How to write condensed electron config?

Question

I having problem understanding the steps to writing the condensed electron config. I would appreciate an explanation.

for example :1s2 2s2 2p6 3s2 3p6 4s1---19K

Answer 1

Condensed electron configuration uses the core configuration of the

highest inert gas lower in atomic number than the element specified.

In your example, argon is the inert gas just below potassium, and we

know the configuration of Ar is 1s2,2s2,2p6,3s2,3p6.  We can just

abbreviate that part as [Ar] so the configuration of potassium can be

more simply shown as [Ar] 4s1.

Hope this answers your question.

Answer 2

The electronic configuration of Ar ( noble gas) is

1s2, 2s2, 2p6, 3s2 . 3p6

so the condensed electronic configuration of K is :

[Ar] 4s1