Mendeleevs Periodic Table and Law

Mendeleev’s Periodic Table and Law

  • According to Mendeleev periodic table the properties of elements are periodic function of their atomic masses.
  • Only 63 elements are known at that time.

Achievements of Mendeleev’s Periodic Table

  • Mendeleev left proper gaps for some elements that had not been discovered at that time. 
  • He names these as Eka to the name of the preceding element.
  • For Example Eka aluminum, Eka Boron, Eka silicon  have a similar properties with Gallium, scandium, and Germanium which were discovered later . 
  • Noble gases were discovered late because they are inert and have a low concentrations in the atmosphere. Mendeleev put noble gases in separate groups that did not disturb the original Mendeleev table.

Limitations of Mendeleev’s Periodic Table

  • Hydrogen resembles both, the alkali metals (IA) and the halogens (VIIA) in properties, so, Mendeleev could not justify its position.
  • Atomic weight of isotopes differ, but, they were not placed in different positions in Mendeleev’s periodic table.
  • Cobalt (Co) has higher atomic weights but was placed before Nickel (Ni) in the periodic table.
  • Platinum (Pt) and Gold (Au) have similar properties but were placed in different groups.
  • He could not explain the cause of periodicity among the elements.