Question

How could the Modern Periodic Table remove various anomalies of
Mendeleev's Periodic Table?​

Answer 1

Answer:

1. In the Modern Periodic table elements are arranged in the increasing order of their atomic number. This removes the anomaly regarding certain pairs of elements in Mendeleev’s periodic table.

2. Atomic number of cobalt is 27 and nickel is 28. Hence cobalt will come before nickel even though its atomic mass is greater.

3. All isotopes of the same elements have different atomic masses, but same atomic number; therefore they are placed in the same position in the modern periodic table.

4. In Modern periodic table elements are classified according to their electronic configuration into different blocks. Thus, various anomalies (irregularity) which were seen in Mendeleev’s table due to the arrangement according to atomic masses were overcome by the Modern Periodic table.  

5.  Hydrogen was placed in group 1 and in group 17 as it resembles alkali metals as well as halogens. Therefore, no fixed position could be given to hydrogen in Mendeleev’s periodic table.  But in Modern periodic table it is placed in group 1.

Answer 2

Answer:

Modern Periodic Table or Long Form of Periodic Table: In the Modern Periodic Table, the elements are arranged in increasing order of their atomic numbers.

The Modern Periodic Table was formulated by Henry Moseley in 1913.

Modern Periodic Law: It states that “the properties of elements are a periodic function of their atomic numbers.”

Main Features of Modern Periodic Table

The elements are arranged according to their electronic configurations.

There are seven periods, numbering 1 to 7. The period number signifies the number of electron shells of an element. Thus, the period one elements have only one shell. The period two elements have only two shells, and so on. Period 1 is the shortest period with only two elements. Periods 2 and 3 are short periods with eight elements each. Periods 4 and 5 are long periods.