The major differences between Mendeleev's and Modern periodic table are as follows:
| Mendeleev's periodic table | Modern periodic table |
| Elements are arranged in the increasing order of their atomic masses. | Elements are arranged in the increasing order of their atomic numbers. |
| There are total number of 8 groups and 6 periods. | There are a total number of 18 groups and 7 periods. |
| Elements having similar properties were placed directly under one another. | Elements having same valance shell are present in the same period while elements having the same number of valence electrons are present in the same group. |
| The position of hydrogen could not be explained clearly. | Hydrogen is placed above alkali metals. |
| There was no distinguishing positions for metal and non metals. | Metals are present at the left hand side of the modern periodic table whereas non metals are present at the right hand side. |
