Two crystalline materials, X and Y, were examined in the laboratory. Selected observations are listed below.
• X has a melting point of approximately 1500∘C, is brittle, does not conduct electricity in the solid state, but the melt conducts an electric current.
• Y has a melting point of approximately 900∘C, is malleable when struck with a hammer, and conducts electricity in both the solid and liquid states.
Answer the following questions about the identity of the two materials.
(a) Identify the general type of solid (metallic, ionic, molecular, covalent network, or alloy) represented by X and by Y.
(b) For each material, cite TWO specific observations from the list above and explain how each observation is consistent with the structure and bonding characteristic of the solid you identified in part (a).