Substances that possess definite volume and shape
are categorized as solids. Solid substances are usually rigid and hard due to
closely packed and well ordered arrangement of atoms, ions or molecules among
each other in a solid material. These entities cannot move randomly without the
aid of energy. On the basis of particular arrangement of atomic, ionic or
molecular species the solids can be divided into two fundamental classes given
as follows
1) Crystalline
solids
2)
Amorphous solids
1. Crystalline solids:
Crystalline solids possess a specific regular
arrangement of atoms, ions or molecules in a three dimensional pattern. Crystalline
solids are further divided into four parts which are given as follows
a) Ionic
solids
b) Molecular
solids
c) Covalent solids
d) Metallic
solids
a) Ionic solids
Building materials of these solids are positive and negative ions which made up an ionic compound. An electrostatic force of attraction binds these oppositely charged ions together in an ionic substance. These solids show high boiling and melting points and brittleness. Ionic solids are not good conductors in solid phase but conduct electricity in molten state. Sodium chloride (NaCl) is an example of ionic compounds.
b) Molecular solids
Constituents of molecular solids are atoms and molecules which bind within a molecular compound through London dispersion forces, dipole-dipole interaction or hydrogen bonding. These substances possess lower melting and boiling points and are somehow flexible as compared to aforementioned ionic solids. Sucrose is an example of molecular substances.
c) Covalent network or atomic solids
These solids are made up of atoms held together via covalent bonds. These solids have high melting and boiling points but on the other hand are bad conductors. Diamond and graphite are common examples of these solids.
d) Metallic solids
The metallic building blocks of this type of solids are bind together through metallic bonds. These solids show good conducting efficiency and high melting points. Metallic solids are categorized into hard, soft as well as malleable solids.
2. Amorphous solids:
These solids do not possess definite arrangement of atoms which do not allow these to contain a definite geometry as well. Molecules mostly arranged randomly, nevertheless there exists some arrangement between a few molecules. These solids possess totally divergent properties as compared to their crystalline counterparts.
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