Permitted electron energy level diagrams

Factual Questions
1

I’m trying to catch up four weeks of missed work in physics now, and it’s a bummer, since I only have the book at the moment, and my physics teacher who deals with this module is away.

This question is really really simple and stupid, but I want to check that I’ve got this right before I make my notes and start revising for my exam in the summer.

Right, in an electron permitted energy level diagram, there are horizontal lines with energy values next to them that represent the different atomic levels that the electron could be on for the given element.

The values start with ones close to zero at the top, and increasing as you go down the diagram.

I just want to check, do the horizontal lines with the highest values next to them represent the atomic levels closest or farthest from the nucleus?

[guessing with rudimentry a-level chemistry]
I’m not entirely sure of this, but elements with valence electrons in higher atomic levels have lower 1st Ionization energies than ones with their valence electrons in lower atomic levels. This must mean that the electrons in the higher atomic levels have lower energies than those in the lower ones. Therefore, the horizontal lines with the highest values must represent the lowest atomic levels.
[/guessing with rudimentry a-level chemistry]

I dont really know if my logic works, but I tried, give me that.

I’m sorry this is another “I need help with my homework” thread, the type which was recently complained about. However, I have given (as I’ve always done) what I think might be the answer, and this is a last resort so I can get the A I really, really need.

Okey dokey, sorry if this is a stupid and lame question, but I really need the answer.

Cheers, Harry

2

By convention, lower energy is more stable.

3

I understand that lower energy is more stable, but I’m not sure if that really answers my question. It’s probably just me being dumb and not getting how you’re helping me.

What I’m asking is “is my rather foolish attempt at an answer with chemistry” actually correct?

4

I’m not completely sure I understand your idea.

Ionization energies increase as you remove additional electrons because the attractive force of the nucleus remains the same while the repulsive force from the other electrons decreases (because there are fewer other electrons). This doesn’t really relate to electron energy diagrams.

If your energy diagrams are like the ones I used to use, then the numbers next to the different levels would be in negative eV. So the “small” numbers near the top are actually larger than the “large” numbers near the bottom.

This means that the lower levels are lower energy than the higher levels. The “lower energy” bottom levels are the ones closest to the nucleus and the lowest energy.

I hope this helps.

5

Sorry, I think I’ve made myself a bit unclear when explaining what I mean (well, not I think, but I have).

I was trying to say how the first ionisation energy for Francium is less than Hydrogen. This is because the valence electron for Francium is shielded from the nucleus by the closer ones. However, my argument doesn’t really work, since ionization energies are not lower because of the electron having less energy itself.

Right, for now, can we please ignore my original argument since I’ve realised how foolish it is, because ionization is easier for bigger atoms due to charges, nor energies of electrons. I feel really stupid for thinking such a stupid idea, and I’d rather that no-one teases me about it if it’s not too much to ask now. Never mind.

Zigaretten, the diagrams in my textbook are in negative eV too, and I can never use the right terms when describing negative numbers unfortunately. A bit of a sidetrack, but can I use ‘greater than’ or ‘less than’ to describe negative numbers as if they were positive?

I get what you’ve said now, and that’s all I really needed to know, so i’ve changed my notes accordingly. I guess I could have used my knowledge of semi-conductors and LEDs (and my physics teacher’s impression of an electron jumping up and down when it absorbs or gives off a photon).

Right, thanks very much for help all.

A special thanks to zigaretten, since you’ve helped my in all my homework troubles so far. Up to now, they’ve only been chemistry, but learning all this work from a textbook that’s not-so-great to teach yourself from is tricky, so this was my first downfall in physics.

6

It sounds like you are satisfied by the answers so far, but I typed this before I absorbed the quote above so I’m posting anyway…

I try to avoid these diagrams if at all possible, but in my world these diagrams represent the amount of energy required to ionize the electron. For an electron deep in the quantum well in the ground state, it has a negative potential energy with a large absolute magnitude corresponding to the amount of energy (work) that would be required to free the electron from the well. As the electron climbs partially out of the well (by absorbing energy from an outside force, typically a photon), the energy levels become more closely spaced and the amount of energy required for ionization decreases.

7

Strictly speaking, “less than” means “to the left of on the number line”. So -2 is less than -1. But this could get confusing. Unless you’re in the company of mathematicians or other technical sorts, I would recommend, instead, that you refer to magnitudes of numbers, which is how far the number is from zero. So -2 is larger in magnitude than -1.