• John Dalton

    John Dalton
    Gave the idea of an Atomic Theory with, based on measurable mass properties, spherical solid atoms.
  • Dmitri Mendeleev

    Dmitri Mendeleev
    Group elements with similarities into 7 groups. Found that the properties of the elements periodic functions of their atomic weights.
  • J.J. Thompson

    J.J.  Thompson
    Determined the charge of mass ratio: (e/m) of an electron=1.759 x 10 8, using a CRT.
  • Ernest Rutherford

    Ernest Rutherford
    Found that electrons were located outside the nucleus; which was dense, small, and positively charged. (not sure about specific date)
  • Niels Bohr

    Niels Bohr
    Explained that atomic structure underlies regularities of the periodic table of elements. (not sure about specific date)
  • Enrico Fermi

    Enrico Fermi
    Done the first controlled chain reaction which released energy from the atoms nucleus.