The machine he designed was a lightbulb with a wheel inside that had 3 cylinders of metals on it: sodium, lithium and potassium. To test this Einsteins theory, he created an experiment in light bulb.
Thomson contributed extensively to the field of chemistry by discovering the existence of electrons, developing the mass spectrometer and determining the presence. Millikan did not agree with this idea, since previously light had only been described as a wave. Define the properties of the subatomic particles including mass and charge. Summarize the evolution of atomic theory based on landmark experiments by various scientists. Dalton thought that atoms were the smallest units of matter tiny, hard spheres that could not be broken down any further. However, one of his underlying assumptions was later shown to be incorrect. Rutherfords Gold Foil Experiment and the atomic atom Elements learning objectives. Daltons ideas proved foundational to modern atomic theory. 2.2: The Discovery of Atomic Structure is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by LibreTexts. Although a mathematician and an experimental physicist by training, J. Robert Millikan Oil Drop Experiment Radioactivity. Three important kinds of radiation are particles (helium nuclei), particles (electrons traveling at high speed), and rays (similar to x-rays but higher in energy). Millikan The Man and his contributions to The Atomic Theory Robert a. Since the charge of an electron was now known due to Millikan’s research, and the charge-to-mass ratio was already known due to Thomson’s research (1. Joseph John Thomson’s contributions to science helped revolutionize the understanding of atomic structure. Millikan concluded that this value must therefore be a fundamental charge-the charge of a single electron-with his measured charges due to an excess of one electron (1 times 1.6 10 −19 C), two electrons (2 times 1.6 10 −19 C), three electrons (3 times 1.6 10 −19 C), and so on, on a given oil droplet. Looking at the charge data that Millikan gathered, you may have recognized that the charge of an oil droplet is always a multiple of a specific charge, 1.6 10 −19 C. Robert Millikan (born March 22, 1868, Morrison, Illinois, U.S.died December 19, 1953, San Marino, California) American physicist honoured with the Nobel Prize for Physics in 1923 for his study of the elementary electronic charge and the photoelectric effect. The tabulated data are examples of a few possible values. \): Millikan’s experiment measured the charge of individual oil drops. At this point, Henry Moseley believed that atomic number, the number of positive charges in the nucleus, would be a more fundamental property to use in classifying elements.