Question

Justify the position of f-block elements in the periodic table.

Answer 1

f Block Elements in Modern Periodic Table. The 'f' – block elements are also known by the name of inner transition elements. In these elements, the last electron usually enters the penultimate i.e. (n – 2) f of the orbital. ... In the case of actinides, the differentiating electron enters the 5f orbitals.

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Answer 2

The two series of f-block elements Lanthanides & Actinides are grouped seperately & placed at the bottom of the periodic table, though they belong to the sixth & seventh periods of third group (||| B).

$\: \: \: \: \: \:$ This placement is done on the basis of their similar properties. The properties are so similar that elements from Ce to Lu can be considered as equivalent to one element. In case , if these elements are assigned the usual positions the symmetry of the whole arrangement of the periodic table would be disrupted.