how does the electronic configuration of an element relate to its position in moden periodic table ?explain with an example

plz answer..................

The distribution of electrons into different shells of an atom is called electronic configuration.  The element's location in the Periodic Table reflects that the last electron is entered in last shell. This shows that there is direct connection between the electronic configuration of the elements and the long form of the Periodic Table.

For example

The number of electrons present in outer most shell of an element decide its group while the number of shell used to define configuration defines period of an element for example:

13Al = 2 8 3

Since in above configuration, three  shell are used therefore it is a third period element while 3 electrons are present in last shell therefore belongs to third group element.

For the element in the range of 3 to 12 belong to d block elements, can be determined as follows by example:

26Fe – 1s2 2s2 2p6 3s2 3p6 4s2 3d6

Period: Check the last shell, its 4s2, hence belong to 4 period

Group: Add the total number of electron present in 4s2 and 3d6 = 2+6 = 8.

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Elements are arranged in Modern Periodic table acc. to Auf Bau Principal which says that elements are added in increasing order of energy levels starting with the lowest energy level .

for ex. Na  is the element of Ist grp. and its electronic configuration is 1s2 2s2 2p6 3s1 

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