1. The Periodic Table From 56 to 118 in only 150 years!

2. The Ancient Greeks The scientists and philosophers of ancient Greece believed there were 4 elements:  Earth  Wind  Fire  Water

3. And with other things to think about, pretty much nobody cared to dispute the fact for hundreds (maybe thousands!!) of years

4. Until the mid 19 th century… When several scientists, working independently, tried to come up with a logical arrangement of the known elements at the time.

5. Dimitri Mendeleev (Dee-me-tree Men-da-lay-ev) In 1863, a Russian scientist and teacher named Dimitri Mendeleev decided to order the 56 known elements. He considered their periodicity (repeating pattern of properties). He decided to arrange them by increasing atomic weight.

6. Mendeleev’s first table looked like

7. By 1871, more elements were known,

8. Amazingly, Mendeleev was able to  Order elements by relative size and show periodicity  Show that columns of elements (families) had similar chemical behaviors  Predict elements yet to be discovered

9. Now Scientists use periodic tables that look like…

10. And sounds like this…

12. Or maybe even this…

13. Nice work Dimitri!

15. The End Or is it?