Saturday, June 18, 2011

Classification of Solids

Solids can be classified in various ways. But classification based on binding force distinguishes four types of solids namely ionic solids, covalent solids, metallic solids and molecular solids. The various characteristics of these solids can be tabulated as follows:-
PROPERTY IONIC CRYSTAL COVALENT CRYSTAL METALLIC CRYSTAL MOLECULAR CRYSTAL
Constituent Particles Cations and Anions are held at lattice points Atoms Positive ions (Kernels) and mobile electrons. Small molecules.
Binding Forces Strong electrostatic forces of attraction. Covalent bond forces. Electrical attraction between positive ions and electrons Weak vanderwall’s forces between molecules.
Physical property Brittle, high M. P. & B. P., good conductor of electricity in molten or aqueous solution high heats of fusions. Generally hard, high M. P. & B. P, poor conductors of electricity. High light of fusion. Hardness and M. P vary, good conductor of heat and electricity. Ductile, malleable luster, moderate heat of fusion. Generally soft, low M. P, volatile very poor conductor of electricity and heat, low heat of fusion.
Examples NaCl, KF, CuSO4,   NaNO, NaNO3, KBr, Na2SO4 etc. Diamond, silicon carbide, quartz etc. Cu, Ag, Al, Fe, Na, Pt etc. Solid CO2, Iodine naphthalena etc.

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