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  1. 1. Periodic Trends: Searching for Pattern• In the 1800’s, chemists were decomposing compounds and discovering elements• By 1860, about 70 of the 113 elements were discovered• How should these be organized in an order that made sense? Dmitri Mendeleev
  2. 2. The Early Periodic Table Sodium• Mendeleev, Mid-1800’s• Wrote element names and Potassium properties on cards• Experimented with different arrangements
  3. 3. What Did He Discover?• He noticed that elements eight to the right and eight to the left had similar properties Mendeleev’s Table
  4. 4. Modern Periodic Table MetalNon-Metal Metalloid Transition MetalNoble Gases
  5. 5. Atomic Size• As you move across the table atoms get smaller (Proton Pull)• As you move down the table, atoms get larger (Shielding Effect)
  6. 6. Ionization Energy: the energy required to remove an electron from an atom• I.E. increases as you go across the table• I.E. decreases as you go down the table