1. October 28 th, 2015 Go over assessment. Start Unit 4 on The Periodic Table Bell Ringer Go the my teacher page and under Unit 4 read pages 1 & 2“About the Periodic Table”

3. Johann Dobereiner German chemist 1817 Triads – groups of three elements grouped by their similar properties. John Newlands English chemist 1864 Found that similar properties (he emphasized atomic weight and physical & chemical properties) repeated every eight elements – he called them octaves. William Odling English chemist 1857 Divided the known elements into 13 groups based on solubility.

4. Russian chemist 1869 Placed elements in order by their atomic masses. Left blank spots in his table for 3 undiscovered elements. Successfully predicted the properties of these undiscovered elements.

5. Mendeleev’s first draft of the Periodic System of Elements But…there was a problem…a few elements seemed to be switched around…Mendeleev concluded their atomic masses had been poorly calculated and switched them based on their properties.

6. British scientist 1913 Through his experiments with x- rays, discovered atomic numbers. Arranged the Periodic Table by these atomic numbers. This fixed Mendeleev’s problems. Periodic Law = the properties of the elements are a periodic function of their atomic numbers.

7. Mendeleev’s challenge was HUGE! Arrange many different properties in an arrangement that made sense for ALL the properties. PLUS, there were holes in his periodic table but he did not know where those holes were. Challenging? Your mission (and you will choose to accept it) is to…