Inner-Transition Elements.

1.	Inner-Transition Elements.
Answer» SOLUTION :(i) Elements PLACED in two separate rows at thebottom of the periodic table are called innertransition elements. (ii) They include two series of elements: Lanthanideseries and Actinide series. They belong to f-blockelements 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 veryclose 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 period7 because of veryclose resemblance in their properties. (v)They have last three shells incompletely filled. (vi) All these elements are metals.

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