-
Democritus’ atomic theory stated that all matter is made up small indestructible units he called atoms.
-
John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.
-
J. Plucker built one of the first cathode-ray tubes.
-
Dmitri Mendeleev created the periodic table.
-
J.J. Thomson determined the charge to mass ratio of electrons.
-
Rutherford discovered alpha, beta, and gamma rays in radiation.
-
Max Planck proposed the idea of quantization to explain how a hot, glowing object emitted light.
-
H.G.J. Moseley discovered that the number of protons in an element determines its atomic number.
-
Niels Bohr proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.
-
Louis de Broglie proposed that electrons act like waves/particles.
-
James Chadwick discovered neutrons.
