| 1 | Elements are arranged in the increasing order of their atomic masses. | 1 | Elements are arranged in the increasing order of their atomic numbers. |
| 2 | There are a total of 7 groups (columns) and 6 periods (rows). | 2 | There are a total of 18 groups (columns) and 7 periods (rows). |
| 3 | Elements having similar properties were placed directly under one another. | 3 | Elements having the same valence shell are present in the same period while elements having the same number of valence electrons are present in the same group. |
| 4 | The position of hydrogen could not be explained. | 4 | Hydrogen is placed above alkali metals. |
| 5 | No distinguishing positions for metals and non-metals. | 5 | Metals are present at the left hand side of the periodic table whereas non-metals are present at the right hand side. |
