When two separate pieces of sodium chloride crystals are physically put together, no wonder that they will not fuse with each other.

But I don’t understand why. Ionic bonds are described to be non-directional and bonds should be formed between the sodium ions and chloride ions in the two pieces of sodium chloride crystals.

Why must I melt the two pieces of crystals to fuse them together/ evaporate a solution in which the two pieces of crystals have dissolved?

  • 1
    $\begingroup$ If the surfaces are scrupulously clean, atomically smooth and placed in a vacuum, then two separate crystals will probably fuse after being contacted. It'd be a form of cold welding. $\endgroup$ Nov 15, 2023 at 12:01
  • $\begingroup$ @ Nicolau Saker Neto Why is the fusion impossible at room temperature and pressure? $\endgroup$ Nov 15, 2023 at 12:04
  • 2
    $\begingroup$ Consider surface adsorption of molecules of gases and bad alignment of surface ions of the touching crystals. $\endgroup$
    – Poutnik
    Nov 15, 2023 at 12:07
  • 1
    $\begingroup$ Because you need to place the ions less than a nanometer apart, and in ordinary conditions there'd be jagged edges, grime and air in the way. $\endgroup$ Nov 15, 2023 at 12:07


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