Question

How can we do the eletornic configuration of the elements above 20?

Answer 1

Take an example of Iron which has atomic number 26.

First calculate the electronic configuration of its sub- shells.

Fe(26): 1s2 2s2 2p6 3s2 3p6 4s2 3d6.

Then, calculate the electronic configuration of its shells.

Fe(26): 2 8 14 2.

EXCEPTION: Chromium (Atomic No.-24) and Copper (Atomic No.-29)

Cr(24): 1s2 2s2 2p6 3s2 3p6 4s1 3d5. Cr(24): 2 8 13 1

Cu(29): 1s2 2s2 2p6 3s2 3p6 4s1 3d10. Cu(29): 2 8 18 1.

For the elements whose atomic number is greater than 21, it will be easy if you calculate the electronic configuration of the sub-shells of that element and then calculate the electronic configuration of the shells.

Answer 2

Electronic Configuration of 20=2,8,8,2