Marsden experiment

Schematic diagram of the Geiger-Marsden experiment, also known as Rutherford s gold foil experiment. [Blatt Communications.]...

The structure of the atom was revealed in 1911 as a result of Ernst Rutherford s interpretation of the 1909 Geiger-Marsden experiment (Rutherford 1911). 

Rutherford based his model on a refinement of von Lenard s electron scattering experiment carried out by Geiger and Marsden in 1909. They used u-particles, which were known to be much heavier than electrons (more than 7000 times heavier), instead of electrons as the shells . Using a thin gold foil, they observed that almost all the u-particles went through the foil undeflected, but approximately 1 in 20 000 was reflected back towards the radioactive source. Rutherford, in describing this experiment, is widely quoted as saying It was almost as if you fired a 15 inch shell at a piece of tissue paper and it came back and hit you, but the source of this quote is obscure. 

The hypothesis, experiment, and results of Rutherford s gold foil experiment. The experimental hypothesis and design owed much to the contributions of Rutherford s students, Hans Geiger (of Geiger-counter fame) and Ernest Marsden. 

The planetary model of the atom was proposed by Rutherford in 1912 following the a particle scattering experiments of Geiger and Marsden, which showed most the mass of an atom to be concentrated in a tiny positive nucleus. The orbiting of light electrons resembles the problem of planetary motion first solved by Newton. 

Hassett, D. M., Marsden, C. J., and Smith, B. J., The ammonia dimer potential energy surface Resolution of the apparent discrepancy between theory and experiment , Chem. Phys. Lett. 183, 449-456 (1991). 

He returned to England in 1908, and it was there, at Manchester University, that he and his coworkers Hans Geiger and Ernst Marsden performed the famous gold foil experiments that led to the nuclear model of the atom. Not only did he perform much important research in physics and chemistry, but he also guided the work of ten future recipients of the Nobel Prize. 

The usual preference for chromate may be shifted slightly toward dichromate by the presence of titania, although this suggestion has not been investigated much [76,102]. It is not known whether the increase in observed activity is a consequence, as seems likely, of an increase in the number of active sites, or whether the reactivity of existing sites is enhanced by the Ti-associated acidity. It seems clear, however, that the Ti-associated sites are more easily reduced, which means a faster development of polymerization rate. Experiments by Marsden [474], who used temperature programmed reduction, and also other data [103], indicate that a second, and more easily reducible, Cr(VI) species is formed by the presence of titania. Indeed, some of the behavior modification that accompanies the addition of titania is shared with other acidic supports as well. 

Ernest Marsden stndied at the University of Manchester under Ernest Rutherford and Eians Geiger. Although a physicist, he would help elucidate something of value to all chemists the internal structure of the atom. This was accomplished by observing the path of a-particles in Rutherford s famous gold foil experiment, in which it was really the human eye, pressed to a short-focus telescope for hours on end in a thoroughly darkened room, that was the detector. 

Geiger and Marsden continued to study the deflection of a-particles, and in 1913 (after observing over 100,000 scintillations at a rate of 5 to 90 per minute) correlated nuclear charge with atomic number. In 1914 and 1915 Marsden continued to study the impact of a-particles on matter these experiments led to Rutherford s 1919 fortuitous attainment of the alchemist s dream the artificial transmutation of the elements. 

Schematic diagram of the Marsden-Geiger experiment, using a-particles aimed at a thin sheet of gold foil, which demonstrated that matter was overwhelmingly empty space with dense nuclei at the centers of the atoms.

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