1. The History of the Modern Periodic Table

2. 19th century: Chemists began to categorize the elements Used:
Similarities in their properties, both physical and chemical.
Result -> our modern periodic table.

3. Johann Dobereiner Model of triads 1780 - 1849
1829: Classified some elements into groups of 3 - called triads
Model of triads
(example: Cl, Br, I and Ca, Sr, Ba)

4. John Newlands Law of Octaves 1838 - 1898
1863: Arranged elements in order of increasing atomic mass
Suggested elements can be arranged in “octaves” because he noticed that certain properties repeated every 8th element.
Law of Octaves

5. 1838 - 1898 Law of Octaves Newlands' claim was met with great ridicule
Was told his classification was as arbitrary as putting them in alphabetical order.
His paper was rejected for publication by the Chemical Society.
Law of Octaves

6. Demitri Mendeleev
1869-> Published a table of the elements organized by atomic mass.
increasing

7. Lothar Meyer 1830 - 1895 At the same time, published his own table
of the elements organized by increasing atomic mass.
WHAT??? 2 papers, same thing

8. Elements known at this time

9. 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 mass of an element caused it to be placed in the wrong group, then the mass must be wrong.
He corrected the atomic masses of Be, In, and U
So confident, used it to predict the physical properties of three elements that were yet unknown. Wow!

11. 1874 and * After the discovery of these unknown elements (and the fact that Mendeleev’s predictions were amazingly close to the actual values) his table was generally accepted.

12. Problems arose when new elements were discovered and more accurate atomic weights determined. L k at our modern periodic table, can you identify what elements might have caused chemists a headache?
Ar and K
Co and Ni
Te and I

13. Henry Moseley
1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements.
Rearranged the elements in order of increasing atomic number.

14. Glenn T. Seaborg 1912 - 1999 Co-discovered 10 new elements
1944 he moved 14 elements out of the main body of the periodic table.
Current location below the Lanthanide series.
 These became known as the Actinide series.

15. Only person to have an element named after him while still alive.
"This is the greatest honor ever bestowed upon me - even better, I think, than winning the Nobel Prize."

16. Periodic Table Geography

17. The horizontal rows of the periodic table are called PERIODS.

18. The elements in any group of the periodic table have similar physical and chemical properties!
The vertical columns of the periodic table are called GROUPS or FAMILIES.

19. Periodic Law
When elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties.

20. Alkali Metals

21. Alkaline Earth Metals

22. Transition Metals

23. InnerTransition Metals
These elements are also called the rare-earth elements.
InnerTransition Metals

24. Halogens

25. Noble Gases

26. And it will become your BFF this year. 
The periodic table is the most important tool in the chemist’s toolbox!
And it will become your BFF this year. 