1834 Michael Faraday÷electrolysis experiments suggested
electrical nature of
matter.
1895 Wilhelm Roentgen÷discovered X-rays when cathode rays
strike the anode.
1896 Henri Becquerel÷discovered ãuranic raysä and radioactivity.
1896 Marie (Marya Sklodowska) and Pierre Curie÷discovered
that radiation is
a property of the atom, and not due to chemical reaction. (Marie named
this
property radioactivity.)
1897 Joseph J. Thomson÷discovered the electron through
Crookes tube
experiments.
1898 Marie and Pierre Curie÷discovered the radioactive
elements polonium and
radium.
1899 Ernest Rutherford÷discovered alpha and beta particles.
1900 Paul Villard÷discovered gamma rays.
1903 Ernest Rutherford and Frederick Soddy÷established
the laws of radioactive
decay and transformation.
1910 Frederick Soddy÷proposed the isotope concept to
explain the existence of
more than one atomic weight of radioelements.
1911 Ernest Rutherford÷used alpha particles to explore
gold foil; discovered the
nucleus and the proton; proposed the nuclear theory of the atom.
1919 Ernest Rutherford÷announced the first artificial
transmutation of atoms.
1932 James Chadwick÷discovered the neutron by alpha
particle bombardment
of Beryllium.
1934 Frederic Joliot and Irene Joliot Curie÷produced
the first artificial
radioisotope.
1938 Otto Hahn, Fritz Strassmann, Lise Meitner, and
Otto Frisch÷discovered
nuclear fission of uranium-235 by neutron bombardment.
1940 Edwin M. McMillan and Philip H. Abelson÷discovered
the first transuranium
element, neptunium, by neutron irradiation of uranium in a cyclotron.
1941 Glenn T. Seaborg, Edwin M. McMillan, Joseph W.
Kennedy and Arthur C.
Wahl÷announced discovery of plutonium from beta particle emission of
neptunium.
1942 Enrico Fermi÷produced the first nuclear fission
chain-reaction.
1944 Glenn T. Seaborg÷proposed a new format for the
periodic table to show that
a new actinide series of 14 elements would fall below and be analogous
to the
14 lanthanide-series elements.
1964 Murray Gell-Mann hypothesized that quarks are
the fundamental particles
that make up all known subatomic particles except leptons.
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TABLE OF CONTENTS | TOPIC OVERVIEW | CONCEPT/SKILLS DEVELOPMENT | LINKS/CONNECTIONS | EXTENSIONS | ![]() |
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