Elements are placed at the bottom of a Periodic table.
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Solution
Modern periodic table:
The modern periodic table is an arrangement of all the elements known in accordance with their increasing atomic number and recurring chemical properties.
It is a tabular display of 118 chemical elements which consists of horizontal rows called periods and vertical columns are called groups.
All elements in a group have the same number of valance electrons, and in period elements have the same number of electron shells.
Lanthanides and actinides were placed at the bottom of the modern periodic table in different f-block elements.
The lanthanide sequence contains elements 58 to 71 that eventually fill their 4f sub-level.
The actinides are elements 89 to 103 and gradually fill their 5f sublevel.
