Nucleus Rutherford experiment

In 1911, the British physicist and Nobel laureate Ernest Rutherford (1871-1937) published the article The Scattering of Alpha and Beta Particles by Matter and the Structure of the Atom in Philosophical Magazine. In this article, Rutherford reported the results of an experiment that demonstrated that the protons and electrons in atoms are not distributed homogeneously. Instead, the protons are concentrated in a relatively tiny region Rutherford called the nucleus (from the Latin, meaning kernel ). The electrons are extranuclear electrons are located in a relatively much larger volume of space surrounding the nucleus. Rutherford s discovery of the nucleus was immediately accepted within the scientific community. However, the relationship, if any, between atomic structure and properties was still unclear. 

Hg. 3.1 Explanation of the Rutherford experiment. The path of the alpha particles Is shown by arrows. Only If an alpha particle makes a direct hit on a nucleus does It suffer a large deflection. 

FIG. 23. Rutherford experiment led to concept of nucleus and opened the door to modern nuclear physics. Alpha particles emitted from radioactive source were deflected when passing through gold foil. Amount of deflection was recorded when particles struck the photographic plate. 

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. 

The Rutherford experiment was performed and its conclusions reached before protons and neutrons were discovered. When they were found, why was it believed that they were in the nucleus... 

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... 

Schematic drawing of an atom, showing a central, positive nucleus surrounded by a cloud of electrons. This model of the atom is consistent with the results of Rutherford s scattering experiments.

Recall from Chapter 2 what Rutherford s scattering experiment demonstrated. Every atom contains a tiny central core where all the positive charge and most of the mass are concentrated. Subsequent experiments showed that while the masses of nuclei can have various values, the mass of every nucleus is at least 1800 times larger than the mass of the electron. Thus, more than 99.9% of the mass of an atom is contained in its nucleus. 

The volume of an atom is determined by the size of its electron cloud. Example demonstrates that atomic dimensions are a little over 10 m, whereas Rutherford s experiments showed that nuclear dimensions are only about 10 m. This is 100,000 times smaller than atomic dimensions, so the nucleus is buried deep within the electron cloud. If an atom were the size of a sports stadium, its nucleus would be the size of a pea. Figure 7 1 shows a schematic view of two atoms with their electron clouds in contact with each other. 

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

Chemists were not able to use their methods to determine the structure of the atom. The discovery of radioactivity by Henri Becquerel and the work of Marie and Pierre Curie showed, however, that heavy elements were not stable. The earlier postulate of their indivisibility could no longer be maintained. In 1906 Ernest Rutherford made the next horrorif-ic revelation his scattering experiments showed that the atom was almost empty. A tiny nuclear mass was circled by electrons at a large distance. For comparison, if the nucleus were the size of a cherry pit and were placed in the center of a football field, the electrons would be circulating in the back rows of the stadium. If the nucleus were the size of a football, the first electrons would be circling it at a distance of one kilometer. Between them would be absolute emptiness. 

Sir Ernest Rutherford (1871-1937 Nobel Prize for chemistry 1908, which as a physicist he puzzled over) was a brilliant experimentalist endowed with an equal genius of being able to interpret the results. He recognized three types of radiation (alpha, beta, and gamma). He used scattering experiments with alpha radiation, which consists of helium nuclei, to prove that the atom is almost empty. The diameter of the atomic nucleus is about 10 000 times smaller than the atom itself. Furthermore, he proved that atoms are not indivisible and that in addition to protons, there must also be neutrons present in their nucleus. With Niels Bohr he developed the core-shell model of the atom. 

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. 

Now Rutherford has proved that the most important constituent of an atom is its central positively charge nucleus, and van den Broek has put forward the view that the charge carried by this nucleus is in all cases an integral multiple of the charge on the hydrogen nucleus. There is every reason to suppose that the integer which controls the X-ray spectrum is the same as the number of electrical units in the nucleus, and these experiments therefore give... 

Rutherford s discovery of the atomic nucleus was his greatest contribution to physics and it established him as the leading experimental physicist of his day. However, it was only a beginning, and many questions about the atom remained unanswered. As yet nothing was known about electron orbits or about the relationship between the structure of the atom and the periodic table. Before Rutherford performed his experiments, it was thought that the atom was understood. Now it was apparent that much remained to be learned. But then great discoveries in physics seem always to suggest new questions and open up new lines of research. The more that is known, the better the picture scientists have of what remains unknown. 

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