Talk:Dissociation (chemistry)

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Dissociation / Ionization

"The process is frequently confused with ionization." Okay, but what is the difference? Eleland 02:36, 7 August 2007 (UTC)[reply]

Isn't the introductory paragraph contradictory? Dissociation in chemistry and biochemistry is a general process in which ionic compounds (complexes, or salts) separate or split into smaller particles, ions, or radicals, usually in a reversible manner. For instance, when a Brønsted-Lowry acid is put in water, a covalent bond between an electronegative atom and a hydrogen atom is broken by heterolytic fission, which gives a proton and a negative ion. '

It defines dissociation as a phenomenon of ionic compounds and then cites molecular acids as examples, even citing their covalent nature. Is it that dissociation is the separation of ions in an already ionic compound of the formation of those by heterolytic fission, or both? It should be clearer.

wbrigg 11:12, 16 January 2015 (GMT)

Dissociation is when a molecule falls apart, ionisation is just losing electrons. There are several processes that can give a molecule energy, things like electron impact, (multi) photon impact, third body impact, etc., with each having the posibilty of leaving the molecule in some other state;

Considering just electron impact, sorted in rough energy order;

Elastic Scattering	AB + e^- → AB + e^-
Dissociative Attatchment	AB + e^- → A + B^-
Electronic Excitation	AB + e^- → AB* + e^-
Ionisation	AB + e^- → AB⁺ + 2e^-
Impact Dissociation	AB + e^- → A + B + e^-

All of these processes go via an intermediary, AB⁺ (which may or may not be in some excited state), and then depending on how much energy the AB⁺ has, it then results in one of the steps above. Generally speaking, the more energy it has, the more bits and pieces the molecule falls apart into - you can think of that pretty simply just as the number of bonds you have to break.

There are essentially three things you can do to a molecule, excite it, break it up, or add to it. Where "break it up" here covers both pulling out electrons (ionisation), and pulling off atoms (dissociation). You can combine all of them though, and it just results in combining the words together really, so there is also a thing called dissociative ionisation, which does exactly what you'd guess.

tldr: dissociation is breaking the molecule apart, ionisation is knocking, specifically, electrons out.

Ionization means formation of ions by any means. Yes, removal of electrons from a neutral molecule is ionization, but dissociation of an uncharged aqueous acid can also be described as ionization. For example, CH₃COOH → H⁺ + CH₃COO^-, or more accurately CH₃COOH + H₂O → H₃O⁺ + CH₃COO^-. See the article on Acid dissociation constant, which for neutral molecules is also known as Acid ionization constant. Dirac66 (talk) 02:50, 17 January 2015 (UTC)[reply]

Need a Simple English Wikipedia

I think this article needs a Simple English Wikipedia version of the article Dissociation. Qwertyxp2000 (talk | contribs) 08:39, 8 July 2015 (UTC)[reply]