron sulfide

* NaCl: Sodium chloride

* NaOH: Sodium hydroxide

* Pb₃N₂: Lead nitride

These compounds are all binary ionic compounds, meaning they are composed of two elements, a metal and a nonmetal. In naming these compounds, we use the "-ide" suffix for the nonmetal anion.