Rutherford’s Gold Foil ExperimentRutherford started his scientific career with much success in local schoolsleading to a scholarship to Nelson College. After achieving more academichonors at Nelson College, Rutherford moved on to Cambridge University’sCavendish laboratory. There he was lead by his mentor J. J. Thomson convincedhim to study radiation.
By 1889 Rutherford was ready to earn a living andsought a job. With Thomson’s recommendation McGill University in Montrealaccepted him as a professor of chemistry. Upon performing many experiments andfinding new discoveries at McGill university, Rutherford was rewarded the nobelprize for chemistry. In 1907 he succeded Arthur Schuster at the University ofManchester.
He began persuing alpha particles in 1908. With the help of Geigerhe found the number of alpha particles emitted per second by a gram of radium. He was also able to confirm that alpha particles cause a faint but discreteflash when striking luminescent zinc sulfide screen. These greataccomplishments are all overshadowed by Rutherford’s famous Gold Foil experimentwhich revolutionized the atomic model. This experiment was Rutherford’s most notable achievement.
It not onlydisproved Thomson’s atomic model but also paved the way for such discoveries asthe atomic bomb and nuclear power. The atomic model he concluded after thefindings of his Gold Foil experiment have yet to be disproven. The followingparagraphs will explain the significance of the Gold Foil Experiment as well ashow the experiment contradicted Thomson’s atomis model. Rutherford began his experiment with the philosophy of trying “any damfool experiment” on the chance it might work. 1 With this in mind he set out todisprove the current atomic model.
In 1909 he and his partner, Geiger, decidedErnest Marsden, a student of the University of Manchester, was ready for a realresearch project. 2 This experiment’s apparatus consisted of Polonium in a leadbox emitting alpha particles towards a gold foil. The foil was surrounded by aluminescent zinc sulfide screen to detect where the alpha particles went aftercontacting the gold atoms. Because of Thomson’s atomic model this experimentdid not seem worthwhile for it predicted all the alpha particles would gostraight through the foil. Despite however unlikely it may have seemed for thealpha particles to bounce off the gold atoms, they did.
Leaving Rutherford tosay, “It was almost as incredible as if you fired a fifteen-inch shell at apiece of tissue paper and it came back and hit you. ” Soon he came up with a newatomic model based on the results of this experiment. Nevertheless his findingsand the new atomic model was mainly ignored by the scientific community at thetime. In spite of the views of other scientists, Rutherford’s 1911 atomicmodel was backed by scientific proof of his Gold Foil Experiment.
When heapproched the experiment he respected and agreed with J. J. Thomson’s, his friendand mentor, atomic theory. This theory proposed that the electrons where evenlydistributed throughout an atom. Since an alpha paritcle is 8,000 times as heavyas an electron, one electron could not deflect an alpha particle at an obtuseangle. Applying Thomson’s model, a passing particle could not hit more than oneelctron at a time; therefore, all of the alpha particles should have passedstraight through the gold foil.
This was not the case a notable few alphaparticles reflected of the gold atoms back towards the polonium. Hence the massof an atom must be condessed in consentrated core. Otherwise the mass of thealpha particles would be greated than any part of an atom they hit. AsRutherford put it:”The alpha projectile changed course in a single encounter with a target atom. But for this to occur, the forces of electrical repulsion had to be concentrated in a region of 10-13cm whereas the atom was known to measure 10-8cm.
“He went on to say that this meant most of the atom was empty space with a smalldense core. Rutherford pondered for much time before anouncing in 1911 that hehad made a new atomic modelthis one with a condensed core (which he named the”nucleus”) and electrons orbitting this core. As stated earlier, this newatomic model was not opposed but originally ignored by most of the scientificcommunity. Rutherford’s experiment shows how scientists must never just accept thecurrent theroies and models but rather they must constently be put to new testsand experiments. Rutherford was truly one of the most successful scientists ofhis time and yet his most renowned
