C1 how do ionisation energies provide evidence for existance of charartic energy leve

levels of s,p,d orbitals ?? and also existance of quantum shells?

Thanks!!!

Reply 1

if you look at the 1st ionisation energies across period 2 you will see that the general trend is that as you move across (Li -> Ne), the ionisation energies increase
evidence for s,p, orbitals, however, is provided by results breaking from this 'trend'
the first of these anomalous results is between Be and B, because although you would expect B to be higher than Be, it is in fact lower (i.e. easier to ionise), due to the fact that the 2s subshell is full, and that Boron's outermost electron is now in the 2p subshell. this means that Boron's outer electron has a higher energy level and is hence easier to remove than Be's outer electron in the 2s subshell. this provides evidence for the p orbitals

the second of these anomalous results is between nitrogen and oxygen
oxygen has 6 electrions in its outer shell, where nitrogen has 5
both elements have 2 of their electrons in the 2s orbital, and the rest in the 2p orbital
taking into account the fact that the electrons in the p orbital go around in pairs when forced to, and knowing that nitrogen has 3 electrons in it (one in each of the quantum shells), we can work out that when oxygen has its 6th electron, it will be forced to pair up with one of the 3 already in the 2p orbital. thereby electron repulsion causes it to be easy to remove from the 2p subshell, as the paired up electrons will be repelling each other

sorry, not sure how i can explain it any better
if you're stuck try www.chemguide.co.uk
or get a revision guide ;p

Reply 2

Mushu

LondonBoy

levels of s,p,d orbitals ?? and also existance of quantum shells?

Thanks!!!

I'm to tired to type (It's late lol) but if ur still unsure about it, pm me and and I will do it :smile:

Sorry for being lazy! Oh on second thoughts Ill do it quick:

Evidence for S subshell is shown by the drop in ionisations energies between gp 2 + 3. This is because the outer electrons of a gp 2 element is in a s-subshell, wheras the outer electrons of a gp 3 element is in a p subshell, which is further away from the nucleus + more shielded. Therefore there is a decreased nuclear attraction for the outer electrons in a p-subshell meaning decreased ionisation energies, hence the drop between gp 2 + gp 3.

Evidence for P subshell is shown by a drop in ionisation energies between groups 5 + 6. Take the example, Nitrogen (gp 5) and Oxygen (gp 6). Nitrogen has 3 p electrons singly occuping its p - atomic orbital, wheras Oxygen has 4 p electrons, resulting in one of the p atomic orbitals having 2 p electrons. Because the 2 electrons are together, there is repulsion due to them having the same negative charge. Therefore if you needed to remove an electron form either Nitrogen or Oxygen, it would be easier to remove it from the Oxygen due to the repulsion. Therefore there is a drop in ionisation energies at Oxygen (so between gp 5 and 6).

If your doing edexcel, you only need to know that the evidence for a D subshell is the almost constant ionsation energies from Scandium to Zinc. They wouldnt expect you to know the reason for this.

As for quantam shells ? I dont think you need to know this for edexcel...?

Best of luck with chem and pm me about any queries :smile:

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