What are the electrical properties of metals, ceramics and polymers by analyzing their structure?

[Kenshin]

I know the obvious stuff that metals conduct anr ceramics can be semiconductors but i failed to find the explanation from their structure
And i also want to know how to compare the melting points and the hardness of ceramics and polymers analyzing their structure.
Also to finish this annoing subject i need to compare the densities of metals, ceramics and polymers refering to their structure.

[jorganos]

Metals: crystals (or liquids) with unlocated electrons forming a cloud which may move easily in an electrical field.

Ceramics: may allow ion conduction, depending on the properties of the crystal lattice. The mechanism often involves ions moving into adjacent fault positions.

Polymers with a mesomeric conjugation along the entire molecule may conduct electricity. Graphite layers are an extreme example for this.


Melting points and hardness of ceramics and polymers may vary.

Ceramics are basically crystallites bonded across the edges via sintering (heating just below the melting point of the constituiting crystallites). This gives them two different "melting points" - the lower one for the bonds created by the sintering process, and another one for the crystallites.

Polymers rarely melt. Chain or layered polymers can soften when the vibration energy exceeds the van der Waals attractions or dipol attractions between the macromolecules.

Polymer hardness often will be anisotropic - soft along the polymer chains or layers, hard across the macromolecules.

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