Bell work

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Bell work
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The Periodic Table
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• Modern Chemistry Chapter 5.1 pg. 133-136

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Origin of the Periodic Table

• most of the elements were discovered during the
  1800's
• Johann Dobereiner, a German chemist, and the
  Englishman John Newlands were the first who
  attempted to find similarities between the
  elements
• they noticed that there were similarities
  between atomic masses and chemical properties of
  the elements

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• German chemist, Lothar Meyer, developed this
  idea, he noticed that when you arranged the known
  elements in increasing atomic masses, certain
  patterns of repetition of properties became
  evident
• the Russian chemist, Dimitri Mendeleev, was the
  first to publish a system of classifying
  elements, which became the basis for what we use
  today
• 1869, he developed a table of elements that was
  extremely well planned and detailed

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• Mendeleevs Periodic Table

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• He arranged the elements in order of their
  atomic masses
• in his earlier, table he placed elements with
  similar properties in horizontal rows
• if no known element had the expected prop to
  fit a particular place in the table he left the
  place empty
• he assumed these placed were elements which had
  not been discovered yet- so from the pattern that
  he saw he was able to predict the properties of
  these unknown elements with uncanny accuracy

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• Q1 Give an example of Mendeleev predictions?
  for Germanium- Ekasilicon
• Property Predicted Observed
• atm mass 72 72.59
• Density 5.5 5.3
• form of oxide EsO2 GeO2
• D of oxide 4.7 4.2
• Form of Cl EsCl4 GeCl4
• D of Cl 1.9 1.8

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• Mendeleev's table was called the periodic table
  because it was based on his Periodic Law
• Q2 State Mendeleev's Periodic Law
• when you order the elements according to
  increasing atomic masses, ever-so-often(periodical
  ly) the physical and chemical properties will
  repeat themselves

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• -Mendeleev also realized that there were some
  problems with the chart. Look at Iodine and
  Tellurium
• Q4 What is the problem with I-Te? How did he
  solve it?

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• in 1914, Henry Mosely, an English physicist,
  was able to do several experiment that revealed
  that the single most important attribute of any
  element was its atomic number or number of
  protons
• he suggested that the Periodic Table should be
  arranged according to increasing atomic number
  instead of mass

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• Q5 How did this solve the I-Te problem?
• Mosely helped to frame the new Periodic Law
• Q6 State the Modern Periodic Law

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Reading the Periodic Law

• Q7 Write down some observations that can be
  made concerning the Modern Periodic Table

Periodic Table divided into 7 rows called periods