Atoms Rutherford experiment

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. 

In Rutherfords experiment, shown in Figure 3.16, a beam of positively charged particles, called alpha particles, was directed through an ultrathin sheet of gold foil. Since alpha particles were known to be thousands of times more massive than electrons, it was expected that the alpha-particle stream would not be impeded as it passed through the atomic pudding of gold foil. This was indeed observed to be the case—for the most part. 

The Rutherford Experiment movie (eChapter 2.4) shows alpha particles impinging on a thin gold foil. Describe what happens to the alpha particles and discuss how the results of this experiment shaped the modern view of atomic structure. 

In 1911, Ernest Rutherford s famous gold-foil experiment determined the distribution of charge and mass in an atom. Rutherford s results showed that all of an atom s positive charge and almost all of its mass are contained in an extremely small nucleus. 

The laws of chemical combination provided indirect evidence for the existence of atoms. The experiments of Thomson, Wien, and Rutherford provided direct physical evidence for the existence of the elementary particles that make up the atom. We conclude this chapter by describing an experimental method that allows us not only to image individual atoms and molecules but also to observe and control a chemical reaction at the single molecule level—a feat only dreamed of as recently as the mid-1980s. 

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. 

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. 

What was true for Nagaoka s Saturnian atom was also true, theoretically, for the atom Rutherford had found by experiment. It the atom operated by the mechanical laws of classical physics, the Newtonian laws that govern relationships within planetary systems, then Rutherford s model should not work. But his was not a merely theoretical construct. It was the result of real physical experiment. And work it clearly did. It was as stable as the ages and it bounced back alpha particles like cannon shells. 

The possibilities of Doppler-free two-photon spectroscopy for metrology and fundamental physics has been impressively demonstrated by precision measurements of the 1S-2S transition in atomic hydrogen [260-263]. Precise measurements of this one-photon forbidden transition with a very narrow natural linewidth of 1.3 Hz yield accurate values of fundamental constants and can provide stringent tests of quantum electrodynamic theory (Sect. 9.7). A comparison of the 1S-2S transition frequency with the 2S-3P frequency allows the precise determination of the Lamb shift of the 15 ground state [261], whereas the 2S Lamb shift was already measured long ago by the famous Lamb-Rutherford experiments where the RF transition between 25 1/2 and 2P /2 were observed. Because of the isotope shift the 15-25 transitions of and differ by... 

Shortly after Rutherford s conception of the nuclear atom, experiments were performed to determine the masses of individual atoms. These experiments showed that the masses of nearly all atoms were greater than could be accounted for by simply adding up the masses of all the protons and electrons that were known to be present in an atom. This fact led to the concept of the neutron, a particle with no charge but with a mass about the same as that of a proton. Because this particle has no charge, it was very difficult to detect, and the existence of the neutron was not proven experimentally until 1932. All atomic nuclei except that of the simplest hydrogen atom contain neutrons. 

Prior to Rutherford s gold-foil experiment, the mass and positively charged particles of an atom were thought to be evenly distributed throughout the volume of the atom, (a) Watch the movie of the Rutherford Experiment (eChapter 2.2), and describe how the experimental results would have been different if the earlier model had been correct, (b) What specific feature of the modern view of atomic structure was illuminated by Rutherford s experiment ... 

Describe the Rutherford experiment, and explain why the observations indicate that most of the mass of an atom is concentrated in a very small particle, the nucleus. 

Planetary model of the atom Rutherford scattering experiments... 

Dalton s atomic theory, nuclear model of the atom, planetary model of the atom, Rutherford s scattering experiment... 

The atom Rutherford chose to probe was a gold atom. Using an extremely thin gold foil, he set up an experiment in which the gold foil was suspended directly in the path of the moving alpha particles, as pictured in Figure 4.2,... 

Rutherfords experiment and the nucleus-shell-structure of the atom Radio activity... 

Charges and their behaviour Rutherfords experiment in a shoe box Rutherfords experiment The relation between nucleus and atom Diff. The life of E. Rutherford... 

In 1903, Rutherford and associates were finally able to deflect the a-rays by electric and magnetic fields, showing that these are positively charged. Measurement of the charge-to-mass ratio indicated that a-rays were of atomic dimensions. In 1908 definitive experiments showed a-rays to be doubly chaiged helium atoms, ie, helium nuclei. 

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