Disadvantage of mendeleev potable

Disadvantages:

1. Anomalous pairs: Argon with atomic mass 39.9 precedes potassium with atomic mass 39.1.

Cobalt with atomic mass 58.9 precedes nickel with atomic mass 58.6.

Tellurium with atomic mass 127.6 precedes iodine with atomic mass 126.9.

2. Position of isotopes: According to Mendeleev's periodic law, isotopes of an element must be given separate places in the periodic table since they have different atomic masses. But they were not assigned separate places.

3.Grouping of chemically dissimilar elements: Elements such as copper and silver bear no resemblance to alkali metals but they have placed in separate groups.

4.Separation of chemically similar elements: Elements that are chemically similar, such as gold and platinum have been placed in separate groups.

5.Electron arrangement: It does not explain the electron arrangement of elements.

6. Position of Hydrogen: It was not given in a fixed position.

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".