Inner Transition elements

Explanation

(i) Elements placed in two separate rows at the bottom of the periodic table are called inner transition elements.
(ii) They include two series of elements: Lanthanide series and Actinide series. They belong to f-block elements of Modem Periodic table.
(iii) 14 elements with atomic number 58 to 71 (Cerium to Lutetium) are called lanthanides. These elements are placed along with lanthanum (La= 57) in group 3 and period 6 because of very close resemblance in properties between them.
(iv) 14 elements with atomic number 90 to 103 (Thorium to Lawrencium) are called actinides. These elements are placed along with actinium (Ac= 89) in group 3 and period 7 because of very close resemblance in their properties.
(v)They have last three shells incompletely filled.
(vi) All these elements are metals.