Q.The lanthanides are placed in the periodic table at
a. left hand side
b. right hand side
c. middle
d. bottom

The f-block consists of two 14-element series placed as separate rows below the main periodic table: the lanthanoid series (₅₈Ce to ₇₁Lu, also called the rare earth elements) and the actinoid series (₉₀Th to ₁₀₃Lr), named after the elements immediately preceding them, lanthanum (₅₇La) and actinium (₈₉Ac), both in group 3. All f-block elements are metals whose last electron fills the inner $(n-2)f$ subshell — since this subshell sits well below the outer 'chemical surface' of the atom, they are called inner-transition elements and show remarkably similar properties within each series. General outer configuration is $ns^2(n-1)d^{0-1}(n-2)f^{1-14}$, with half-filled/fully-filled-subshell exceptions like europium (Z=63, $6s^24f^75d^0$). Elements beyond ₉₂U (uranium) are further called transuranium elements; all are manmade and radioactive.