Unit 5: Periodic Table

1
Unit 5 Periodic Table

• Part 1 A Very Brief History of the
• Periodic Table

2
Dmitri Mendeleev

• Russian Chemist
• In 1869, he published the
• first periodic table.
• He organized the elements in a way that would
  help his students learn them more easily.
• He made a card game with the information known
  about each element listed on separate cards.
  They could then be arranged by the properties the
  elements had in common.

3

• Mendeleev settled on an organization of elements
  that was based on the masses of the elements.
• Mendeleev found that when the elements were
  arranged in order of atomic mass, many physical
  and chemical properties of the elements followed
  repeating patterns.

4

• Worked for most elements, but not all.
• Three pairs of elements had to be switched, but
  Mendeleev thought these masses were measured
  incorrectly.

5
Ekasilicon

• Mendeleev was able to accurately predict the
  existence of elements not yet discovered. These
  showed up as gaps in his periodic table.
• One such element gap, Mendeleev called
  ekasilicon. He predicted its mass, density,
  melting point and color based on its location in
  the periodic table.
• Fifteen years after this prediction, a new
  element was discovered in Germany and given the
  name Germanium. Its properties matched the
  properties of ekasilicon.

6

• H.G.J Moseley worked in Rutherfords lab.
• Found that metals produce X-rays when bombarded
  with energetic electrons and that the frequencies
  differed for each metal. These frequencies, came
  from differences in a fundamental property of
  each element the amount of positive charge.
• The amount of positive charge the number of
  protons the atomic number.

7
Discovery Video
8
Modern Periodic Law

• When the elements are arranged in order of
  increasing atomic number, their physical and
  chemical properties show a periodic, repeating
  pattern.

9
Periodic Table Arrangement

• Periods the horizontal rows of elements.
• The modern periodic table has 7 periods.
• The period tells the number of energy levels
  used. This is the Principal Quantum Number.
• n1 or n2, etc., in the Bohr Model

10
Periodic Table Arrangement

• Groups the vertical columns of elements.
• The modern periodic table has 18 groups.
• The A groups tell the number of valence
  electrons.
• Groups are sometimes referred to as families.