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modern periodic table?

Moseley modified Mendeleeff's periodic table and stated that the basis of classification of elements be according to increasing atomic numbers and not atomic weights since physical and chemical properties of elements ,depend on the number of electrons and their arrangement .
Atomic number is equal to the  number of electrons in the energy shells of an atom hence atomic number is the fundamental property of an element .
Modern periodic law -arrangement of elements in the periodic table is thus based on the periodic law which states that physical and chemical properties of elements are periodic functions of their atomic number .

Salient features of modern periodic table  :

Classification -Periodic table based on the basic fundamental property -atomic number 
Position  -Correlates position of an element with its -electronic configuration.

Methodological arrangement : Arranges elements in increasing order of atomic numbers in seven horizontal rows called periods and eighteen vertical columns called groups .

Periods  : Completion of each period is logical ,since each period begins with an element having completely filled outer shell .
A transition from metallic to non metallic character is thus seen across a period .
Groups   : Each vertical columns accommodates elements with the same outer electronic configuration ,hence having similar properties .

18 vertical columns consists of groups 1 to17 and 18 (zero group  )

-Group  1,2 and 13 to 17 (IA to VII A ) are called normal elements 
-Groups 3 to 12  (I B to VII B  and VII are called transition elements 
Groups 18 (zero) at extreme right contains 'noble gases or inert gases 
Separation of elements   : Reactive metals       : are placed in group 1 (IA )  and (IIA )
                                       Transition elements :  (metals are placed in the middle )
                                       Non -metals           : are placed in the upper right corner of the                                                                         periodic table 

Periodicity of elements  :  Gradual change in properties -is seen with -increase in atomic number in the periodic table 
Periodicity in properties -that is recurrence in properties are seen with elements belonging to the same  sub group in the periodic  table .
-after a difference of 2,8 18 or 32  in atomic numbers due to recurrence of similar valence shell electronic configuration .


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