Johann Dobereiner

1. The Periodic TableCourtesy of Periodic Table of the Elements v. 4.0by Kostas Tsigaridis (http://ptoe.move.to/)

2. Johann Dobereiner • In 1829, elements into groups of 3 • triads. • similar chemical properties and physical properties. (ex. Cl, Br, I and Ca, Sr, Ba) Model of triads 1780 - 1849

3. John Newlands -In 1863, arranged in “octaves” -(after arranging in order of increasing atomic mass) =certain properties repeated every 8th element. Why? !!!!! Law of Octaves 1838 - 1898

4. REVIEW 1. Dobereiner arranged elements into groups called THE MODEL of _________? 2. Why were there only 3 elements in each group? 3. The Law of Octaves developed by _______ _________, worked well at the time because of which rule we know today?

5. Dmitri Mendeleev is called the Father of the Periodic Table • 1834-1907 • Chemistry Professor at St. Petersburg University • He wrote a textbookPrinciples of Chemistryand organized elements by similar properties

6. In 1869 ,Based upon patterns he noticed when relating atomic mass, physical & chemical properties, he developed a Periodic Table of 63 elements • VERY GOOD HOT PIES (Vertical Groups / Horizontal Periods) • He predicted 3 unknown elements and their properties (germamium, scandium, and gallium).

7. Lothar Meyer • At the same time, 1869, Meyer published his own table of the elements organized by increasing atomic mass. • 1830 - 1895

8. Review: • 1. Dmitri Mendeleev put his periodic table in order of increasing_____ _____? • 2. Mendeleev noticed that when the elements were in order of increasing _____ ____ , their chemical/physical properties __________. • 3.What does VERY GOOD HOT PIES stand for? • How did Meyer arrange his Periodic Table?

9. Both Mendeleev and Meyer arranged the elements in order of increasing atomic mass. • Both left vacant spaces where unknown elements should fit. • So why is Mendeleev called the “father of the modern periodic table” and not Meyer, or both?

10. Mendeleev… • stated that if the atomic weight of an element caused it to be placed in the wrong group, then the weight must be wrong. (He corrected the atomic masses of Be, In, and U) • was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown.

11. After the discovery of these unknown elements between 1874 and 1885, and the fact that Mendeleev’s predictions for Sc, Ga, and Ge were amazingly close to the actual values, his table was generally accepted!

12. Henry Moseley • Henry Moseley (1887-1915) In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements*. In 1913, he rearranged the elements in order of increasing atomic number.

13. Interest FACT….. • Moseley’s research was halted when the British government sent him to serve as a foot soldier in WWI. He was killed in the fighting in Gallipoli by a sniper’s bullet, at the age of 28. Because of this loss, the British government later restricted its scientists to noncombatant duties during WWII.

14. REVIEW: • 1. Henry Moseley put his periodic table in order of increasing ______ _______? • 2.What can you infer about elements in the same group? • Who is considered the FATHER of the PERIODIC TABLE?

15. Glenn Seaborg, 1912- 1999, was a Chemistry professor at the University of California at Berkeley • He was the first to propose rearranging the Table by adding the Actinide Series • He discovered and isolated 10 transuranic elements (plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium and seaborgium)

16. REVIEW: • 1. ___________ was the first to propose rearranging the Table by adding the ___________ ________. • 2.What is the atomic number of the element named after Seaborg? (the only person to have an element named after them while living.)