History of Periodic Elements

• Henry Mosely used x-ray to see the atomic number of elements. therefore, he arranged them according to atomic number.
• Who created groups and periods of the periodic table and revised Mendeleev's framework?

  Henry Mosely. He's also responsible for the modern periodic table.
• Dmitri Mendeleev made the framework for the modern periodic table along with Lothar Meyer. Arranged the elements by atomic mass. (1869)
• Who arranged the elements in 8 groups and what was the arrangement called? 

  John Newlands

  The law of octaves - when elements were arranged by atomic mass he was able to observe that every eighth element had similar properties

  However, it failed because only elements with low atomic mass adhered to the law. More so, it did not account for the existence of noble gasses
• John Newlands arranged the elements by atomic mass  and arranged the elements in 8 groups (1864)
• Who grouped elements according to triads? And what were those triads

  
  

  Johann Wolfgang Dobereiner

  Dobereiner's triads - the middle element's weight is the approximated average value of the two other elements

  However, it failed due to its inaccuracy as the law was inapplicable to other elements. He did not leave gaps as well and some other elements were still unknown during his time
• Johann Wolfgang Dobereiner grouped elements based on similarities in properties and increased the elements according to their atomic mass (1829)
• Antoine Lavoisier was the scientist who grouped the elements into metals and nonmetals (1789)