Bohr s atomic model

Scientists of the nineteenth century lacked the concepts necessary to explain line spectra. Even in the first decade of the twentieth century, a suitable explanation proved elusive. This changed in 1913 when Niels Bohr, a Danish physicist and student of Rutherford, proposed a new model for the hydrogen atom. This model retained some of the features of Rutherford s model. More importantly, it was able to explain the line spectrum for hydrogen because it incorporated several new ideas about energy. As you can see in Figure 3.8, Bohr s atomic model pictures electrons in orbit around a central nucleus. Unlike Rutherford s model, however, in which electrons may move anywhere within the volume of space around the nucleus, Bohr s model imposes certain restrictions. 

If you re-read the key points of Bohr s atomic model above, you can see that he is applying the new ideas of quanta in his model. Bohr proposed that the energy that is emitted and absorbed by an atom must have specific values. The change in energy when an electron moves to higher or lower energy levels is not continuous. It is, rather, quantized. 

It was fairly straightforward to modify Bohr s model to include the idea of energy sublevels for the hydrogen spectrum and for atoms or ions with only one electron. There was a more fundamental problem, however. The model still could not explain the spectra produced by many-electron atoms. Therefore, a simple modification of Bohr s atomic model was not enough. The many-electron problem called for a new model to explain spectra of all types of atoms. However, this was not possible until another important property of matter was discovered. 

Distinguish clearly between an electron orbit, as depicted in Bohr s atomic model, and an electron orbital, as depicted in the quantum mechanical model of the atom. 

O Agree or disagree with the following statement The meaning of the quantum number n in Bohr s atomic model is identical to the meaning of the principal quantum number n in the quantum mechanical atomic model. Justify your opinion. 

Answer the following questions about Bohr s atomic model. 

It is worth noting at this point that the various scientific theories that quantitatively and mathematically formulate natural phenomena are in fact mathematical models of nature. Such, for example, are the kinetic theory of gases and rubber elasticity, Bohr s atomic model, molecular theories of polymer solutions, and even the equations of transport phenomena cited earlier in this chapter. Not unlike the engineering mathematical models, they contain simplifying assumptions. For example, the transport equations involve the assumption that matter can be viewed as a continuum and that even in fast, irreversible processes, local equilibrium can be achieved. The paramount difference between a mathematical model of a natural process and that of an engineering system is the required level of accuracy and, of course, the generality of the phenomena involved. 

The sound part of Bohr s atomic model, and its successors, appears to be the assumed quantization of electronic angular momentum and energy, as well as atomic size. Had Bohr gone one step further the proposed quantiza-... 

Bohr s atomic model was accepted in physics, with some reservation and received even less enthusiastically in chemistry, as there was no visible prospect of extending the treatment to other atoms, more complex than hydrogen. Chemical models of the era were all conditioned by the need to account for chemical interactions that bind atoms together into molecules. One of the more successful, due to Lewis, Langmuir and others, proposed a static... 

In Bohr s atomic model, electrons move around the nucleus with fixed, circular orbits. 

The reaction to Bohr s model is understandable. Bohr s atomic model was based on older laws of physics with quantum assertions added. As such, it was clearly a jumbled affair. But the model provided a pictorial explanation of the origin of spectral lines and from the model the wavelengths of the Balmer series could be calculated. The model failed for the next simplest atom, helium. Had... 

How was Bohr s atomic model able to explain the line spectrum of hydrogen ... 

The Lewis model has become so famous and has for years been used so mechanically that some of the considerations underlying it are here presented. They demonstrate how deeply Lewis was concerned with the underlying physical cause of valence rather than with a simple rule of thumb. He further points up an operational difficulty in Bohr s atomic model if it gives no information as to the electron s movement within an orbit, we have no business postulating its movement. Furthermore, electrons orbiting around a nucleus could not possibly explain directed valences. Lewis, therefore, proposed a static model, confident that theoretical chemistry would somehow, some day, confirm it ... 

What was the major contribution of Bohr s atomic model What was the major deficiency of Bohr s atomic model ... 

Bohr s atomic model was the first to successfully account for electronic properties of atoms, specifically, the interaction of atoms and light (spectroscopy). 

Planck s revolutionary idea about energy provided the basis for Einstein s explanation of the photoelectric effect in 1906 and for the Danish physicist Niels Bohr s atomic model of the hydrogen atom in 1913. Their success, in turn, lent support to Planck s theories, for which he received the Nobel Prize in physics in 1918. In the mid-1920s the combination of Planck s ideas about the particle-like nature of electromagnetic radiation and Erench physicist Louis de Broglie s hypothesis of the wavelike nature of electrons led to the formulation of quantum mechanics, which is still the accepted theory for the behavior of matter at atomic and subatomic levels. 

Bohr s atomic model> Energy for classical atomic model E = —9 a (m mass, eielectric charge, 1 angular momentum)... 

I Bohr s atomic model attributes hydrogen s emission spectrum to electrons dropping from higher-energy to lower-energy orbits. 

Explain the reason, according to Bohr s atomic model, why atomic emission spectra contain only certain frequencies of light. 

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