Question: lanthanides and actinides are placed in separate rows at the bottom of periodic table?
Answer: The lanthanides include elements 58 to 71 (fill out the 4f subshell) and the actinides include elements 89 to 103 (fill out the 5f subshell). The reason why inner-transition metals are located at the bottom of the periodic table, separated from the rest is because they all fill the f-block.