*(a) -block elements:* An element in which the outermost (differentiating) electron of its atom belongs to -orbital of valence shell is called *-block elements. Kept in left hand side of the periodic table, group I & II (or IA & lIA).
(b) p-block elements: An element in which the outermost (differentiating) electron of its atom belongs to p-orbital of valence shell is called p-block elements. Kept in right hand side of the periodic table, group 13 to 18. Elements in group 18 are called Aerogens or Noble gases. General electronic configuration of p-block elements is ns2 np1-6. Both * and p block together is called representative or normal elements.
(c) d-block elements:The atom of an element in which outermost (differentiating) electron enters to d- sub shell of pen ultimate (n-1) shell is called d-block elements. Kept at middle (between * and p block elements) portion of the periodic table, group 3 to 12.
(d) f-block elements: An element in which outermost (differentiating) electron of its atom enters to f-sub shell of anti-penultimate (n-2) shell is called f -block elements. Placed separately at the bottom portion of the periodic table. General electronic configuration of f-block elements is (n – 2) f1-14 (n-l)d1ns2.
