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Metals (Structure of materials (Macrostructure, Microstructure,…
Metals
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Atomic Bonding
Metallic bond
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free electron can move rapidly to electric fields, hence metals are good conductor of electricity
free electrons can transmit kinetic energy rapidly, hence metal are good conductors of heat
the layers of atoms in metal are hard to pull apart because of the electrons holding them together, hence metal are tough
individual atoms are not held to any other specific atoms, hence atoms slip easily past one another, thus metals are ductile
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because their valence electron are not fixed in any one direction, most pure metals are good electrical conductor of electricity
Covalent bond
covalent bonding are characterized by bonds that are formed by sharing of valence electron among two or more atoms
for example, silicon atom, has valence of four, obtains eight electrons in outer shell by sharing its electron with four surrounding silicon atom
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as result diamond C, silicon carbide SIC, Silicon nitride all exhibit covalency
these materials also exhibit very high melting points which could be useful for high temperature applications
Ionic bond
when more than one type of atom is present in a material, one atom may donate its valence electrons to a different atom, filling the outer energy shell of the second atom
both atoms have filled outer energy level, but both have acquired an electrical charge & behave as ions
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Van de Waals bond
sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral molecules -(1)
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