Materials classification — malleability and ductility in solids Which class of solids is characteristically both malleable (can be hammered into thin sheets) and ductile (can be drawn into wires), as typically observed in engineering metals?

Introduction / Context:
Malleability and ductility are hallmark mechanical properties used to distinguish classes of solids in materials science. Understanding which bonding type permits layers of atoms to slip without catastrophic fracture is essential for selecting materials for forming processes such as rolling, drawing, and stamping.

Given Data / Assumptions:

• Malleability: ability to deform in compression into thin sheets without cracking.
• Ductility: ability to deform in tension into wires without breaking.
• Classes considered: metallic, ionic, covalent (network), and molecular solids.

Concept / Approach:
Metallic solids are held together by a non-directional metallic bond where valence electrons are delocalized, producing a 'sea of electrons'. This bonding allows atomic planes to slide under stress while maintaining cohesion, enabling extensive plastic deformation. In contrast, ionic solids have strong directional electrostatic attractions; shifting planes brings like charges adjacent, causing brittle failure. Covalent network solids (e.g., diamond, silica) have rigid, highly directional bonds that resist plastic flow, leading to brittleness. Molecular solids are bound by weak van der Waals forces; they are soft and often low-melting, not typically malleable or ductile in the engineering sense.

Step-by-Step Solution:
Identify the property pair (malleability + ductility) required for metalworking operations.Relate to bonding: non-directional metallic bonding accommodates slip systems.Evaluate alternatives: ionic and covalent networks fracture rather than plastically flow; molecular solids deform poorly and lack structural integrity.Therefore, the correct selection is metallic solids.

Verification / Alternative check:
Common metals (gold, silver, copper, aluminum, low-carbon steel) are routinely rolled into sheets and drawn into wires in industrial practice—direct empirical confirmation of malleability and ductility inherent to metallic bonding and crystal slip systems.

Why Other Options Are Wrong:
Ionic solids are brittle due to repulsive like-charge alignment upon slip; covalent network solids resist plasticity because bonds are highly directional; molecular solids lack strong bonding needed for structural ductility.

Common Pitfalls:
Confusing 'softness' with ductility—molecular solids may be soft but not ductile; also assuming all metals are equally ductile (some, like cast irons, are not metallic solids in the pure sense and are brittle due to graphite/carbide morphology).

Final Answer:
Metallic solids