Gold foil

Figure Bl.19.35. Experimental nanoindentation eurves obtained with the AFM showing the loading and unloading behaviour of (a) an elastomer and highly oriented pyrolytie graphite and (b) a gold foil. (Taken from [183]. figure 4.)...

Figure 8.18 shows an X-ray photoelectron spectrum of gold foil with mercury absorbed onto the surface. Both the gold and mercury doublets result from the removal of a 4/ electron leaving /2 and /2 core states for which L = 3, S = and J = or Less than 0.1 per cent of a monolayer of mercury on a gold surface can be detected in this way. 

Figure 8.18 X-ray photoelectron spectrum of gold foil with adsorbed mercury. (Reproduced with permission, from Brundle, C. R., Roberts, M. W., Latham, D. and Yates, K., J. Electron Spectrosc., 3, 241, 1974)...

Platinum has many uses in dentistry. Pure platinum foil serves as the matrix in the constmction of fused-porcelain restorations. Platinum foil may be laminated with gold foil for cold-welded foil restorations. Platinum wire has found use as retention posts and pins in crown and bridge restorations. Heating elements and thermocouples in high-fusing porcelain furnaces are usually made of platinum or its alloys (see Platinum-GROUP metals). 

The experiment conducted by Rutherford and his co-workers involved bombarding gold foil with alpha particles, which are doubly charged helium atoms. The apparatus used in their experiment is shown in Figure 14-9. The alpha particles are produced by the radioactive decay of radium, and a narrow beam of these particles emerges from a deep hole in a block of lead. The beam of particles is directed at a thin metal foil, approximately 10,000 atoms thick. The alpha particles are delected by the light they produce when they collide with scintilltaion screens, which are zinc sulfide-covered plates much like the front of the picture tube in a television set. The screen... 

FIGURE 1.21 Davisson and Germer showed that electrons produce a diffraction pattern when reflected from a crystal G. P. Thomson, working in Aberdeen, Scotland, showed that they also produce a diffraction pattern when they pass through a very thin gold foil. The latter is shown here. G. P. Thomson was the son of J. J. Thomson, who identified the electron (Section B). Both received Nobel prizes 1.1. for showing that the electron is a particle and G. P. for showing that it is a wave. 

Binnig et al. [48] invented the atomic force microscope in 1985. Their original model of the AFM consisted of a diamond shard attached to a strip of gold foil. The diamond tip contacted the surface directly, with the inter-atomic van der Waals forces providing the interaction mechanism. Detection of the cantilever s vertical movement was done with a second tip—an STM placed above the cantilever. Today, most AFMs use a laser beam deflection system, introduced by Meyer and Amer [49], where a laser is reflected from the back of the reflective AFM lever and onto a position-sensitive detector. 

Chemical advances frequently are driven by technology. The discovery that atoms have inner structure was an outgrowth of the technology for working with radioactive materials. In Chapter 2 we describe a famous experiment in which the structure of atoms was studied by bombarding a thin gold foil with subatomic particles. A contemporary example is the use of lasers to study the details of chemical reactions. We introduce these ideas in Chapters 7 and 8. 

Schematic view of Rutherford s scattering experiment. When a beam of positively charged helium particles was shot at a thin gold foil, most of them passed through without much effect. Some, however, were reflected backward.

These results corroborated that alfalfa absorbed the Au(0) from the medium and translocated it through the vascular system. The EXAFS results (Figure 5, Table 3) showed that the Au atoms in plant samples had longer distances that the Au atoms in the tetrachloroaurate, but had equivalent distance to the Au atoms in the gold foil, which confirmed that the Au in plant samples was Au(0). 

Rutherford s experiment on alpha particle bombardment of gold foil... 

The diagram above shows the results of Rutherford s experiment in which he used a radioactive source to shoot alpha particles at a thin sheet of gold foil. Based on these results, what were Rutherford s conclusions ... 

A Rutherford s gold foil experiment that proved the existence of the nucleus... 

Read about the gold foil experiment in your textbook. Describe the plum-pudding atomic model. How did the gold foil experiment show the plumpudding model to be in error Describe the nuclear atomic model that replaced the plumpudding model. 

There was no experimental evidence for the wave nature of matter until 1927, when evidence was provided by two independent experiments. Davisson found that a diffraction pattern was obtained if electrons were scattered from a nickel surface, and Thomson found that when a beam of electrons is passed through a thin gold foil, the diffraction pattern obtained is very similar to that produced by a beam of X-rays when it passes through a metal foil. 

Rutherford s experiment demonstrated that the total positive charge in an atom is localized in a very small region of space (the nucleus). The majority of a particles simply passed through the gold foil, indicating that they did not come near a nucleus. In other words, most of the atom is empty space. The diffuse cloud of electrons (which has a size on the order of 10 8cm) did not exert enough force on the a particles to deflect them. The plum pudding model simply did not explain the observations from the experiment with a particles. 

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