> For the complete documentation index, see [llms.txt](https://knowmayus.gitbook.io/chemistry/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowmayus.gitbook.io/chemistry/unit-1/development-of-periodic-table.md).

# Development Of Periodic Table

**J.W. Dobereiner ( 1780 - 1849 )** 

* Law of Triads ( 1817)

  * In groups of 3 --> Organized based on Atomic Weight & similar properties

**J.A.R.** **Newlands ( 1837-1898 )** 

* Law of Octaves ( 1865 ) 
  * When organized by atomic weight, he noticed that elements have similar properties in 7 intervals. ( Octaves of 7 elements )

**Lothar Meyer ( 1864 )** 

* Organized 28 elements into 6 different families with having similar Physical & Chemical Properties.
* Used the Valence Electrons to help organize and keep the families maintained in a set pattern ( Not specified how )

**Dmitri Mendeleev ( 1834 - 1907 ) :** 

* Periodic Law (1869 ) 
  * Elements were sorted by Atomic Weight
    * Similar Physical & chemical properties.
  * Able to predict existence & properties of other elements

**Henry Mosely ( 1887 - 1915 )**

* **Modern** Periodic Table ( 1913 ) 
  * Arranged in order of increasing atomic number ( Z ) 
    * Properties recurred periodically
*


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