Solid is a rigid and incompressible state of matter . Due to high intermolecular forces and less intermolecular distance ,they are very difficult to compress . They have a definite shape and definite volume .
Solids are broadly classified into two types
1. Crystalline Solids
2. Amorphous Solids
1. Crystalline Solids
●Solids in which the constituent particles are arranged in a definite and regular pattern is called as Crystalline Solids.
●They have long range order. It means that the regularity in the arrangement of particles is up to long ranges
● They have sharp melting point . They do not melt at any temperature . When a particular temperature reached they start melting.
● They are anisotropic in nature. It is a property of crystalline Solids to show different properties in different directions is called as anisotropy .
Crystalline Solids can be isomorphous or polymorphous .
Isomorphous
●Two or more Substances having same Crystalline structures are called as isomorphous .
●Isomorphous Substances have same atomic ratio .
Example : NaCl : MgO = 1:1
Polymorphous
A single Substance that can be form two or more Crystalline structure is called as Polymorphous . Alpha-quartz , beta-quartz and cristobalite are some crystalline structure of Silicon dioxide (SiO2) .
It is also called as "Allotropic form " or "allotropy" . The difference between these two terms is that polymorphous is used for Substances but allotropy is used for an element . Example : Carbon can form different allotropes like Diamond , Graphite and fullerene .
2. Amorphous Solids
●Solids in which the constituent particles are not arranged in definite and regular pattern are called as amorphous Solids .
●They have a short range order
●They do not have a sharp melting point . They melt over a wide range of temperature .
●They are isotropic in nature . Solids having same properties in all direction are called as isotropic in nature .
Crystalline Solids are further classified into four types
1. Ionic Solids
2. Covalent Solids
3. Molecular Solids
4. Metallic Solids
1. Ionic Solids
Constituent particles in Ionic Solids are ions . Ions can be cation or anion . These ions are held together by electrostatic force of attraction between opposite charges . They are hard and brittle in nature . They have high melting point . They are bad Conductor of heat and electricity in solid state but good conductor of electricity when melted or dissolved in water.
Examples : NaCl , CaF2 , MgCl2 ...
2. Covalent Solids
Constituent particles in covalent Solids are Covalently bonded atoms . These atoms are held together by strong covalent bonds . They are very hard in nature . Diamond is the hardest Substances Known is a type of Covalent Solids . They have very high melting point . They are bad Conductor of heat and electricity .
Except : ● Graphite : Good Conductor of electricity .
● Diamond : Good Conductor of heat .
3. Molecular Solids
Constituent particles in molecular Solids are Molecules or monoatomic atoms like Helium , Argon , Hydrogen(H2) . These Molecules or atoms are held together by weak forces ( London force , Dipole - dipole force and hydrogen bonding ) . They are soft and have very low melting point . They are very bad Conductor of heat and electricity .
4. Metallic Solids
Constituent particles in metallic Solids are metals and sea of free electrons . These electrons are free to move within the surface of metal . They is strong metallic bond between metal ions and sea of free electrons . They are soft as well as hard in nature . Their melting point also varies from low to very high . They are a good conductor of heat and electricity . They also show properties like malleability , ductility and lustre .
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