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State the Mendeleev’s Periodic Law

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State the Mendeleev’s periodic law?

The physical and chemical properties of elements are a periodic function of their atomic masses, according to Mendeleev’s Periodic Law.

Mendeleev’s Periodic Table – The periodic table was created by Mendeleev, who organised the elements known at the time in order of increasing atomic masses. Vertical columns termed groups contained elements with comparable qualities. Periods referred to the horizontal rows.

The periodic table’s key properties are:

  • The elements in the periodic table are organised into vertical columns named groups and horizontal rows called periods.

  • The components belonging to the first seven groups have been separated into sub-groups labelled as A and B on the basis of similar qualities. There are eight groups marked by Roman Numerals as I, II, III, IV, V, VI, VII, VIII.

  • Sub-group A in each group is made up of items on the left hand side, whereas sub-group B is made up of elements on the right hand side. Group VIII is made up of nine elements organised into three triads.

  • The periodic chart of Mendeleev has six periods (numbered 1 to 6) or horizontal rows. The fourth, fifth, and sixth periods are split into two halves. In each box, the first half of the elements are placed in the upper left corners, while the second half is placed in the bottom right corners.

Mendeleev’s Periodic Table’s Achievements

Systematic study of the elements – For the first time, Mendeleev organised a significant number of elements into groups and periods. The study of the elements became much more systematic as a result of this.

Mendeleev’s Periodic Table’s Defects

Position of isotopes – The atomic masses of isotopes of the same element differ, yet they all have the same atomic number. Because the periodic table is based on rising atomic masses, all isotopes of a given element must be assigned to distinct positions.

For example: The isotopes of hydrogen with atomic weights 1, 2, and 3 should have been assigned to three distinct locations. However, they have only been assigned to one post.