Classification of Crystalline Solids
Table: Some characteristics of different types of crystalline solids
| Types of Solid | Constituents | Bonding | Examples | Physical Nature | M.P. | B.P. | Electrical Conductivity |
| Ionic | Positive and negative ions network systematically arranged |
Coulombic
|
NaCl, KCl, CaO, MgO, LiF, ZnS, BaSO4 and K2SO4 etc. | Hard but brittle | High (≃1000K) | High (≃2000K) |
Conductor (in molten state and in aqueous solution) |
| Covalent | Atoms connected in covalent bonds |
Electron sharing
|
SiO2 (Quartz), SiC, C (diamond), C(graphite) etc. |
Hard Hard Hard |
Very high (≃4000K) |
Very high (≃5000K) |
Insulator except graphite |
| Molecular | Polar or non-polar molecules |
(i) Molecular interactions (intermolecu-lar forces) (ii) Hydrogen bonding
|
I2,S8, P4, CO2, CH4, CCl4 etc.
Starch, sucrose, water, dry ice or drycold (solid CO2) etc. |
Soft
Soft |
Low (≃300K to 600K)
Low (≃400K) |
Low (≃ 450 to 800 K)
Low (≃373K to 500K) |
Insulator
Insulator |
| Metallic |
Cations in a sea of electrons
|
Metallic
|
Sodium , Au, Cu, magnesium, metals and alloys | Ductile malleable |
High (≃800K to 1000 K) |
High (≃1500K to 2000K) |
Conductor |
| Atomic | Atoms | London dispersion force | Noble gases | Soft | Very low | Very low | Poor thermal and electrical conductors |
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