What is the chemistry behind amalgamation?

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An amalgam is simply an alloy of some metal with mercury.

Alloys are simply solid solutions with metals. Since the mixture of multiple elements disrupts the metal bonding, the properties are often quite different than the components. (In some cases, alloys form so-called intermetallic compounds with defined stoichiometry, but more often, the ratios are very flexible.)

I wouldn't describe the mixture as a reaction, in much the same way that I wouldn't really call dissolving sodium chloride in water as a reaction. You're forming a mixture. Water disrupts the ionic bonding in NaCl, and mercury and other metals can also accept other components or impurities.

Gallium does alloy with a lot of metals, and indium-gallium eutectic alloy is a liquid at room temperature, as is "galinstan".

As to your question about mercury dissolving the metal atoms, consider that mercury is also a metal, so it also participates in similar metal bonding.

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baharini
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Updated on August 01, 2022

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  • baharini
    baharini over 1 year

    Mercury can form amalgams with metals, such as gold, however how exactly does the "reaction" if you can call it that take place?

    My understanding of metal bonds is that the atoms of a metal are surrounded by a "sea" of electrons, however I don't understand how mercury can "penetrate" metals and weaken their structure or "dissolve" them.

    How does it do this? Also does this apply to Gallium?

    • Brinn Belyea
      Brinn Belyea about 9 years
      The liquid mercury atoms collide with solid metal atoms and bonds form. The atoms in metals move when they are above 0K.
    • Mörre
      Mörre about 9 years
      To expand on Geoff's answer below, if you are interested in knowing more I recommend MIT course 3.091 Solid State Chemistry which is about such things exactly. It is available for free on edX: edx.org/course/mitx/mitx-3-091x-introduction-solid-state-269‌​1