Chapter 02 periodic table and atomic periodicity or properties

Chapter 02
 periodic table and atomic periodicity or properties:

Modern periodic table:  the table in which elements are arrange in order of increasing atomic number.

Modern periodic law: physical and chemical properties of elements are periodic function of their atomic number.

periodic function: repelition of properties after certain interval of time.

periodicity of elements: the repelition of properties after certain interval of time.

the elements repeats their properties because their valence shell electron configuration repeats.

 eg.   li     2   1
         Na   2   8   1
          k     2   8   8   1

114 elements are known today. for their systematic study they have been classified into group and period.

Group :vertical column are called group there are 18 vertical column. so their are 18 groups.

Periods:  horizontal rows are called periods there are 7 horizontal rows. so their are 7 periods  .

A/c to periods no. of elements

1 period  2 elements
2 period   8 elements
3 period   8 elements
4 period   18 elements
5 period   18 elements
6 period    32 elements
7 period    32 elements

the elements constituent groups 1,2,13,14,15,16,17,18 are called normal elements or representation elements.

the elements of 3,4,5,6,7,8,9,10,11,12 are called transistion elements. because they show transistion (change)  in property.

# from highly +ve   s block to least + ve P block

 Two rows of elements which are placed at the bottom of periodic table are called lanthanoids and actinoids.