User:Harshitha Sheshadri

Introduction
Periodic table is a table where all known elements are classified according to their physical and chemical properties. We can get basic information like atomic number, atomic mass number, name of the element, symbol of the element. There were many attempts by many scientists to classify the elements. At present we are using modern periodic law proposed by Henry Moseley to arrange the elements. Modern periodic table contains 7 horizontal rows called periods and 18 vertical columns called groups.

Classification into blocks

 * 1)  	s-block elements [ns1-2] -The differentiating electron enters s-orbital of outermost shell. Group 1 and group 2 elements comes under this block.
 * 2)  	p-block elements [ns2np1-6] -The differentiating electron enters p-orbital of outermost shell. Groups 13 to group 18 elements belongs to this block.
 * 3)  	d-block elements [ns1-2(n-1)d1-10] -The differentiating electron enters d-orbital of outermost shell. Group 3 to group 12 elements belongs to this block.
 * 4)  	f-block elements [ns1-2(n-1)d1-10(n-2)f1-14] -The differentiating electron enters f-orbital of outermost shell. Two separate horizontal table below the periodic table called as lanthanides and actinides belongs to this block.

Classification based on configuration

 * 1) 	Inert gas elements-Elements in which outermost s and p orbitals are completely filled. General electronic configuration is ns2 np6.
 * 2) 	Representative elements-Elements in which the outermost shell is incompletely filled. General electronic configuration is ns1-2,ns2 np1-5.
 * 3) 	Transition elements-Elements which have incompletely filled outermost and penultimate shells. General electronic configuration is ns1-2 (n-1)d1-9.
 * 4)       Inner transition elements- Elements in which three outermost shells(ultimate,penultimate and anti penultimate shells) General electronic configuration is ns2 (n-1)d0-1(n-2)f1-14.