1. The Periodic Table Dmitri Mendeleev - put elements in a periodic chart based on mass - left spaces for elements to be discovered Henry Moseley placed elements based on number of protons

2. Design of the Periodic Table Columns or Families up and down numbered 1 through 18 elements in column have similar properties elements have same number of valence electrons Periods across the table (horizontal) numbered 1 – 7 electrons share the same energy level

3. Valence Electrons the number of electrons in the outermost energy level

4. Metals left of the zigzag on table Properties of metals: shiny luster high densities good conductors of heat & electricity high melting points

5. Metals most are ductile and malleable metals lose electrons react easily with O 2 and atmosphere

6. Metals Video

7. Nonmetals right of the zigzag on table Properties of nonmetals: dull luster low densities poor conductors of heat & electricity low melting points

8. Nonmetals most are brittle and break easily nonmetals gain electrons 5, 6, 7, or 8 valence electrons are present

9. Nonmetals Video

10. Metalloids located on either side of the zigzag line (except aluminum which is a metal) these elements have characteristics of both metals & nonmetals

11. Metalloids Video