Types of Solids
Solids can be crystalline or amorphous. A crystalline solid is one in which the atoms, ions, or molecules lie in an orderly array. An amorphous solid is one in which the atoms, ions, or molecules lie in a random arrangement, as in glass or rubber. Crystalline or true solids can be classified as follows.
Molecular Solids
A molecular solid is one that consists of atoms or molecules held together by intermolecular forces. The physical properties of molecular solids varies greatly. For example, ice melts at 0 oC while sucrose melts with decomposition at 184 oC.
Metallic Solids
A metallic solid is one that consists of positive cores of atoms held together by a surrounding sea of electrons. The delocalized electrons are from the outer shells of the metallic atoms. This type of solid also has physical properties that vary over a wide range.
Ionic Solids
An ionic solid is one that consists of ions, cations and anions held together by the electrostatic attraction of opposite chaeges.
Covalent Network Solids (Macromolecular Solids)
A covalent network is one that consists of atoms held together in large networks by covalent bonds. One can think of a covalent network solid as a giant molecule. In this type of solid inter- and intra-molecular forces are indistinguishable.
A Summary of Properties of Types of Solids
Type of Solid | Melting Point | Hardness | Conductivity |
Molecular | Low | Soft to Brittle | Nonconducting |
Metallic | Varies | Variable Hardness Malleable | Conducting |
Ionic | High to Very High | Hard and Brittle | Nonconducting Solid Conducting Liquid |
Covalent Network | Very High | Very Hard | Usually Nonconducting |