Quantum theory of the atom

Another consequence of the quantum theory of the atomic and nuclear systems is that no two protons, or two neutrons, can have exactly the same wave function. The practical appHcation of this rule is that only a specific number of particles can occupy any particular atomic or nuclear level. This prevents all of the electrons of the atom, or protons and neutrons in the nucleus, from deexciting to the single lowest state. 

E In the Bohr model of the atom an electron may orbit the atom s nucleus only at certain radii corresponding to certain energies. He called this the quantum theory of the atom. 

At about the same time, Bohr published his trilogy articles in which he introduced the quantum theory of the atom and obtained, by various means, the electronic configurations of many of the elements in the periodic system (Scerri, 1994b). In addition, he solidified the notion that the chemical properties of the elements were due to the orbiting electrons, which corresponds to the atomic charge of each nucleus (Bohr, 1913). Here, then, with the discoveries of Moseley and Bohr, was the solution of the tellurium/iodine inversion question. If the elements were ordered according to atomic... 

If, contrary to the order of historical development, we have discussed the quantum theory of the atom before quantum statistics, we have our reasons. In the first place, the failure of- the classical theory displays itself in atomic mechanics—for instance, in the explanation of line spectra or the diffraction of electrons—even more immediately than in the attempts to fit the law of radiation into the frame of classical physics. In the second place, it is an advantage to understand the mechanism of the individual particles and the elementary processes before proceeding to set up a system of statistics based upon the quantum idea. 

The origin and extensive application of the old quantum theory of the atom. 

At that time, the molecular theory of matter was not universally accepted. This had to wait for Einstein s 1905 explanation [32] of a study of the irregular movement of microscopic particles suspended in a liquid by the botanist Robert Brown [12] in 1828 - Brownian motion. Rutherford s 1911 paper [101] establishing the nuclear model of the atom was followed Bohr s quantum theory of the atom [8] and the flowering of Quantum Mechanics during the 1920s. Quantum ChemisUy, now mature field of scientific investigation and one of the centtal pillars of Computational Chemistty, was established in two seminal papers published in 1927 by Heitler and London [40] and Born and Qppenheimer [9]. 

But this theory was limited in its application in that it gave an exact account only of the spectrum of hydrogen, the simplest case. Atoms with more than one electron are much more complicated, since the various electrons exert influences on each other. Nevertheless, Bohr had sufficient confidence in his quantum theory of the atom to try to apply it to multielectron atoms in an approximate manner. 

A Figure 6.8 Niels Bohr (right) with Albert Einstein. Bohr (1885-1962) made major contributions to the quantum theory. From 1911 to 1913 he studied in England, working first with j. j. Thomson at Cambridge University and then with Ernest Rutherford at the University of Manchester. Ele published his quantum theory of the atom in 1914 and was awarded the Nobel Prize in physics in 1922. 

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