Bohr, Niels atomic orbits

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. 

In the historical Bohr (Niels Bohr, 1885-1962) model the atom is pictured as having electrons in circular orbits surrounding a small, positively charged nucleus, to which the electrons are attracted by the electrostatic Coulomb force. These orbits have... 

There was no obvious reason why Balmer s formula should be so successful. Not tmtil Niels Bohr proposed his atomic model in 1915 could fine spectra be explained in terms of electrons moving from higher-energy orbits to lower-energy ones, see also Bohr, Niels. 

Realizing that Rutherford s planetary model of the atom is incompatible with the classical Maxwell theory of radiation—which stipulates that a charged electron in circular motion will continually emit radiation and thereby lose energy, its orbit will shrink, and it will quickly spiral into the nucleus—Niels Bohr in 1913 (see Fig. 3.25) asserted that an electron in an atomic orbit simply does not radiate in other words Maxwell s theory does not apply at this level. Bohr s main contribution was to make two nonclassical assumptions. ... 

Bohr, Niels Hendrik David (1885-1962) Danish physicist. Niels Bohr was responsible for a key development in our understanding of atomic structure when he showed (1913) how the structure of the atom could be explained by imposing quantum conditions on the orbits of electrons, thus allowing only certain orbits. This theory accounted for details of the hydrogen spectrum. Bohr also contributed to nuclear physics, particularly the theory of nuclear fission. He was awarded the 1922 Nobel Prize for physics for his work on atomic theory. 

Bohr, Niels (1885-1962) A Danish theoretical physicist, Bohr introduced the concept of atomic structure, in which electrons orbit the nucleus of an atom, and laid the foundations of quantum theory, for which he was awarded the 1922 Nobel Prize in Physics. He later identified U-235, an isotope of uranium that produces slow fission. During World War II, after escaping from Nazi-occupied Denmark, he worked as consultant to the Manhattan Project Following the war, he returned to Denmark and became a staunch advocate for the nondestructive uses of atomic energy. 

He also proposed that electrons travel in orbits around the nucleus. His own student and co-worker Niels Bohr (born in Copenhagen in 1885) criticized Rutherford s model. In papers pubHshed in 1913 he expressed what has since then been known as Bohr s atomic model. Making use of the quantum theory and Planck s constant he postulated that electrons could only be situated in certain orbits or quantum levels. 

Bohr, Niels (1885-1962) Danish physicist who formulated the Bohr model for the atom. In this model, electrons orbit the nucleus, much like planets orbit the sun. boiling point The temperature at which the liquid and gaseous forms of a substance coexist, bonding pair electrons The electrons between two atoms in a Lewis structure. 

Niels Bohr used the notion of atomic orbits in his theory of the hydrogen atom and even gave an approximate explanation for the form of the periodic table of the elements, by appealing to electron orbits in many-electron atoms (Scerri 1997). However, he himself soon realized that such electron orbits in atoms larger than hydrogen would have to be regarded as only useful approximations. 

In 1913 Niels Bohr proposed a system of rules that defined a specific set of discrete orbits for the electrons of an atom with a given atomic number. These rules required the electrons to exist only in these orbits, so that they did not radiate energy continuously as in classical electromagnetism. This model was extended first by Sommerfeld and then by Goudsmit and Uhlenbeck. In 1925 Heisenberg, and in 1926 Schrn dinger, proposed a matrix or wave mechanics theory that has developed into quantum mechanics, in which all of these properties are included. In this theory the state of the electron is described by a wave function from which the electron s properties can be deduced. 

Figure 5. Niels Bohr came up with the idea that the energy of orbiting electrons would be in discrete amounts, or quanta. This enabled him to successfully describe the hydrogen atom, with its single electron, In developing the remainder of his first table of electron configurations, however, Bohr clearly relied on chemical properties, rather than quantum theory, to assign electrons to shells. In this segment of his configuration table, one can see that Bohr adjusted the number of electrons in nitrogen s inner shell in order to make the outer shell, or the reactive shell, reflect the element s known trivalency.

In an early model of the hydrogen atom proposed by Niels Bohr, the electron traveled in a circular orbit of radius uncertainty principle rules out this model. 

Particularly spectra and quantum theory seemed to indicate an order. A planetary model almost suggested itself, but according to classical physics, the moving electrons should emit energy and consequently collapse into the nucleus. The 28-year-old Niels Bohr ignored this principle and postulated that the electrons in these orbits were "out of law". This clearly meant that classical physics could not describe or explain the properties of the atoms. The framework of physical theory came crashing down. Fundamentally new models had to be developed.1... 

The first plausible theory of the electronic structure of the atom was proposed in 1914 by Niels Bohr (1885-1962), a Danish physicist. In order to explain the hydrogen spectrum (Fig. 17-1), he suggested that in each hydrogen atom, the electron revolves about the nucleus in one of several possible circular orbits, each having a definite radius corresponding to a definite energy for the electron. An electron in the orbit closest to the nucleus should have the lowest energy. With the... 

Following Rutherford s experiments in 1911, Niels Bohr proposed in 1913 a dynamic model of the hydrogen atom that was based on certain assumptions. The first of these assumptions was that there were certain "allowed" orbits in which the electron could move without radiating electromagnetic energy. Further, these were orbits in which the angular momentum of the electron (which for a rotating object is expressed as mvr) is a multiple of h/2ir (which is also written as fi),... 

The chemical properties of an element are functions of the number and distribution of its electrons around the nucleus. In 1913, Niels Bohr devised a model for the atom that successfully explained why atomic spectra consist of discrete lines, not only in X-rays, as discussed above, but also in visible light. Building on the ideas of quantum mechanics, he postulated that the angular momentum of an orbiting electron can only have certain fixed values. If so, then the orbital energy associated with any electron cannot vary continuously, but can only have discrete quantum values. He described a series of spherical shells at fixed... 

The starting point of the creation of the theory of the many-electron atom was the idea of Niels Bohr [1] to consider each electron of an atom as orbiting in a stationary state in the field, created by the charge of the nucleus and the rest of the electrons of an atom. This idea is several years older than quantum mechanics itself. It allows one to construct an approximate wave function of the whole atom with the help of one-electron wave functions. They may be found by accounting for the approximate states of the passive electrons, in other words, the states of all electrons must be consistent. This is the essence of the self-consistent field approximation (Hartree-Fock method), widely used in the theory of many-body systems, particularly of many-electron atoms and ions. There are many methods of accounting more or less accurately for this consistency, usually named by correlation effects, and of obtaining more accurate theoretical data on atomic structure. 

With the particlelike nature of energy and the wavelike nature of matter now established, let s return to the problem of atomic structure. Several models of atomic structure were proposed in the late nineteenth and early twentieth centuries. A model proposed in 1914 by the Danish physicist Niels Bohr (1885-1962), for example, described the hydrogen atom as a nucleus with an electron circling around it, much as a planet orbits the sun. Furthermore, said Bohr, only certain specific orbits corresponding to certain specific energy levels for the electron are available. The Bohr model was extremely important historically because of its conclusion that electrons have only specific energy levels available to them, but the model fails for atoms with more than one electron. 

According to an early theory about the atom, the atom looks like a mini solar system. The nucleus of the atom would be the Sun and the electrons are the orbiting planets. This model of the atom is called the Bohr model. It is named for the Danish physicist, Niels Bohr, who proposed electron shells in 1913. The Bohr model is very useful for understanding how atoms work, but it does not answer some questions about the behavior of all atoms. 

Figure 2.2 The Bohr atom was proposed by Niels Bohr. He believed that electrons moved around the nucleus similar to the way planets orbit the Sun.

Niels Bohr incorporated Planck s quantum concept into Rutherford s model of the atom in 1913 to explain the discrete frequencies of radiation emitted and absorbed by atoms with one electron (H, He+, and Li2+). This electron is attracted to the positive nucleus and is closest to the nucleus at the ground state of the atom. When the electron absorbs energy, it moves into an orbit further from the nucleus and the atom is said to be in an electronically excited state. If sufficient energy is absorbed, the electron separates from the nucleus entirely, and the atom is ionized ... 

By now, it was becoming clear that there was a connection between electrons in bodies, the radiant energy emitted by those bodies, and the distribution of that energy in the spectrum. But a more detailed theory with more information was needed. Rutherford had proposed an atom modeled on the solar system, with electrons orbiting around a positive nucleus and a lot of empty space between the electrons and the nucleus. In 1913 the Danish physicist Niels Bohr (1885-1962), who worked with Rutherford for four years and on his return to Copenhagen made Denmark a world center of theoretical physics, published one of the twentieth century s most important papers. He applied Planck s equation and the notion of quantization of energy to Rutherford s... 

In 1913, the Danish physicist Niels Bohr developed a model of the atom that explained the hydrogen emission spectrum. In Bohr s model, electrons orbit the nucleus in the same way that Earth orbits the Sun, as shown in Figure D.2. The following three points of Bohr s theory help to explain hydrogen s emission spectrum. 

Niels Bohr s planetary model of the hydrogen atom—in which a nucleus is surrounded by orbits of electrons—resembles the solar system. Electrons could be excited by quanta of energy and move to an outer orbit (excited level). They could also emit radiation when falling to their original orbit (ground state). Basic components of the Bohr model include the following ... 

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