How are the elements divided into s, p, d and f – blocks in the Modern periodic table ?

Explanation

Depending upon the entering of differentiating electrn into the atomic orbitals, the elements of long form of periodic table are divided into four blocks. They are s, p, d and f-blocks.
s-block : The elements, in which the differentiating electron enters the s- sub-level are called s-block elements.
In this block, there are two groups. They are IA and IIA.
The valence electron configuration of elements of IA group is `ns^(1)` and that of IIA is `ns^(2)`
p-Block : The elements in which the differentiating electron enters the p- sub-level are called p-block elements. In this block, there are six groups. They are IIIA, IVA, VA, VIA, VIIA and .0.. The valence electron configuration of the elements of these groups varies from `ns^(2) np^(1)` to `ns^(2) np^(6)`
d-Block : The elements in which the differentiating electron enters into d- sub-level are called d-block elements. In this block, there are then groups. They are IIIB, IVB, VB, VIB, VIIB, VIII, IB, IIB. The general outer configuration of d-block elements is `(n - 1)d^(1 - 10) ns^(1-2)`. These elements are also known as Transition elements.

f-Block : The elements in which the differentiating electron enters into f-orbital are called f-block elements. In this block, there are 14 groups. They have no designation. Their general outer configuration is `(n - 2) f^(1-14) (n - 1)d^(0 - 1) ns^(2)`. The f-block elements are arranged separately at the bottom in two rows. The elements of first row are called lanthanides and in these elements the valence electron enters into 4f orbital. The elements of second row are called actinides and in these elements the valence electron enters into 5f orbital. All the f-block elements are also known as Inner Transltion elements.
Advantages of this type of classification :
1. There is a good correlation between the properties of the element and its position in the periodic table.
2. A gradual gradation in the physical and chemical properties of elements is clearly observed.
3. As we go grom elements of s-block to elements of p-block, a gradual decrease in the metallic nature and a gradual increase in the non-metallic nature is observed.
4. Special position for radioactive elements is given.
Anomalies : There are two anomalies
(i) Helium : He has `1s^(2)` configuration. So it belongs to .s. block. But it is included in inert elements of p-block. But this is justified for two reasons.
(a) It has completely filled valence shell `(1s^(2))` like the inert gases.
(b) Because of such configuration, it exhibits characteristic properties of the inert gases.
(ii) Hydrogen : Its configuration is `1s^(1)`. So it can be placed in `1^(st)` group along with alkali metals. But like the halogens `(ns^(2) np^(5))`, it is short of 1 electron for the inert gas structure.