Question

Write a note about Blocks in periodic table.

Answer 1

The term block has been first used by Charles Janet. there r 4 blocks in periodic table and 1 hypothetical , they r named by there orbital characteristics , i.e s-block p-block d-block f-block and g-block(hypothetical).
 According to the Aufbau principle , the linear order of the "blocks"  in the periodic table is given by the filling order of  "subshell" orbitals , ( i.e 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f............) 

S-BLOCK
The s-block is on the first two group on left side of the periodic table.It mainly consist of  alkali  and alkaline earth metals  respectively.
^Most s-block elements are highly reactive metals
^ The s orbital is a single spherical cloud which can contain only one pair of electrons

P-BLOCK
The p-block is on the right side of the periodic table and includes elements from the 6 groups beginning with group 13 to group 18.P-block elements are identified by the fact that thier valence electrons  are in the p orbital.
^P-BLOCK is  the only block that contains all three types of elements: metals, nonmetals, and metalloids.
^ The p orbital consists of six lobed shapes

D-BLOCK
These elements are also known as the transition metals.The d-block is on the middle of the periodic table and includes elements from group  3 to group 12 . transition elements have variable valance by which they show variable chemical bond.
^The d-orbitals can contain up to five pairs of electrons hence, the block includes ten columns in the periodic table.
^the d-block elements show colour due to d-d transition.

F-BLOCK
The f-block is in the center-left of a 32-column periodic table but in the footnoted appendage of 18-column tables.these r the part of d-block element but due to some different property like radioactivity they r placed in a new block .They are also  called inner transition metals .
^F-block elements are unified by having one or more of their outermost electrons from in the f-orbital but none in the d-orbital or p-orbital. 
^ The f-orbitals can contain up to seven pairs of electrons and  hence, the block includes fourteen columns in the periodic table.

Answer 2

                                      S Block
                                   ----------------

The elements in which last electron enters in to s subshell are called s blocked elements.
eg: 1st group and 2nd group elements. 
The general outer electronic configuration of s block elements is ns¹⁻²

                              P block elements
                            --------------------------

The elements in which last electron enter into outermost p subshell are called p block elements.
eg: Elements from 13th group - 18th group.
The general outer electronic configuration of p block element is ns² np¹⁻⁶

                               d block elements
                            -----------------------------

The elements in which last electron enters into penultimate 'd' subshell are called 'd' block elements.
eg: Elements from 3-12 groups (transition metals).
The general outer electronic configuration of d elements is ( n - 1)d¹⁻¹⁰ ns⁰⁻²

                                F block elements
                              ------------------------------

The elements in which last electron enters into anti-penultimate f subshell are called f block elements.
eg: Lanthanides , Actinides.
The general outer electronic configuraion is  ( n-2 )d¹⁻¹⁴ ( n - 1)d⁰⁻¹ ns²