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# Periodic Table C P

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### Transcript

• 1.
• 2. The History
• Dobereiner
• Found elements could be put in Triads
• Grouped By Similar Chemical Properties
• Many Properties of Middle Elements Are Approximate Averages Of The Properties Of The 1 st And 3 rd Element
• ELEMT ATOMIC MASS Density
• Cl 39.5 1.56
• Br 79.9 3.12
• L 126.9 4.95
• 4. J.A.R. Newlands (1837-1898)
• Presented the idea that when the elements were arranged in order of increasing atomic mass, the properties of every eighth element was like that of the first in the set:1 st -8 th , 2 nd -9 th , and so on
• Called the pattern the law of octaves
• 5. Dmitri Mendeleev (1834-1907) Lothar Myer (1830-1895)
• Published nearly identical schemes for classifying the elements
• Mendeleev is given more credit since he published first and was more successful at demonstrating it
• Mendeleev also put breaks in the Table where other elements were yet to be found b/c he knew they had to fit in to make the table work right
• 6. Mendeleev
• Wanted to make the elements easier to learn and understand
• Placed elements using their properties
• When arranged the elements by increasing atomic mass, could see a periodic repetition of their properties
• Used this to create the first Periodic Table
• 7. The History (Cont.)
• Moseley
• Developed atomic number concept for the atom
• Arranged elements by increasing atomic number rather than mass as Mendeleev had
• 8. The Periodic Law
• States that: When elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern.