What is the merit and demerit of mandeleevs periodic table?

Answer 1

Merits of Periodic Table

1. The classification of elements is based on the atomic number, which is a more fundamental property.

2. The reason for placing isotopes at one place is justified as the classification is on the basis of atomic number.

3. It explains the periodicity of the properties of the elements and relates them to their electronic configurations.

5. The position of the elements that were misfits on the basis of mass number (anomalous pairs like argon and potassium) could be justified on the basis of atomic number.

6. The lanthanides and actinides are placed separately at the bottom of the

periodic table.

7. The table is simple, systematic and easy way for remembering the properties of various elements as it is based on the electronic configuration.

Demerits are

1. Position of Hydrogen is still in dispute to keep weather in Alkali, Crystallogens ,or Halogen

2. Lanthanides and Actinides are kept away from main body

3. Helium is of s-block still kept in p-block due to noble gas property

Answer 2

merits-

1. systematic arrangements of 66 elements in groups and periods.

2. corrected doubtful masses of some elements like Be,Pd,Pt etc.

3. predicted properties of elements which were not discovered -like scandium , gallium , germanium , which were correct and left gaps for them.

demerits-

1. controversial position of hydrogen.

2. position of isotopes were not correct.

3. two similar elements like Cu & Hg were grouped differently.

4. Co with higher atomic no. was placed before lower atomic no. Ni which was contradicting arrangement of element in increasing atomic no.

5. did not provide space for noble gases which were discovered later.

6. no space left for isotopes.

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Answer 3

advantages:---

1:---mendeleev periodic law predicted the existance of some elementd that had not been discovered at that time

i.e.:-gallium,scandium, germanium

2:-----his periodic table could accommodate noble gases when they were discovered

disadvantages:-----

1:-----he did not explained the position of isotopes,

like:-2 isotopes of chlorine are cl-35, cl-37

these having two atomic masses in the same group

2:-----wrong order of atomic masses of some elements could not explained

see in group no. 8

3:-----a correct position could not be assigned to hydrogen in the periodic table]

Answer 4

Merits

• Mendeleev's table helped in the correction of doubtful atomic masses of certain elements with the help of their expected positions and properties, for example, beryllium (Be).

• It predicted the existence of some new elements that were not discovered at the time the table was created.

Demerits

• The atomic weights of two pairs of elements were reversed. Cobalt (Co) and nickel (Ni); vanadium (V) and chromium (Cr) are the two anomalous pairs as the Atomic Mass of cobalt which is placed before nickel is more and similarly atomic mass of vanadium placed before chromium is more.

• Atomic masses do not increase in a regular manner in going from one element to the next. So it was not possible to predict how many elements could be discovered between two elements.

• Lanthanoides and actinoides were not given proper place in the periodic table.

• Isotopes were not placed in the periodic table.

Like alkali metals, hydrogen combines with halogens, oxygen and sulphur to form compounds with similar formulae. Like halogens, hydrogen exists as diatomic molecule and combines with metals and non-metals to form covalent compounds. So he could not assign a correct position to hydrogen.