[Rattlethesnake]

I've got a simple problem but for some reason I can't get it correct. Maybe I've misunderstood the reasoning behind it.

I basically need to find the first excited state configuration of Be, O and Ne.

Now I thought it was just a matter of moving up to the next orbital, ie:

from [He]2s2 [He]2s2 2p4 and [He]2s2 2p6   I assumed it would be enough to move one step higher onto:

[He]2s2 2p1 [He]2s2 2p5 and [He]3s1

but this didn't work out

I then assumed I would have to go the next energy level:

[He]2s2 2p1 [He]3s1 and [He]3s1

Again, it didn't work.

Any idea what I'm doing wrong?

[Mitch]

For your Be example you have 2 electrons in the ground state, and 3 electrons in the excited state.

[Rattlethesnake]

Thanks for your reply Mitch.

Ok, I never really thought about the number of electrons, but of course it doesn't change.

I've referred to the theory once again and this time here are my answers:

Be: [He]2s1 2p1
O: [He]2s1 2p5
Ne: [He]2s2 2p5 3s1  (I also tried 2s1 2p6 3s1)

And apparently it's still wrong.

Does anyone see any mistakes here?

[ARGOS++]

Dear Rattlethesnake,

To answer your question you must first find out, what are the Excited States ( = LUMO) and what are the “highest” Ground State ( = HOMO) of all your elements. And here it is where you did the mistakes.

To help you I have added a simple graph about the Electron-States of the Elements and their corresponding relative Energy.
Now you can ease see, that for ALL Elements their p-Electrons are of higher Energy as their s-Electrons. So you will for Neon not excite an s-Electron, as its p-Electrons are in the real HOMO State.
I think that it is now easy to correct all  the Excited States to what they have to be.

Good Luck!
                    ARGOS⁺⁺

[Mitch]

Be looks fine to me.

[Rattlethesnake]

Mitch thanks a lot for your help, again.

I've found the correct answer now. Be and Ne were correct.

However, my mistake was with O

Ground state: [He]2s2 2p4

Now, the excited state requires an electron in a HIGHER energy state, so we should be placing one of the p electrons in a higher level. Therefore:

[He]2s2 2p3 3s1