In this contribution we have analyzed main ideas and principles lying at the basis of mechanical
models of molecule vibrations. We considered advantages and drawbacks of well-known models, such as the
central force model, the valence force model and Urey-Bradley's model based on purely mechanical and
volitional suggestions. A sketch of a newly developed electronic theory of molecule vibrations is also
given. It is shown that the electronic theory clarifies the physical sense of vague parameters used in
mechanical models and allows exclude excess ones. Besides of excluding excess parameters, the electronic
theory of molecule vibrations has shown that valence vibrations are not independent and connected with
deformation vibrations through electronic degrees of freedom. For example, in triatomic molecules ABA
the interaction of valence and deformation vibrations through electronic degrees of freedom leads to
changing of elastic constants and frequencies. As a consequence, the rigidity of elastic constant
ks for
symmetric longitudinal vibrations, and hence the corresponding frequency ωs respectively, is increased
whereas those, ka and ωa, for asymmetric ones are decreased in the following manner
ks=k+2kθ, ka=k-2kθ
,  .
Here k and kθ is a usual force constant of valence and deformation vibrations,
respectively, and kθ can be
expressed in terms of effective electron charges of covalent bonds. As a result, calculated frequencies
coincide practically with experimental data.
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