Talk:Intermolecular force/Comments

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I suggest that this article should follow the (in my view excellent) summary at www.chem.wilkes.edu/~peters/index_files/intrabonds.ppt. Perhaps invite Greg Peters of Wilkes University Chemistry department to participate? (peters@wilkes.edu)

Hmschallenger (talk) 18:43, 4 June 2009 (UTC)


This article is bad from start.

In the first part:

One should start to talk about ideal gases and why the ideal gas model fails to predict intermolecular bonding. This assumption is not present in the text, and is the basis for the entire description of intermolecular forces, either classical, or quantum mechanics.

In physics, chemistry, and biology (Why not just 'In Nature' ?), intermolecular forces are forces that act between stable molecules or between functional groups of macromolecules (It is not specified the kind of 'action', hence, this phrase does not in any away contribute do define anything, and *non-stable* molecules, such as radicals, also show this kind of interactions!). Intermolecular forces (aka van der Waal's forces) include momentary attractions between molecules, diatomic free elements, and individual atoms (There is a need to specify what other kinds of 'interactions' occurs within intermolecular forces, or rewrite the whole phrase). They differ from covalent and ionic bonding in that they are not stable (This phrase must be rewritten. Intermolecular interaction is not so *strong as*, and due to its nature, it's shortlived), but are caused by momentary polarization of particles (Nonsense! Is covalent bond *due to* momentary polarization of particles? Rewrite!). Because electrons have no fixed position in the structure of an atom or molecule, but rather are distributed in a probabilistic fashion based on quantum probability, there is a positive chance that the electrons are not evenly distributed and thus their electrical charges are not evenly distributed. See Schrödinger equation for the theories on wave functions and descriptions of position and velocity of quantum particles.(Rewrite this! This should be shorter and not so extended! If you wish to speak of this, place it in a new subchapter! And by the way, where are the references for van der waals equation? and for the lack of interpretation provided by ideal gas equation? those are a whole lot more important here!)

In general one distinguishes short and long range van der Waal's forces. The former are due to intermolecular exchange and charge penetration (What is intermolecular exchange and charge penetration? One can't just put names! at least put a link to an article that explains it! intermolecular exchange is not so trivial as this part of the text might lead to think!). They fall off exponentially as a function of intermolecular distance R and are repulsive for interacting closed-shell systems (An equation, followed by this explanation would be a nice coming!). In chemistry they are well known(Suggestion: This effects are well-known in physical chemistry, due to the fact that they give rise...), because they give rise to steric hindrance, also known as Born or Pauli repulsion. Long range forces fall off with inverse powers of the distance, R-n, typically 3 ≤ n ≤ 10, and are mostly attractive.(This paragraph needs to be rewritten! It's too confusing!)

The sum of long and short range forces gives rise to a minimum, referred to as Van der Waal minimum (Some equations would be nice! And the references? I haven't seen one single reference YET!). The position and depth of the Van der Waal's minimum depends on distance and mutual orientation of the molecules.(I suggest some figures here, to enhance understanding) "General theory" This is because before the advent of quantum mechanics the origin of intermolecular forces was not well understood. Especially the causes of hard sphere repulsion, postulated by Van der Waals (OH! Only know you speak of the most important part? And what is the hard sphere repulsion? Just a name?), and the possibility of the liquefaction of noble gases were difficult to understand. Soon after the formulation of quantum mechanics, however, all open questions regarding intermolecular forces were answered, first by S.C. Wang and then more completely and thoroughly by Fritz London. (There is no logical historical sequence in this introduction! I strongly recommend a cleanup in this part! Author should mention the ideal gas model as not being able to explain intermolecular forces (such as liquifying gases), van der Waals theory and equation, Keesom work on permanent dipole-permanent-dipole, Debye's work on the permanent-dipole-induced-dipole, and London's QM work on induced dipole, induced dipole. There is a great mixture of concepts and even some concepts that are not even explained! And please, never *ever* try to explain a concept, aplying the same concept, such as 'a force is a force that...)'

More suggestions will come. Right now I am short of time.