1. Elements
•By mid 1800’s many elements were discovered

2. Mendeleev Arranged elements by atomic mass
Elements with similar properties were side by side
Many blanks in table where no known elements fit
Correctly predicted properties of unknown elements prior to their discovery

4. Problems with mass Te and I would switch places Co and Ni same mass
Ar and K would switch places

5. Moseley • 1913 discovered atomic number
• Rearranged table by atomic number
• Currently used today

6. Periodic Table Rows are called periods
Properties change as go across periods
Move from one period to next, properties repeat

8. Periodic Law
When elements are arranged in order by atomic number there is a periodic repeat of chemical and physical properties: elements with similar chemical and physical properties end up in the same column.

9. Periodic Table Columns are called groups or families
Each group is identified by a number and either an A or B

10. Group A Elements 1A to 7A & 0 are representative elements
Three groups of representative elements

11. Metals
High luster
High electrical conductivity
Malleable
Ductile

12. Nonmetals
Nonlusterous
Poor conductors of electricity

13. MetalIoids
Properties in between metals and nonmetals.
Semi-conductors

14. Families/Groups IA - Except H- Alkali metals
2A - Alkaline Earth metals
7A - Halogens
0 - Noble gases / Inert gases
3B - 2B- Transition metals
Lanthanide /Actinide-series - Inner Transition elements