One of the most important questions to ask of a material is whether it is molecular or non-molecular. Molecular materials include all gases, water, sugars, most organic species etc. We can thus speak of the molecularity of a substance, and molecular substances tend to have intrinsically LOWER melting points, and boiling points than non-molecular substances.
Non-molecular materials include network solids, metals, polymers..........and of course the smallest part of a such a material is a formula unit. So let us take a simple example, NaCl, or CaCO3, which materials are of course non-molecular, and consist of an infinite array of sodium ions, and chloride ions, or calcium ions, and carbonate ions........And the smallest part of this material is of course the NEUTRAL species, the formula unit, NaCl or CaCO3.
Claro....?
