Periodic Table Timeline
Category: Altro
è stato aggiornato: 14 dic 2017
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Created byKimira B
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More than 60 elements had been discovered.A group of chemists assembled
at the First International
Congress of Chemists in
Karlsruhe, Germany to settle
the issue of atomic
mass as well as
some other matters that
were making communication difficult.
Stainslao Cannizzaro presented a
convincing method for accurately
measuring the relative masses
of atoms. His method
enabled chemists to agree
on standard values for
atomic mass and initiated
a search for relationships
between atomic mass and
other properties of the
elements.Dmitri Mendeleev publishes his
first periodic table he
made that was arranged
in order of increasing
atomic mass, the similarities
of the elements appeared
at regular intervals in
a periodic pattern. There
were several empty spaces
in his table.Mendeleev predicted the existence
and properties of the
elements that would fill
three of the spaces.All three missing elements
are discovered
(Scandium, Gallium, Germanium)Helium is discoveredJohn Williams Strutt and
Sir WIlliam Ramsay discover
ArgonRamsay discovered two more
noble gases, Krypton and
XenonFriedrich Ernest Dorn discovered
the final noble gas
Radon.Early 1900s: Lanthanides were
finally understood. Actinides were
discovered.Henry Moseley worked with
Ernest Rutherford and while
analyzing different metals, realized
an unrecognized pattern. Moseley’s
work led to both
the modern definition of
atomic number and the
recognition that atomic number
is the basis for
the organization of the
periodic table. This conclusion
led to Mendeleev’s table
to undergo extensive change.
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