Mention 4 defects in Mendeleev's periodic table.
Answers
1). The chemical properties of hydrogen is similar with the elements of 7th group although it was kept in 1st group.Hence, the position of hydrogen is not fixed.In fact, the position of hydrogen is not fixed in Mendeleev's periodic table.
2). The isotope elements are not included in Mendeleev's periodic table.
3). Metal,non-metal and metalloids are not seperated.
4). The lanthanides and actinides are not included in the main body of periodic table.
Answer:
Explanation:Anomalous Pairs
The following pairs of elements don’t follow the follow Mendeleev’s Principles:
Cobalt (58.9) with a higher atomic mass precedes Nickel (58.6) in the periodic table.
Tellurium (127.6) with a higher atomic mass than Iodine (126.9) precedes it in the periodic table.
Grouping of chemically dissimilar elements
Elements such as Copper and Silver bear no resemblance with the alkali metals, but they have been placed together in the first group.
Position of Isotopes
According to Mendeleev’s Periodic Law, isotopes of an element must be given separate places in the periodic table because they have different atomic masses.
Electronic arrangement
It does not explain the electronic arrangement of elements.
Separation of chemically similar elements
Elements that are chemically similar such as Gold and Platinum have been placed in separate groups.
The position of hydrogen
Hydrogen was not given a fixed position because it was considered in Group IA as well as in Group VIIA.