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Classification of elements

Classification of Elements : The chemical properties of all elements depend upon the electronic configuration. Classification of elements is done upon the basis of complete and incomplete electron shells and chemical properties, the elements are classified into four types.

Type – I (Inert gas elements) :

All the elements with an electronic configuration ns^{2}\; np^{6} including He belongs to this type. nth shell of those elements are completely filled.

The element shows chemical inertness due to completely filled shells and hence they have extra stability. Because of their stability, they are chemically inactive.

e.g. : He, Ne, Ar, Kr, Xe and Rn.

Type – II (Representative elements) :

Except inert gases, the remaining elements of s and p – blocks are called representative elements. All the elements with an electronic configuration ns^{1} to ns^{2} \;np^{5} excluding. He comes under this type. These are atoms in which all except the outermost shells are complete. Elements of this type enter into chemical combination by loosing, gaining or sharing electrons to get stable inert gas configuration. Many of the metals, all non – metals and metalloids come under this type. Chemically these elements are reactive.

Type – III (Transition elements) :

All the elements with an electronic configuration (n - 1)\;d^{1-9} \;ns^{1 \;or \;2}  belongs to this type. Atoms in which the two outermost shells are incomplete. These elements show variable oxidation states, form complex ions and coloured ions. The electronic configuration of d – block elements is (n - 1) \;d^{1 - 10} \;ns^{1-2}. Small size, high nuclear charge and unpaired ‘d’ orbitals impart characteristic properties to be transition elements.

Type –IV (Inner transition elements) :

All the elements with an electronic configuration (n- 2)\; f^{1-14} (n - 1) d^{0,1} ns^{2} belongs to this type. Atoms in which three outermost shells are incomplete. Lanthanides and Actinides belong to this type.