Molecular shape geometrical isomerism

MO theory heteronuclear diatomic molecules Isoelectronic molecules Molecular shape and the VSEPR model Geometrical isomerism... 

Isomers that differ by their chemical constitution are constitutionally isomeric. As traditionally defined, stereoisomers are molecules with the same chemical constitution that differ with respect to the relative spatial arrangement of their constituent atoms. Since many types of flexible molecules exist whose shape rapidly change with time and that are not adequately representable by any geometric model, stereoisomers must be defined as follows, without reference to molecular geometry ... 

The vast number of structural isomers and stereoisomers is another property of diamondoids. For instance, octamantane possesses hundreds of isomers in five molecular weight classes. The octamantane class with formula C34H38 and molecular weight 446 has 18 chiral and achiral isomeric structures. Furthermore, there is unique and great geometric diversity with these isomers. For example, rod-shaped diamondoids (the shortest one of which is 1.0 nm), disc-shaped diamondoids, and screw-shaped ones (with different helical pitches and diameters) have been recognized [12]. 

Unlike dendrimers prepared by stepwise synthesis, hyperbranched polymers have diverse molecular weights, isomerism, and geometrical shapes. 

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