Note on Mendeleev's Periodic Table

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Mendeleev's periodic law: It states, "All the physical and chemical properties of the elements are the periodic function of their increasing atomic weight".

http://periodictabledevelopment.wikispaces.com/file/view/Dmitri_mendeleev.jpg/189958890/Dmitri_mendeleev.jpg

Fig: Dimitri Mendeleev

Atomic weight: It is the sum of number of protons and neutrons present in the nucleus of an atom.

http://i.imgur.com/5W4WkdY.jpg

Mendeleev's periodic table:

http://www.msnucleus.org/membership/html/jh/physical/periodictable/images/MendeleevPeriodic.gif

Merits of Mendeleev's periodic table:

  1. Mendeleev's periodic table was the first scientific and systematic classification system that made the study of all the known elements easier and more practicable.

    http://i.imgur.com/T7zyfV5.jpg

  2. Many elements were not discovered during the time of Mendeleev, so he knowingly left some gaps for the undiscovered one.

    http://i.imgur.com/EWGPOZv.jpg

  3. The atomic weight of some elements like Beryllium, platinum, gold, uranium, etc. appeared to be doubtful in the periodic table before Mendeleev periodic table came in prominence. Mendeleev's periodic table gave the right positions to such elements by studying the properties of them.

  4. Mendeleev's periodic table inspired subsequent chemists to discover new elements as he left some gaps for them.

Demerits of Mendeleev's periodic table

  1. Position of hydrogen: The position of hydrogen in his periodic table is not properly defined. Sometimes hydrogen loses electron like Group I elements and sometimes it gains electrons like those of group VII. Due to this property of hydrogen, it can be placed either in group I or group VII.
  2. Separation of chemically similar elements: Some chemically similar elements have been placed in different groups such as copper and mercury, gold and platinum, silver and thallium, barium and lead.
  3. Grouping of chemically dissimilar elements: Certain chemically dissimilar elements have been placed in the same group. For example: Copper, silver and gold have been placed in group I along with highly electropositive metals like lithium, sodium and potassium.
  4. Position of isotopes: Isotopes have the same atomic number, similar chemical properties but different atomic masses. Based on the periodic law, an isotope is an element, which must have a separate place in the periodic table. However, there are no places for isotopes in his periodic table.
  5. Anomalous pair of element: Certain elements having higher atomic weights have been placed wrongly before those with less atomic weight. For example, Argon (Ar) having higher atomic weight(39.9) has been placed before Potassium (K) with atomic weight (39).

    http://i.imgur.com/S3mYdGV.png

  6. Position of lanthanides and actinides: The fourteen elements from atomic number 58 (cerium) to 71 (lutetium) are termed as lanthanides (rare earth elements). These element have similar properties with that of lanthanum (Last). The elements from atomic number 90(thorium) to 103 (lawrencium) are termed as actinides (trans-uranium elements). These elements have similar properties with that of actinium. Mendeleev could not arrange their property in the fixed position.
  7. Position of iron and platinum group: Three elements such as Fe, Cu and Ni are placed in the group VIII. If these elements are separated, the periodic functions of the Mendeleev's periodic table will lost.
  8. Mendeleev's periodic table was not able to explain the atomic properties of the elements like valency, metallic characters, reactivity, ionization potential, etc.

  • Mendeleev's periodic law states that "All the physical and chemical properties of the elements are the periodic function of their increasing atomic weight".
  • Mendeleev's periodic table is the first scientific and systematic classification system that made the study of all the known elements easier and more practicable.
  • Many elements were not discovered during the time of Mendeleev, so he knowingly left some gaps for the undiscovered one.
  • Position of hydrogen, grouping of chemically dissimilar elements, position of isotopes, anomalous pair of element, position of lanthanides and actinides, position of iron and platinum group etc. are the demerits of Mendeleev's periodic table.
  • Mendeleev's periodic table was not able to explain the atomic properties of the elements like valency, metallic characters, reactivity, ionization potential, etc.
.

Very Short Questions

Mendeleev's periodic table

Modern periodic table

i. Elements are arranged in order of increasing atomic mass.

ii. There are nine vertical columns called groups.

iii. Transition elements are arbitrarily placed together in group VIII.

iv. There are some gaps for undiscovered elements.

v. There is not proper place for the inert gases.

i. Elements are arranged in order of increasing atomic number.

ii. There are eighteen vertical columns called groups.

iii. Transition elements are placed in the middle of long periods.

iv. There are no any gaps for the new elements.

v. The inert gases are arranged in zero group, extremely in left side of the periodic table.

The following are the characteristics of Mendeleev's periodic table:

  1. Elements are grouped on or more fundamental basis than earlier attempts.
  2. The discovery of new elements like inert gases did not disturb his periodic table.
  3. Some gaps were kept for new elements.
  4. Because of placement of new elements in the periodic table, properties of several elements like scandanium, gallium and germanium could be predicted.

Mendeleev left some gaps in his original periodic table for the undiscovered elements like titanium, gallium, scandium and germanium. When these elements were discovered later on, they were placed in those gaps, without disturbing the existing arrangement of elements.

The Mendeleev's periodic law states that, “The physical and chemical properties of elements are periodic function of their atomic weights.

The drawbacks of Mendeleev's periodic table are:

  1. The position of hydrogen were not clear in the Mendeleev's periodic table as the hydrogen shows the properties of both of group- IA and group VII A.
  2. There were no proper places of isotopes of the same elements as the elements were arranged on the basis of atomic weight.
  3. Mendeleev's periodic table did not have proper place for Lanthanides and Actinides.
  4. Certain elements which appear to be chemically similar like Cu and Hg, Au and Pt, etc. had been placed in separate groups.
  5. Certain elements which appear to be chemically dissimilar had been grouped together. For example, Cu, Ag and Au had been grouped together with Li, Na, K, etc.

The anomalies of Mendeleev's periodic table are:

  1. The position of hydrogen were not clear in the Mendeleev's periodic table as the hydrogen shows the properties of both of group- IA and group VII A.
  2. There were no proper places of isotopes of the same elements as the elements were arranged on the basis of atomic weight.
  3. Mendeleev's periodic table did not have proper place for Lanthanides and Actinides.
  4. Certain elements which appear to be chemically similar like Cu and Hg, Au and Pt, etc. had been placed in separate groups.
  5. Certain elements which appear to be chemically dissimilar had been grouped together. For example, Cu, Ag and Au had been grouped together with Li, Na, K, etc.

because it is resemble with both Group IA and VIIA of periodic table.

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  • The sum of number of protons and neutrons present in the nucleus of an atom is called ______.

    atomic number


    atomic weight


    none of above


    atomic mass


  • The law, 'all the physical and chemical properties of elemnts are periodic function of their atomic weight' is given by ______.

    modern law


    heisenberg


    none of above


    Mandeleev


  • The vertical rows in a periodic table are called ______.

    alkali metals


    nobel gases


    rows


    period


  • The physical and the chemical properties of elements are the periodic functions of their atomic weights is ________________________.

    Dalton's periodic table
    Mendeleev's periodic table
    Lothar's periodic table
    Modern periodic table
  • which element symbol is derived from german language?? 1)Titanium 2)Tantalum 3)Tungsten 4)Tin

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Melancholia2

This isn't a question, but you really should put the date when you created this website so its easier to reference lol


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