Diamond is an example of which solid type?

• A. Covalent-network Solids
• B. Ionic Solids
• C. Molecular Solids
• D. Metallic Solids

Answer: (A)

The solid type is defined by how atoms are bonded throughout the material. Diamond forms a continuous three-dimensional network of very strong covalent bonds between carbon atoms. Each carbon is sp3-hybridized and bonded to four neighbors in a tetrahedral arrangement, creating an infinite framework with no discrete molecules. This covalent-network structure is why diamond is incredibly hard, has a very high melting point, and conducts electricity poorly in its pure form—there are no delocalized electrons or mobile ions to carry charge.

Other solid types differ in bonding and structure. Ionic solids are built from alternating positive and negative ions in a lattice and tend to be hard and brittle, often conducting electricity only in molten state or when dissolved. Molecular solids consist of discrete molecules held together by weaker van der Waals or hydrogen bonds, usually with much lower melting points. Metallic solids feature a lattice of positive cores with a sea of delocalized electrons, which makes them good conductors and often malleable.

Diamond, as a covalent-network solid, exemplifies how a rigid, extended covalent network determines its standout properties.