Periodic Table

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Periodic Table
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History

• The modern periodic table is based primarily
• on the work of the Russian chemist Dmitri
• Voinovich Mendeleev (1834-1907) and the
• German physicist Julius Lothar Meyer
• (1830-1895). Working independently, both
• scientists developed similar periodic tables
• in 1869. Mendeleev receives the credit
• because he managed to publish his work

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• The table Mendeleev developed is very
• similar to the one we use today. He listed
• elements by similarities and their atomic
• Weight. It was not until the beginning of the
• 20th century, with the knowledge gained
• about the structure of the atom, that the
• Correct way of ordering the elements was
• discovered and the modern periodic table was
• created

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• April 1897, Joseph John Thompson
• (physicist) discovered the electron
• 1911, Ernest Rutherford (Physicist) discovered
  the nucleus and in 1920, the Proton.
• 1932, Ernest Rutherford (physicist) discovered
  the neutron

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• Henry Moseley (physicist) discovered every
  element had a different number of protons in the
  nucleus and this became known as the atomic
  number.
• The unique properties of each of the chemical
  elements are determined by their number of
  neutrons, protons, and electrons. Besides
  determining the properties of a pure chemical
  element, the neutron, proton, and electron
  content of its atoms also determines its behavior
  in relation to other chemical elements

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The Modern Periodic Table

• The Modern statement of the periodic law is that
  the chemical and physical properties the elements
  vary in a periodic way with their atomic numbers
• The periodic table is organized like a big grid.
  The Elements are placed in specific places
  because of the way they look and act. The
  periodic table has rows and columns and they each
  mean something different

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Periods

• When you look at the picture below, you can see
  that the rows are different colors. Even though
  they skip some squares in between, all of the
  rows go left to right. When you look at a
  periodic table each of the rows are considered to
  be different PERIODS.

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Periods
4 4 4
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• In the periodic table, elements have something in
  common if they are in the same row. All of the
  elements in the second row (the second period)
  have two shells for their electrons. It goes down
  the periodic table like that.

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The Groups

• The periodic table haw a special name for its
  columns too. When a column goes from top to
  bottom, its called a GROUP. The elements in a
  group have the same number of electrons in the
  outer shell.

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Groups
66666666666
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• So, every element in the first column (group one)
  has one electron is its outer shell. Every
  element on the second column (group two) has two
  electrons in the outer shell.

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Hydrogen

• Hydrogen is special. Hydrogen can have the
  electrons of two groups, one and seven. To
  scientists, Hydrogen is sometimes missing an
  electron. And sometimes it has an extra. Helium
  is different. It can only have two electrons in
  its outer shell, but it still gets grouped with
  elements that have eight.

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• The elements in between, with the grey color, are
  called Transition elements. They are not in our
  main group.