what is the difference between Mendeleev periodic table and modern periodic table

Asked by hemalatha | 7th Jan, 2014, 07:22: PM

Expert Answer:

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.

Answered by Hanisha Vyas | 8th Jan, 2014, 11:34: AM

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