1. The Chemist’s Calendar Presented by Sunni Bauers www.chemicalelements.com

2. Development of the Periodic Table In the 1880’s a Russian scientist, Dmitri Mendeleev, saw a hidden pattern in the elements. Mendeleev noticed that patterns appeared when the elements were arranged in order of increasing atomic mass. He realized that groups of elements had similar chemical and physical properties. He arranged the the elements according to increasing atomic mass and grouped the elements according to their properties. Today’s Periodic Table is now arranged according to increasing atomic number, otherwise it’s the same as Mendeleev’s.

3. Reading the Periodic Table The periodic table contains over 100 squares, one separate square for each element. Each square includes the element’s atomic number, chemical symbol, name, and atomic mass.

4. Inside the Squares Reading the Squares: The square for Lithium Lithium - Element’s Name 3 - Element’s Atomic Number (# of protons and electrons) Li - Element’s Symbol (one or two letters) 6.941 - Element’s Atomic Mass (# of protons and neutrons)

5. Organizing the Periodic Table The main body of the periodic table is arranged into eighteen vertical columns and seven horizontal rows. The elements in a column are called a group or a family. The elements in each group have similar characteristics. Each horizontal row across the table is called a period. The elements in each period are not alike in properties. As you move across a period, the elements change properties gradually and predictably.

6. Characteristics of the Types of Elements Metals - hardness, shininess, malleability, and ductility Nonmetals - dull, brittle, and poor conductors of heat and electricity Metalloids - some of the characteristics of metals and some of the characteristics of nonmetals

7. Sections of The Periodic Table Representative Elements - Groups 1 & 2 and the elements in Groups 13 - 18. Transition Elements - Groups 3 - 12

8. Representative Elements The Alkali Metals - Group 1 - most reactive elements Alkaline Earth Metals - Group 2 - less reactive than Group 1 Groups 13 - 18 - Contains metals, nonmetals, and metalloids

9. Transition Elements All Metals Groups 2 - 12 Uses of the some of the transition elements: iron, cobalt, and nickel - magnetic properties silver - photography copper - plumbing pipes silver and gold - jewelry chromium - used to make brightly colored paints californium - used to kill cancer cells americium - used in home smoke detectors

10. Comprehension Questions 1. How did Mendeleev organize the elements in his periodic table? 2. What are the two sections of the Periodic Table? 3. What does each square of the elements on the Periodic Table include? 4. What is one characteristic of metals? …of nonmetals? …of metalloids? 5. The Representative Elements consists of which groups? 6. The Transition Elements consists of which groups?

11. Works Cited www.chemicalelements.com www.chemistry.co.nz/mendeleev.