Wave-particle nature of matter

The miderstanding of molecular motions is necessarily based on quaiitum mechanics, the theory of microscopic physical behaviour worked out in the first quarter of the 20th century. This is because molecules are microscopic systems in which it is impossible—or at least very dangerous —to ignore the dual wave-particle nature of matter first recognized in quaiitum theory by Einstein (in the case of classical waves) and de Broglie (in the case of classical particles). 

De Broglies insight into the wave-particle nature of matter had a profound effect on scientists picture of the atom. The solution to the wave equation led to a new way of looking at the atom. The old certainties of a solid electron circling a nucleus were gone. No longer could one say the electron is here or there. An electron in an atom could be anywhere, although some locations are more likely than others. 

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