# What is the difference between a molecule and a crystal

**URL:** <https://boards.straightdope.com/t/what-is-the-difference-between-a-molecule-and-a-crystal/143425>\
**Category:** Factual Questions\
**Created:** [December 17, 2002, 10:02pm UTC](https://boards.straightdope.com/t/what-is-the-difference-between-a-molecule-and-a-crystal/143425 "2002-12-17T22:02:58Z")\
**Posts on this page:** 1\
**Page:** 2

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**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\
**Post date:** [December 23, 2015, 1:20am UTC](https://boards.straightdope.com/t/what-is-the-difference-between-a-molecule-and-a-crystal/143425/21 "2015-12-23T01:20:44Z")

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> [@robert\_columbia](#):
>
> Nitpick: Isn’t covalent bonding part of the fundamental definition of a molecule?

Molecules of ionic compounds are presumably not often encountered in practice, because ionic compounds generally have high boiling points. But they do exist. Gas phase NaCl is shown here to be a mixture of NaCl monomers and dimers.

> **[Accurate equilibrium structures obtained from gas-phase electron diffraction...](https://pubmed.ncbi.nlm.nih.gov/17579381/)**
>
> A novel method has been developed to allow the accurate determination of equilibrium gas-phase structures from experimental data, thus allowing direct comparison with theory. This new method is illustrated through the example of sodium chloride vapor...

> [@](#):
>
> Accurate equilibrium structures obtained from gas-phase electron diffraction data: sodium chloride.  
> McCaffrey PD1, Mawhorter RJ, Turner AR, Brain PT, Rankin DW.

[https://www.era.lib.ed.ac.uk/bitstream/handle/1842/2601/McCaffrey%20PD%20thesis%2007.pdf;jsessionid=52552542FBA223765122707815CD67F0?sequence=2](https://www.era.lib.ed.ac.uk/bitstream/handle/1842/2601/McCaffrey%20PD%20thesis%2007.pdf;jsessionid=52552542FBA223765122707815CD67F0?sequence=2)

> [@](#):
>
> Equilibrium structures from gas-phase electron-diffraction data  
> Philip D. McCaffrey (PhD thesis)

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