Space-filling models pentane

Attractive van der Waals forces are caused by temporary dipoles in molecules, as shown in these space filling models of pentane. 

FIGURE 2.4 Space-filling models of (a) pentane, (b) 2-methylbutane, and (c) 2,2-dlmethyl-propane. The most branched Isomer, 2,2-dlmethylpropane, has the most compact, most spherical, three-dimensional shape. 

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