CBSE Class 10 Answered
Differences between Mendeleev's Periodic table and Modern periodic table:
Mendeleev's periodic table |
Modern Periodic table |
1. According to Mendeleev theory, The physical and chemical properties of elements are a periodic function of their atomic masses. |
1. Modern periodic law states that, the properties of elements are a periodic function of their atomic numbers. |
2. The basis of classification was the formula of hydrides and oxides made by the elements. |
2. The basis of classification is the electronic configuration of the elements. |
4. The noble elements were not included in the table, as they were not discovered at that time. |
4. Modern periodic table included noble elements in group 18 as a last and separated group. |
5. It has an ambiguity in position of some elements as, some elements with larger atomic weights are placed before elements with smaller atomic weight without any justified reason. |
5. Here, all are arranged systematically with increasing atomic number and weight too. |
6. According to this theory, the isotopes with different atomic weights, should be placed in different positions, but are not given any position and no, justified reason was explained. |
6. The isotopes were assigned same position as they have same atomic number. |
7. Some different elements were grouped together while some similar elements were placed in different groups. Ex: alkali metals like Li , Na, K were placed with coinage metals Cu, Ag, Au etc. |
7. No such confusion, the coinage metals have their own position in d-block and alkali metals are placed in s-block elements. |
8. Group VIII has three elements together, as Fe, Co, Ni |
8. These elements are placed in different groups, under d-block elements. |
Besides these differences, there are various chemical and physical differences in properties of elements in the two periodic tables.