Atoms Rutherford model

In the early part of the twentieth century, then, a simple model of atomic structure became accepted, now known as the Rutherford nuclear model of the atom, or, subsequently, the Bohr-Rutherford model. This supposed that most of the mass of the atom is concentrated in the nucleus, which consists of protons (positively charged particles) and neutrons (electrically neutral particles, of approximately the same mass). The number of protons in the nucleus is called the atomic number, which essentially defines the nature of... 

Can the Rutherford model of the atom explain the emission spectra of elements ... 

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. 

The Bohr model of the atom took shape in 1913. Niels Bohr (1885-1962), a Danish physicist, started with the classic Rutherford model and applied a new theory of quantum mechanics to develop a new model that is still in use, but with many enhancements. His assumptions are based on several aspects of quantum theory. One assumption is that light is emitted in tiny bunches (packets) of energy call photons (quanta of light energy). 

In 1910 Rutherford wrote to a friend, I think I can devise an atom much superior to J.J. s, for the explanation of and stoppage of alpha and beta particles, and at the same time I think it will fit in extraordinary well with the experimental numbers. Rather than devise a model of the atom based on theoretical ideas as Thomson had done, Rutherford intended to probe atomic structure by bombarding atoms with particles ejected from radioactive atoms. Rutherford felt that experimental physics was the only real physics and that by performing experiments he could gain greater insight into atomic structure than Thomson had been able to get using only theory. 

The 3rd Solvay Conference in Physics took place in 1921, after a long interruption due to the First World War. Its theme was Atoms and Electrons. 20 It was centered on the Rutherford model of the atom and Niels Bohr s atomic theory. Bohr, however, was not able to attend the conference because of illness. 

Just as the Rutherford model of the atom developed in 1911 was scientifically startling with its revelation of the atom as mostly empty space, so was the Bohr model of the atom introduced in 1913 with its definition of the location of the electron within the atom. As Bohr and others realized that the atomic spectrum of each element is caused by electrons changing energy levels, a different picture of the atom emerged. The new picture of the atom had electrons at various energy levels within the empty space of Rutherford s model (Figure 8.6). This space can still be said to be empty because the mass of the electrons is extraordinarily small in comparison with that of the whole atom. 

The Rutherford model of the atom, in turn, was replaced only two years later by a model developed by Niels Bohr, a Danish physicist. The Bohr model, which is shown in Figure 16, describes electrons in terms of their energy levels. 

Rutherford proposed a model of the atom in which the charge on the nucleus was +Ze, with Z electrons surrounding the nucleus out to a distance of about 10 ° m (0.1 nm). The Rutherford model for a gold atom has 79 electrons (each with a charge of —le) arranged about a nucleus of charge +79e. The electrons occupy nearly the entire volume of the atom, whereas nearly all its mass is concentrated in the nucleus this model is often called the planetary model. ... 

The Rutherford model has become the universally accepted picture of the structure of the atom. The properties of a given chemical element arise from the charge +Ze on its nucleus and the presence of Z electrons around the nucleus. This integer Z is called the atomic number of the element. Atomic numbers are given on the inside back cover of this book. 

Rutherford was able to determine the magnitudes of the positive charges on the atomic nuclei. The pictme of atomic structure that he developed is called the Rutherford model of the atom. 

The Rutherford model of the atom is consistent with the evidence presented so far, but it has some serious limitations. It does not answer such important questions as Why do different elements have such different chemical and physical properties Why does chemical bonding occur at all IVhy does each element form compounds with characteristic formulas How can atoms of different elements give off or absorb light only of characteristic colors (as was known long before 1900) ... 

AtomStru Structure of the Atom - Dalton, Thompson and Rutherford Models - Atomic Number - Atomic Weights - Isotopes. 

In 1909, a team of scientists led by Ernest Rutherford in England carried out the first of several important experiments that revealed an arrangement far different from the cookie-dough model of the atom. Rutherford s experimental setup is shown in Figure 2.9. 

O What caused Rutherford to propose a revised model of the atom How is the Rutherford model different from the previous models ... 

Rutherford s model of the atom Rutherford concluded that the plum pudding model was incorrect because it could not explain the results of the gold foil experiment. Considering the properties of the alpha particles and the electrons, and the frequency of the deflections, he calculated that an atom consisted mostly of empty space through which the electrons move. He also concluded that almost all of the atom s positive charge and almost all of its mass were contained in a tiny, dense region in the center of the atom, which he called the nucleus. 

TheoreticThomson model (a mix of peirticles with positive md negative charges), B— the Rutherford model (a positive nucleus surroimded by electrons), C—the Bohr model (stating that electrons follow defined orbits around a nucleus), [Pg.14]

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