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how to identify the group and period of element wen subshell elctronic configuration is given?

how to identify the group and period of element wen subshell elctronic configuration is given?


1 Answers

879 Points
10 years ago

Dear student,

Electronic configuration is the arrangement of electrons in an atom in different shells and sub-shells.After the discovery of the shells and sub-shells,various physical and chemical properties of elements were linked to the electronic configuration.As a result, attempts were made to arrange elements by their  electronic configuration so that their properties would obviously fall in a trend.Subsequently the modern arrangement is evolved wherein elements are organized by atomic number.This is known as modern periodic table.

The modern periodic table has elements arranged according to their electronic configurations.From left to right i.e. in a period,the arrangment is such that each subsequent electron added is to the same shell.



Electronic Configuration is the Period

e.g  Configuration of  Li atomic number. 3,  is  1s2 ,2s1  

Configuration of  Be atomic no. 4,  is  1s2 ,2s2        

Configuration of  B atomic no. 5,  is  1s2 ,2s2,2p1     

Configuration of  C atomic no. 6,  is  1s2 ,2s2 ,2p2      

and so on till Neon,the last element.

This addition of each subsequent electron results in a completely new configuration and as such the chemical properties of  the subsequent element change gradually..At the end of each row, a drastic shift occurs in chemical properties.

Electronic Configuration is the Group

From top to down in a column, a group, each subsequent electron is added to the new shell,but in same sub-shell.                       e.g. In the 1st group,

Configuration of  H atomic number.1,is 1s1  

Configuration of  Li atomic no. 3,  is  1s2 ,2s1      

Configuration of  Na atomic no. 11,  is  1s2 ,s2,2p6 ,3s1    

Configuration of  K atomic no. 19,  is  1s2 ,2s2 ,2p6,3s2 ,3p6,4s1   

and so on till Neon,the last element.

The number of valence shell electrons  in an atom would determine the way it will interact with other  atoms, and therefore determine its chemical properties.

Thus the outermost configuration ,which is responsible for various properties as valency,oxidation states etc. remains same. Hence in a group, the physical and chemical properties are the same. To illustrate,the halogens are strong electronegative elements.

Please feel free to ask your queries here. We are all IITians and here to help you in your IIT JEE preparation.

All the best.

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Askiitians Expert

Sagar Singh

B.Tech, IIT Delhi

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