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What is the fundamental difference between chemical adsorption and physical adsorption.

Why do some compounds chemisorb and others physisorb?

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    $\begingroup$ It's the difference between binding to an adsorbent chemically (undergoing a chemical reaction) vs simply binding through attraction, i.e. electrostatic attraction. $\endgroup$ Commented Apr 20, 2016 at 2:21

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It appears to be one of degrees of bonding, without a clear distinction. As stated in this Wikipedia article:

Physisorption, also called physical adsorption, is a process in which the electronic structure of the atom or molecule is barely perturbed upon adsorption.$\mathrm{^{[1][2][3]}}$

A more thorough description is given later in the article:

"The fundamental interacting force of physisorption is caused by van der Waals force. [...] In comparison with chemisorption, in which the electronic structure of bonding atoms or molecules is changed and covalent or ionic bonds form, physisorption, generally speaking, can only be observed in the environment of low temperature (thermal energy at room temperature ~26 meV) and the absence of the relatively strong chemisorptions. In practice, the categorisation of a particular adsorption as physisorption or chemisorption depends principally on the binding energy of the adsorbate to the substrate."

1) K. Oura; et al. (2003), Surface Science, An Introduction, Berlin: Springer, ISBN 978-3-540-00545-2
2) M. C. Desjonqueres; et al. (1996. Corrected printing 1998), Concepts in surface physics (2nd ed.), New York: Springer-Verlag, ISBN 3-540-58622-9
3) Hans Luth; et al. (1993), Surfaces and interfaces of solids, Springer-Verlag, ISBN 978-3-540-56840-7

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