Question

why are lanthanides and actinides places separately in the bottom of the periodic table if if they are inserted in the table what would happen between a neutral atom and its a cation cations which has bigger size why

Answer 1

Lanthanoids and actinides are inner transition elements characterized by filling of f-orbital. And to keep the shape of periodic table, they were placed seperately in bottom of periodic table in f-block.

Cation has smaller size cz removing an electron would result in increasing average nuclear charge experianced by valence electrons. Hence, atom shrinks.