Note on Classification of Elements

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Applications of Periodic table

  1. Classification of elements: The main utility of the system is that it affords a scheme of classification of elements, which is helpful in the study of 109 elements is reduced to nine groups only.
  2. Prediction of new elements: Mendeleev left many gaps in his original table and their atomic mass, physical and chemical properties of the elements to be discovered: Later on these new elements to be discovered.
  3. Correction of doubtful atomic masses: Many doubtful atomic masses were corrected with the help of this classification.

Mendeleev's periodic table

Mendeleev's periodic table was based on atomic mass. In 1913, Mosley from his studies on x- rays found that the atomic number is the more fundamental property of an element than its atomic mass. Thus, atomic number was adopted as the basis of the modern periodic table.

Modern periodic table

The properties of elements are a periodic function of their atomic numbers. This means that if the elements are arranged in order of their atomic number, then elements with similar properties are repeated after a regular interval.

Modern periodic law:

The properties of elements are a periodic function of their atomic numbers. This means that if the elements are arranged in order of their increasing atomic number, then elements with similar properties are repeated after a regular interval. The periodic table based on this law is known as the modern periodic table.

Description of the long form of periodic table:

  1. In this periodic table, the elements are arranged in order of their increasing atomic number.
  2. There are seven periods. The first period contains two elements and is the shortest period. The second and the third periods containing 8 elements each are called short periods. The fourth and the succeeding periods are the long periods.
  3. The table has 18 vertical columns, but the number of the group is 16 only. This is because group VIII has three vertical columns.

Advantages of modern periodic table:

  1. The modern periodic table is based on the most fundamental property, the atomic number of elements, while Mendeleev's periodic table is based on the atomic masses of elements.
  2. In Mendeleev's periodic table, there are several anomalies, e.g. the position isotopes, wrong order of atomic masses of atomic masses of some elements, etc. In this long form of the periodic table, these anomalies have been removed.
  3. In this modern periodic table, the sub-groups A and B are clearly separate because the elements belonging to subgroup B have slightly different properties. In Mendeleev's periodic table, the sub-groups are kept together.

  • Classification of elements: The main utility of the system is that it affords a scheme of classification of elements, which is helpful in the study of 109 elements is reduced to nine groups only.
  • Mandeleev's periodic table was based on atomic mass. In 1913, Mosley from his studies on x- rays found that the atomic number is the more fundamental property of an element than its atomic mass. Thus, atomic number was adopted as the basis of modern periodic table.
  • Modern periodic law: The properties of elements are a periodic function of their atomic numbers.
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Very Short Questions

They are:

  • The position of hydrogen isn’t explained clearly or properties of hydrogen resemble with both group I and VIII elements.
  • Chemically dissimilar elements are kept in the same group. E.g, copper, argon, all are kept together with Li, Na, K.
  • While arranging on the basis of increasing atomic mass potassium are kept earlier than argon. But argon is kept earlier than potassium in his periodic table.
  • Metals and non-metals aren’t placed separately.

The modern periodic law states that the physical and comical properties of elements are the periodic functions of their atomic numbers.

The features of modern periodic table are:

  • There are seven horizontal rows which are known as periods. There are seven periods, period one is very short, 2 and 3are short, 4 and 5 are long , 6 is very long and 8 is long but incomplete period.
  • There are IX groups in the modern periodic table. Among 9 group I to VIII are sub-divided into sub-groups A and B. Group VIII has three vertical columns and there is one group.
  • In group, I almost reactive metal in group VII a most reactive non-metals in 0 group inert gasses are kept.

The merits of Mendeleev’s periodic table are:

  • It is first effective classifications of elements.
  • It also predictedthe discovery of new elements.

They are as follows:

  • It helps for the prediction of new elements.
  • It gives the correct position of the elements.
  • It also helps to describe the simple properties of the elements.

It belongs to the third period. The full name of Na is sodium, mg is magnesium, Al is aluminum, SL is silicon, P is phosphorus, S is sulphur and CL is chlorine. Sodium elements are more reactive because it can easily lose its electrons.

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  • The law "all the physical and chemical properties of elements are the periodic functions of their atomic number " is given by ______.

    heseingberg law


    none of these


    mandeleeves law


    modern law


  • According to Mendeleev the properties of an element are periodic function of their _______.

    atomic mass


    no of electrons


    number of protons


    atomic number


  • Hennery Mosely in 1913 corrected Mendeleev's theory and said the properties of an element are periodic function of their ______.

    atomic number


    number of protons


    atomic mass


    no of electrons


  • How many groups are there in modern periodic table?

    18


    16


    19


    15


  • How many periods are there in modern periodic table?

    7


    6


    9


    8


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DISCUSSIONS ABOUT THIS NOTE

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Bipin dhital

Advantage of mandeleevs periodic table


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why hydrogen is kept in IA group?

modern periodic table


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Define modern periodic law


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