Molecular orbital or band theory

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Alloys

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 When two metals are heatec;l together, or a metal is mixed with a nonmetallic element, then one of the following will occur:  l. An ionic compound may be formed.  2. An interstitial alloy may be formed.  3. A substitutional alloy may be formed.  4. A simple mixture may result.  Which of these occurs depends on the hemical nature of the two elements concerned, and on the relative sizes of the metal atoms and added atoms.
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Super Conductivity

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                                  Super Conductivity   https://en.m.wikipedia.org/wiki/File:Periodic_table_with_superconducting_temperatures.jpg                                Metals are good conductors of electricity, and their conductivity increases as the temperature is lowered. In 1911 the Dutch scientist Heike Kamerlingh Oimes discovered that metals such as Hg and Pb became superconductors at temperatures near absoiute zero.  A superconductor has zero or almost zero electrical resistance: It can therefore carry an electric current without losing energy, and in principle the current can flow for ever. There is a critical temperature.  That which the resistance drops sharply and superconduction occurs. Later, Meissner and Ochsen feld found that some superconducting materials will not permit a magnetic ...
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Theories of bonding in metals

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  The honding and structures adopted hy metals and alloys arc less fully understood than those with ionic and covalent compounds. Any successful theory of metallic bonding must explain both the bonding between a large number of identical atoriJs· in a pure, metal, and the bonding between widely different metal atoms in alloys. The the.ory cahnot involve directional bonds, since most metallic properties remain even when the metal is in the liquid state (for example mercury), or when dissolved in a suitable solvent (for example solutions of sodium in liquid ammonia). Further, the theory should explain the great mobility of electrons.
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