Question

How are elements arranged in the long form of periodic table.

Answer 1

Modern periodic law:

• Modern periodic law may be stated that the physical and chemical properties of elements are the periodic functions of their atomic numbers.
• Elements are arranged according to increasing atomic numbers. Elements with similar properties are placed together.

Arrangement of Elements in Periodic Table

• The $18$ vertical columns are named for numbers as $1,2,3$. Elements of each group have the same number of valence electrons, so they have similar properties.
• All the inner shells are filled, only the outermost shell is incomplete. It includes group $1,2$ and group $13$ to $17$.
• The outermost shell and the second outermost shell are incomplete. It includes group $3$.to group $12$.
• Elements having atomic numbers from $58$ to $71$ are called lanthanoids. It is placed below the main table.
• Elements having atomic numbers from $90$ to $118$ are called actinoids. It is placed separately at the bottom of the periodic table.
• Elements of Group $18$ have fully occupied valence shells are called inert gases or Noble gases.
• The period number is equal to the number of shells in an atom.

Therefore, From the rules arrangement of elements is done.