![]() ![]() Thomson’s first graduate student at the Cavendish Laboratory. He was released from this task by a scholarship to Cambridge University, where he became J. Education and Early Careerīorn on a farm in New Zealand, the fourth of 12 children, Rutherford completed a degree at the University of New Zealand and began teaching unruly schoolboys. Rutherford on the New Zealand 100-dollar banknote. ![]() Most important, he postulated the nuclear structure of the atom: experiments done in Rutherford’s laboratory showed that when alpha particles are fired into gas atoms, a few are violently deflected, which implies a dense, positively charged central region containing most of the atomic mass. He discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei. A Series of DiscoveriesĪ consummate experimentalist, Rutherford was responsible for a remarkable series of discoveries in the fields of radioactivity and nuclear physics. ![]() He received the Nobel Prize in Chemistry in 1908. The nucleus is the tiny, dense, central core of the atom and is composed of protons and neutrons.Ernest Rutherford (1871–1937) postulated the nuclear structure of the atom, discovered alpha and beta rays, and proposed the laws of radioactive decay. He concluded that all of the positive charge and the majority of the mass of the atom must be concentrated in a very small space in the atom's interior, which he called the nucleus. In contrast, the particles that were highly deflected must have experienced a tremendously powerful force within the atom. Because the vast majority of the alpha particles had passed through the gold, he reasoned that most of the atom was empty space. Rutherford needed to come up with an entirely new model of the atom in order to explain his results. In a famous quote, Rutherford exclaimed that it was "as if you had fired a 15-inch shell at a piece of tissue and it came back and hit you." No prior knowledge had prepared them for this discovery. Some were even redirected back toward the source. Surprisingly, while most of the alpha particles were indeed not deflected, a very small percentage (about 1 in 8000 particles) bounced off the gold foil at very large angles. (Credit: (A) Christopher Auyeung (B) User:Fastfission/Wikimedia Commons Source: (A) CK-12 Foundation (B) (opens in new window) License: (A) CC BY-NC 3.0(opens in new window) (B) Public Domain)Īccording to the accepted atomic model-in which an atom's mass and charge are uniformly distributed throughout the atom-the scientists hypothesized that all of the alpha particles would pass through the gold foil with only a slight deflection, or none at all. Rutherford found that a small percentage of alpha particles were deflected at large angles, which could be explained by an atom with a very small, dense, positively-charged nucleus at its center (bottom). (B) According to the plum pudding model (top), all of the alpha particles should have passed through the gold foil with little or no deflection. \) : (A) The experimental setup for Rutherford's gold foil experiment: A radioactive element that emitted alpha particles was directed toward a thin sheet of gold foil that was surrounded by a screen which would allow detection of the deflected particles. ![]()
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