Question

Lanthanides and actinides are placed in separate rows at the bottom of the periodic table. Give the reason for this arrangement.

Answer 1

The systematic arrangement of elements into groups and periods on the basis of similarities in chemical properties and in the order of their increasing atomic number is called modern periodic table.

The elements from atomic numbers 58 to 71 are called Lanthanides. It consists of 14 elements.

The elements from atomic numbers 90 to 103 are called Actinides. It consists of 14 elements.

Lanthanides and Actinides are placed in separate rows at the bottom of the periodic table because they are too wide and occupy lots of space. So to conserve space, Lanthanides and Actinides are placed down the periodic table.