Implications of Bohrs theory

Between 1912 and 1925, Bohr s theory of the atom gave rise to a conceptual framework for the study of matter on many fronts. Applying the theory to predict the energy levels and therefore the emission frequencies of atoms more complicated than hydrogen—say, helium with two electrons, lithium with three, and so on— led to the concept of electronic shells about the nucleus, the outer shell less tightly bound, and it is these outer-shell electrons that determine the element s spectrum. It should be pointed out that the theory was not fully successful in predicting the spectral lines of the elements that are more complicated than hydrogen. 

Furthermore, the concept of electronic shells initiated the modern atomic theory of chemical reactions. It is now well accepted that the electrons in the outer shells, transferring from one atom to another or being shared by two atoms, provide the machinery for chemical reactions and the binding of atoms to form molecules. 

Despite its successes, Bohr s theory did not resolve the fundamental issues that lie at the heart of the quantum theory of Planck and Einstein What is behind the quantization of oscillators and atoms What happens when a system changes its state, resulting in the creation of a photon How can the generated photon behave like a particle under certain conditions and like a wave under other conditions  

Laser technology is one of those rare instances in scientific research, such as the development of nylon, atomic fission, or genetic engineering, where important technologies have sprung directly from scientific theory. 

Light Fantastic, p. 232, Penguin Books, New York (1981). 

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