Final answer:
Option a, that ionic compounds have a tendency to melt easily, does not describe ionic compounds accurately because they have high melting points.
Step-by-step explanation:
The property of ionic compounds that does not describe them is that they have a tendency to melt easily. Ionic compounds are characterized by having high melting points due to the strong electrostatic attractions between their cations and anions. These attractions form a crystalline lattice that is hard and brittle. In their solid state, ionic compounds do not conduct electricity; however, when dissolved in water or melted, they become excellent conductors due to the mobility of the ions.
Thus, option a, stating that ionic compounds tend to melt easily, does not accurately describe them, as high melting points are a hallmark feature of ionic solids. Options b, c, and d accurately describe ionic compounds: b) they consist of positive and negative ions, c) they are held together by electrostatic attraction, and d) they have a very ordered structure. The ionic bond's strength contributes to these properties, which are significant in both understanding ionic compounds and predicting their behavior in various conditions.