Question

How are inert gas cores used as a shorthand for electronic configuration?

Answer 1

Use the configuration of the inert gas core as a basis...........

Explanation:

For atomic lithium we have a configuration of `1s^(2)2s^(1)`. We COULD use the known configuration of helium to write `[He]2s^1`. All the chemistry is going to occur outside the inert gas core........

And then we go to neon, `Z=10:1s^(2)2s^(2)2p^(6)`, and then sodium, `Z=11:1s^(2)2s^(2)2p^(6)3s^1`. We have a valence electron tacked onto an inert gas core, i.e. `[Ne]3s^1`. How does you represent magnesium? How about potassium?

Do you get the picture?

Edited for a mistake. With all these problems you SHOULD have your Periodic Table in front of you.