Ernest Rutherford – the Gold Foil Experiment
Ernest Rutherford was a New Zealand-born British physicist and chemist who was known as the father of nuclear physics. He studied at many colleges and universities including Havelock School, Nelson College, Canterbury College, The University of New Zealand, and The University of Cambridge. In 1908, he won the Nobel Prize in chemistry. His main contribution to physics was his invention of radio activity and the work he did with protons, neutrons, and electrons, where he concluded that an atom is mostly made up of empty space and the actual size of the atom is far smaller than the space it occupies.
Before Rutherford had done his experiment, J.J Thompson had a theory that the negative charged electrons in an atom were floating around in positive charge. Thompson’s “plum pudding model” helped show his theory. Although, in 1911, Rutherford disproved Thompson’s theory. Rutherford, with help from his students at the University of Manchester, Hans Geiger and Ernest Marsden, developed his gold foil experiment after his disapproval of the “plum pudding model”. If Thompson’s experiment was correct, then all of the alpha particles would travel right through the foil. What Rutherford did was shoot a positively charged helium particle towards a very thin layer of gold foil. He expected the positive particles to move a small distance from their path as they passed through the sea of positive charge. However, the ending result of this experiment was that the positive particles were repelled off of the foil by around 180 degrees in a very small area of the atom while the other remaining particles passed right through the atom rather than repelling. The positive particles that repelled was a very small fraction, about one in ten thousand.
With Rutherford’s experiment, it showed everyone that Thompson’s theory was incorrect, therefore giving people a different idea on atoms and how the mass of an atom is concentrated in one small area and also that an atom is mostly
Before Rutherford had done his experiment, J.J Thompson had a theory that the negative charged electrons in an atom were floating around in positive charge. Thompson’s “plum pudding model” helped show his theory. Although, in 1911, Rutherford disproved Thompson’s theory. Rutherford, with help from his students at the University of Manchester, Hans Geiger and Ernest Marsden, developed his gold foil experiment after his disapproval of the “plum pudding model”. If Thompson’s experiment was correct, then all of the alpha particles would travel right through the foil. What Rutherford did was shoot a positively charged helium particle towards a very thin layer of gold foil. He expected the positive particles to move a small distance from their path as they passed through the sea of positive charge. However, the ending result of this experiment was that the positive particles were repelled off of the foil by around 180 degrees in a very small area of the atom while the other remaining particles passed right through the atom rather than repelling. The positive particles that repelled was a very small fraction, about one in ten thousand.
With Rutherford’s experiment, it showed everyone that Thompson’s theory was incorrect, therefore giving people a different idea on atoms and how the mass of an atom is concentrated in one small area and also that an atom is mostly
References: 1. http://www.ehow.com/about_4569065_rutherfords-gold-foil-experiment.html 2. http://micro.magnet.fsu.edu/electromag/java/rutherford/ 3. http://www.daviddarling.info/encyclopedia/R/Rutherfords_experiment_and_atomic_model.html 4. http://reich-chemistry.wikispaces.com/Daniel+Varraso