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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






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