1. Sort it out! American Girl Time Wired Ladies Home Journal Cosmopolitan Humpty Dumpty Newsweek Scientific American Lutheran Magazine Sports Ilustrated Dog Fancy Beading People Consumer Reports on Health Military History Dragon Mad Rolling Stone Auto Travel Truckin’ Fortune Consumer’s Digest Reader’s Digest Cat’s Fancy Ranger Rick Highlights Popular Mechanics TV Guide BonAppetit Watercolor Taste of Home National Geographic Redbook National Lampoon Ebony Guitar Player National Review Pc Magazine Teen Vogue New Republic Catholic Digest Cruise Trade Field and Stream Esquire MacWorld Tiger Beat Travel Weekly Xbox Videogamer GQ Car and Driver Snowboarder ESPN Smithsonian

2. Figuring it out By the mid-1800’s there were 62 known elements, but no system to understand them!

3. How did we get this?

4. Periodic Table How did they figure it out? They observed physical and chemical properties and looked for repeating patterns. PERIODIC: happening or appearing at regular intervals regularly repeating pattern

5. What does PERIODIC have to do with SCIENCE? Scientists use patterns to help us figure things out. After all…s’tI namuh erutan ot erugif sgniht tuo… The patterns help explain chemical behavior and details about atomic structure. Patterns help us predict.

6. Dobereiner German chemist in the early 1800’s Developed concept of TRIADS – Groups of 3 elements with similar properties in which the middle element has average of the other 2 Cl36 amu1.6 g/L Br80 amu3.1 g/L I127 amu5 g/L Ca40 amu1.6 g/mL Sr86 amu2.6 g/mL Ba137 amu3.5 g/mL

7. Newlands English chemist 1865 Law of Octaves – The properties of elements repeated every 8 elements…like an octave in music Everyone laughed! But he was eventually credited with the idea of a periodic pattern to the properties of the elements

8. MENDELEEV Russian chemist 1869 Wrote elements their properties on cards and arranged them different ways according to the different properties Noticed periodic repetition of properties when cards were arranged by atomic mass

9. He had a problem! Some elements did not fit the pattern If he sorted by properties, some were out of order according to masses! Check Periodic table for examples: – Ar/K Co/Ni Te/I Why? He lived in the 1800’s and didn’t know about the parts of an atom. All he knew was atomic mass. Protons and neutrons and the idea of isotopes would have helped him.

10. What did he do? He boldly broke the pattern of atomic mass to keep the properties together. He even proposed that the masses were wrong! He predicted the discovery of elements to fill gaps, and he correctly predicted their properties.

11. He predicted missing elements. Here’s one. PropertyEkasiliconGermanium Atomic mass72 amu72.59 amu Density5.5 g/cc5.35 g/cc Melting pointhigh947 degrees C Colorgray Predicted 1869Discovered 1882

12. Father of the Periodic Table

13. Moseley English chemist early 1900’s Solved the problem of elements out of order according to mass Developed the concept of ATOMIC NUMBER, the number of protons in the nucleus. The correct way to order the chart is by ATOMIC NUMBER not atomic mass. Mendeleev’s exceptions fell into place when ordered by number, not mass. Isotopes (unknown at the time) threw off the order by mass.

14. ALL of these scientists contributed to the PERIODIC LAW When elements are arranged in order of INCREASING ATOMIC NUMBER, their physical and chemical properties show a PERIODIC PATTERN. (The properties repeat regularly.) From this To ths

15. PERIODIC TRENDS We can predict many things. The periodic table is organized so that the elements with similar electron configurations are in the same column or family. Many properties of elements change in a predictable way as you move through the periodic table. These variations are called PERIODIC TRENDS.