Bent's TSM (e.g. J.Chem.Ed.,40(1963)446,523) is a qualitative, arbitrary interpretation of the quantitative Kimball model. TSM cannot be falisified, it is not science. To argue within the quantitative model of Kimball: "Free cloud" means, the clouds get their size and go where they must according to scientific laws: the quantum mechanical kinetic energy and Pauli's exclusion principle, confined by the electrostatic interactions between clouds, clouds and nuclei, and nuclei-nuclei, which define the molecular structure. The requirement of "tangent clouds" is foreign to Kimball's model. It is an arbitrary constraint which leads to a destabilization of the computed molecule and to a violation of the Hellmann-Feynman theorem, which postulates that the vectorsum of all forces any nucleus of the (stationary - vibrationless) molecule is exposed to must vanish. Bent's molecules are mostly not in equilibrium and have huge forces (e.g.
ethene) driving to change the structure.
That means: TSM is Bent's "model" (phantasy?), not Kimball's (G.F.Neumark's thesis, loc.cit p.30: "The outer clouds touch the central one, but not necessarily each other."). Because Bent's TSM has no quantitative boundary, no energy minimum nor vanishing forces like Kimball's model, cloud tangency creates the metric for the structure of a molecule. This is an unphysical and unchemical assumption! What action in our Universe creates the unpenetrable tangency? witchcraft? a new field? what defines the radii of the tangent spheres?- Where have the editors of the Journal of Chemical Education been between 1963 and 1986 to publish such trash?
For detailed study continue to Springs & bolts and Ethene
I still remember, how furious I became while reading Bent's first paper. My students and myself had already been studying Kimball's quantitative model for more than a year, the first publication had been drafted, and now this! Bent has been the first gravedigger *) of Kimballs model by corrupting it before the scientific discourse about its merits had taken place. The qualitative interpretation, with arbitrary features added, withdrew Kimballs model from a serious evaluation process as scientific object, which, therefore, has never happened! This paved the way to the styrofoam, plastilline and artwork "Kimball" or "Kugelwolken" varieties of science teachers who have not understood the model.-
This sad history has disgusted me so much, that I needed more than 50 years to present here a mouthful of our early endeavor (partially from three drafts of unpublished work 1961-64) - for your amusement!
*) On similar footing was the "Chemical Bond Approach Committee", Chemistry Vol.I (2nd ed.) 1960, Editor in Chief L.E.Strong. Chapters IV and VI had so many qualitative and quantitative errors that the strong arm of George Pimentel, entering the "CHEM study" program, was welcome to stop the nonsense!