Division of elements : According to the electronic configuration of elements, the elements have been classified into four blocks. The basis for this classification is the entry of the differentiating electron into the subshell. They are classified into s, p, d, and f blocks.
‘s’ block elements :
In the differentiating electron enters into s orbital, the elements belongs to s block.
In every group there are two ‘s’ block elements. As an ‘s’ orbital can have a maximum of two electrons, ‘s’ block has two groups IA and IIA.
‘P’ block elements :
If the differentiating electron enters into ‘p’ orbital, the elements belongs to ‘p’ block.
‘p’ block contains six elements in each period. They are IIIA to VII A and zero group elements. The electronic configuration of ‘p’ block elements varies from to .
‘d’ block elements :
If the differentiating electron enters into (n – 1) d – orbitals the elements belongs to ‘d’ block. These elements are in between ‘s’ and ‘p’ blocks. These elements are also known as transition elements. In these elements n and (n – 1) shells are incompletely filled. The general electronic configuration of ‘d’ block elements is (n – 1) . This block consists of IIIB to VIIB, VIII, IB and IIB groups.
‘f’ block elements :
If the differentiating electron enters into ‘f’ orbitals of antepenultimate shell (n – 2) of atoms of the elements belongs to ‘f’ block. They are in sixth and seven periods in the form of two series with 14 elements each. They are known as lanthanides and actinides and are arranged at the bottom of the periodic table. The general electronic configuration is (n – 2) .
In these shells the last three shells (ultimate, penultimate and antepenultimate) are completely filled. Lanthanides belongs to 4f series. It contains Ce to Lu. Actinides belong to 5f series. It contains Th to Lr.
Advantages of division of elements :
As a result of this classification of elements were placed in correct positions in the periodic table. It shows a gradual gradation in physical and chemical properties of elements. The metallic nature gradually decreases and non – metallic nature gradually increases from ‘s’ block to ‘p’ block. This classification gave a special place for radioactive elements.