Download Atomic Theory - Fort Thomas Independent Schools

Important People in the
Development of Atomic Theory
Exam Review
Democritus
• The theory of
Democritus held that
everything is composed
of "atoms", which are
physically, but not
geometrically,
indivisible;
• 440 BC
Aristotle
• Disagreed with
Democritus
• Only 4 elements existfire, water, air and earth
• 350 BC
•
John Dalton
Father of Modern Atomic Theory
(1800)
Five main points of Dalton's atomic
theory
• Elements are made of extremely
small particles called atoms.
• Atoms of a given element are
identical in size, mass, and other
properties; atoms of different
elements differ in size, mass, and
other properties.
• Atoms cannot be subdivided, created,
or destroyed.
• Atoms of different elements combine
in simple whole-number ratios to
form chemical compounds.
• In chemical reactions, atoms are
combined, separated, or rearranged.
Ludwig Boltzman
• Developed the Kinetic
Theory of Matter
originally only gasses.
• As pointed out by Albert
Einstein in 1905, this
experimental evidence for
kinetic theory is generally
seen as having confirmed
the existence of atoms
and molecules.
• 1866
Dmitri Mendeleev
• Authored 1st Periodic
Table of the Elements, it
contained all the
elements known at the
time.
• 1869
James Chadwick
• In 1931, Chadwick
discovered the neutron.
• It allowed researchers to
make elements heavier
than uranium.
• For Chadwick's discovery
of the neutron in 1932, he
was awarded the Hughes
Medal of the Royal
Society in 1932 and
the Nobel Prize in
Physics in 1935.