"The Atom"

  • Isaac Newton

    Isaac Newton
    Newton published an article stating his belief in the atomic nature of elements. He proposed a mechanical universe with small solid masses in motion.
  • Robert Boyle

    Robert Boyle
    Boyle published an article stating his belief in the atomic nature of elements.
  • John Dalton

    John Dalton
    Dalton stated that all matter is composed of very small particles called atoms, and that these atoms cannot be broken into smaller particles.
  • Antoine Lavoisier

    Antoine Lavoisier
    Lavoisier found that when a chemical change occurred in a closed system, the mass after a chemical change equaled the mass before the change. He proposed that matter can be changed in many ways, but it can never be created or destroyed.
  • Joseph Proust

    Joseph Proust
    Proust had observed that specific substances always contain elements in the same ratio by mass. His principle is now known as the law of definite proportions.
  • J.L. Gay-Lussac

    J.L. Gay-Lussac
    Gay-Lussac noted that, under constant conditions, the volumes of reacting gases and gaseous products are always in the ratio of small whole numbers. He discovered this while studying gas reactions at constant temperature and constant pressure.
  • Amedeo Avogadro

    Amedeo Avogadro
    Avogadro stated that equal volumes of gases, under the same conditions, always have the same number of molecules. He explained Gay-Lussac's observation using Dalton's theory.
  • Robert Millikan

    Robert Millikan
    Millikan obtained the first accurate measurement of an electron's charge. He used an oil drop apparatus like the one pictured.
  • Henri Becquerel

    Henri Becquerel
    Becquerel found that matter containing uranium exposes sealed photographic film
  • J.J. Thomson

    J.J. Thomson
    Thomson discovered electrons by doing skillful research on cathode rays. He measured the bending of the path of cathode rays to determine the ratio of an electron's charge to its mass.
  • Alber Einstein

    Alber Einstein
    Einstein explained the origin of the energy released during nuclear changes. He hypothesized that mass and energy are equal. Hence, the famous formula e=mc^2
  • Henry Moseley

    Henry Moseley
    Moseley discovered that the number of protons determines the identity of the element and the number of neutrons determines the particular isotope of the element. He found this out while studying X rays produced in X-ray tubes with anodes of different metals.
  • Lord Rutherford

    Lord Rutherford
    Rutherford predicted the existence of the third particle in an atom (the neutron).
  • Walter Bothe

    Walter Bothe
    Bothe obtained the first evidence of the third particle of an atom (the neutron).
  • James Chadwick

    James Chadwick
    Chadwick repeated Bothe's work. (He obtained evidence of the neutron.)
  • Marie and Pierre Curie

    Marie and Pierre Curie
    Using Becquerel's previous discovery, the Curies found that rays are given off by uranium and radium.