Question

Compare and contrast the arrangement of elements in Mendeléev's Periodic Table
and the Modern Periodic Table.​

Answer 1

Dissimilarities:

★ Mendeleev's Periodic Table:

• Elements are arranged in an order of increasing atomic mass.
• It contain about 63 elements.
• Basic periodic table had total 8 vertical columns, all 1st to 7th are divided into 2 sub - groups.
• Subgroup A and sub - group B is under one group.
• Transition elements were left with other one group.
• Lanthanides and actanoids weren't kept seperately.
• It contain gaps for undiscovered elements.
• Mendeleev's periodic table has no noble gases.

★ Modern Periodic Table:

• Elements are arranged in an order of increasing atomic number.
• Modern Periodic Table contain presently 118 elements.
• It has total 18 vertical columns.
• All groups are separate.
• Transition elements are kept together at one place.
• Lanthanides and actanoids are kept seperately.
• Modern Periodic Table has maintain uniformity.
• Modern Periodic Table has noble gases.

Similarities:

• Both consisted of groups and periods.
• Both failed to gave exact position to H and to accommodate lanthanoides and actanoids in the table.
• Elements are arranged in vertical columns and horizontal rows.
• Metals and non - metals are placed seperately.
• All elements are in same group resembles each other.
• Both have law of periodicity.

Answer 2

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Mendeleev's periodic table

• Elements have been arranged in increasing order of atomic mass
• There are only 8 verticle columns called groups.
• Each groups is subdivided into sub group ‘a’ and ‘b’
• The noble gases were not known at the time of Mendeleev.
• There was no place for isotopes.

Modem periodic table

• Elements have been arranged in increasing of atomic number
• There are 18 verticle columns called groups.
• Each groups are not subdivided into sub groups.
• The noble gases have been placed at the end of table in the separte group (group 18).
• There was no place for isotopes. This problem has been rectified as slots are determined according to atomic number.

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