Molecular dipole polarizabilities are becoming of increasing importance in microscopic description of matter. polarizabilities should be used instead of "effective dielectric constant"; because in an arbitrary microscopic collection of point charges and polarizabilities, the energy and the forces depend on the nature of the charges, and on the spatial arrangement of the charges and polarizabilities. we have introduced a new molecular property, which is called Molecular compressibility, base on molecular structure, and attraction forces between nucleuses and an electron in a bond. It is shown that, this property has somthing to do with the polarizabilities of molecules.
