How the Elements Were Won

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How the Elements Were Won

• Your Guide to the History of the Periodic Table
• and the Periodic Law

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History of the Periodic Table

• By the late-1800s, many elements in the earths
  crust, oceans, and air had been discovered
• As the number of known elements increased,
  scientists began to devise ways to classify the
  elements in useful ways

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Dmitri Mendeleev Father of the Periodic Table

• Mendeleev is considered the father of the
  Periodic Table
• 1868 - Arranged the known elements in order of
  increasing atomic mass
• Noticed that similar properties of elements
  appeared at regular intervals
• Left spaces for undiscovered elements!

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Howd He Do That?Mendeleev and Periodic
Solitaire

• Mendeleev began organizing the known elements by
  first writing everything that was
  known about an element on index cards
• He began placing the elements in order of
  increasing atomic weight
• groups began to form that had similar properties
• Where gaps occurred, Mendeleev predicted the
  existence of new elements and their properties
• Mendeleev was right three of the elements he
  predicted were discovered in his lifetime
• But, there were some inconsistencies in
  Mendeleevs arrangement

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Mendeleevs Original TableHow is it different
from the one we use today?
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Henry MosleyDeveloped Modern Periodic Table

• 1911 Rearranged table according to increasing
  atomic number cleared up Mendeleevs mistakes
• Developed concept of atomic numbers after
  Rutherford discovered the proton
• Remember, atomic number protons
  neutrons

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Periodic Law

• When placed in increasing atomic number, elements
  have a predictable chemical and physical behavior
• It is the electron configuration that determines
  an elements behavior
• The periodic table is arranged so that elements
  with similar properties fall in the same column

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Periodic Table Terminology

• Group elements in a column of the periodic
  table
• There are 18 groups
• Groups are sometimes called families
• Period elements in the same row of the periodic
  table
• There are 7 periods

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Trends and the Periodic Table

• Group trend
• Trends or characteristics as you move down a
  group (family)
• Periodic trend
• Trends or characteristics as you move across a
  period

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For more information

• http//www.chemsoc.org/viselements/pages/history.h
  tml
• http//www.wou.edu/las/physci/ch412/perhist.htm
• http//web.buddyproject.org/web017/
  web017/history.html
• http//www.nidlink.com/jfromm/hist
  ory2/chemist5.htm