Question

Hola Brainlians!!!

Explain the defects of Modern periodic table .

Class - 10th
Chapter - Periodic classification of elements.

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Answer 1

★ Solution :-

The defects of modern periodic table are ::

• Position of Hydrogen ::

Position of Hydrogen, is still controversial in the modern periodic table . If we look at the structure of Hydrogen, then it has one electron in its outermost shell similar like alkali metals. But if we see bonding and other features of hydrogen, then it behaves like Group 17 elements similar like Halogens. So for now Hydrogen is placed on the top of periodic table not specifically in any group or period. Instead it is kept seperately.

• Positioning of unordered pair :: According to a general trend in modern periodic table, ionisation enthalpy increases as we go from right to left in a period. But at some places the ionisation enthalpy of preceding elements fpr example, Beryllium has higher ionisation enthalpy than Boron.

• Hydration Enthalpy :: It is a general trend in modern periodic table, that hydration and enthalpy increases as we go down the group. But for alkaline metals, Lithium being the first element in Group 1, has highest hydration enthalpy than other elements in that group.

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★ More to know :-

• Modern Periodic Law : Atomic Numbers are the function of physical and chemical properties of elements.

• Mendeleev Periodic Law : Atomic Mass is the function of physical and chemical properties of elements.

• Dobreniers Triad : In this classification the average of sum of atomic mass of first and third element is equal to the atomic mass of second element.

Answer 2

$\Large\mathsf{Answer}$

The important advantages of the modern periodic table are given below :

• This classification is based on the atomic number which is a more fundamental property of the elements.

• Since this classification is based on the atomic number and not on the atomic mass, the position of placing isotopes at one place is fully justified.

• It is easy to remember and reproduce.

• The systematic grouping of elements into four blocks; s, p, d and f has made the study of the elements more simple.

• The position of some elements which were misfit on the basis of atomic mass is now justified on the basis of atomic number. For example, argon precedes potassium because argon has atomic number 18 and potassium has 19.

• The lanthanoids and actinoids which have properties different from other groups are placed separately at the bottom of the periodic table.

The main defects of this table are :

• The position of hydrogen is not settled. It resembles with alkali metals as well as halogens. However, it has been placed with alkali metals.

• Lanthanoids and actinoids have not been accommodated in the main body of the periodic table.

❥︎Hope it helps

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