The Periodic Table — Question 9

The contributions of Mendeleeff towards the periodic table are:

1. Elements were arranged in increasing order of atomic weights in horizontal rows called 'periods' and vertical columns called 'groups'.
2. Elements which are similar with respect to their chemical properties are grouped together and have atomic weights of nearly the same value.
3. Elements in the same group had the same 'valency' and similar chemical properties.
4. Based on the periodicity of properties a number of gaps were left in the table for undiscovered elements i.e., elements now discovered e.g., Scandium, Gallium and Germanium originally called eka-boron,eka-aluminium and eka-silicon respectively.
5. The properties of undiscovered elements left in the vacant gaps was predicted.
6. Incorrect atomic weights of some of the arranged elements were corrected with the knowledge of the atomic weights of the adjacent elements.