If you used Clearing in 2024, how did you find it?

A-Level Chemistry HELP !!!

I do not understand this sub topic in chemistry:

understand how ideas about electronic configuration developed from:
i the fact that atomic emission spectra provide evidence for the existence
of quantum shells
ii the fact that successive ionisation energies provide evidence for the existence
of quantum shells and the group to which the element belongs
iii the fact that the first ionisation energy of successive elements provides
evidence for electron sub-shells

can anyone HELP ?

Reply 1

UtterlyUseless69

Original post by kmat1893

I do not understand this sub topic in chemistry:
understand how ideas about electronic configuration developed from:
i the fact that atomic emission spectra provide evidence for the existence
of quantum shells
ii the fact that successive ionisation energies provide evidence for the existence
of quantum shells and the group to which the element belongs
iii the fact that the first ionisation energy of successive elements provides
evidence for electron sub-shells
can anyone HELP ?

This looks like it’s from the Edexcel syllabus

(i) Atomic emission spectra consist of a unique set of individual lines on a black background. Each line corresponds to a particular wavelength/frequency of light emitted when an electron jumps from a particular quantum shell to another. If there were no quantum shells, then the spectrum wouldn’t consist of a unique set of individual lines and would literally just be a rainbow pattern as any frequency/wavelength of light could be possible because there wouldn’t be anything restricting how far (and therefore how energetic) the jumps are.

(ii) When you are given a list of ionisation energies for a given element (i.e the first, second, third etc), if you spot that there is a large gap between two ionisation energies, it suggests that the next electron is taken from a shell below because the energy required to remove the electron is greater, implying greater attraction from the nucleus. If we take sodium as an example, we can see the second ionisation energy (4562 kJ/mol) is much greater than the first (496 kJ/mol) and that the tenth (141,362 kJ/mol) is much greater than the ninth (28,932 kJ/mol). This suggests that the second electron removed is on a different shell to the first and that the tenth electron is on a different shell to the ninth. Because the first electron must be alone on the outermost shell (since the second is on a different shell), sodium must be in group 1.

(iii) This requires you to be aware of the first ionisation energy trend along a given period (you will usually be taught either period 2 or period 3 or both, but the trend is the same irrespective). You will see a general increase in the first ionisation energies along a period, but the group 3 and group 6 elements will not follow the trend as they will have lower first ionisation energies than their group 2 and 5 counterparts, respectively. This is due to how the p-subshell prefers to be filled (the single p-electron in the group 3 element has a higher energy than the paired s electrons and is more shielded by the other electrons than in the group 2 element and a half-filled p-subshell is more stable than with one of the p-orbitals filled and the other two half-filled, due to the internal repulsion).

Reply 2

UtterlyUseless69

Original post by Scanjo63

Hi, not sure if this is what your looking for but might help: https://www.science-revision.co.uk/A_level_atomic_structure%20_and_line_spectra.html

The above resource offers some useful context to part (i), but goes into a little too much detail for A level. You need not cover the photoelectric effect nor the Rydberg equation.

Reply 3

username5887583

Hi, thanks. I deleted the post

Reply 4

ksmithk

The specification documents are not far off useless. They give you a starting point but often students are left wondering what the hell it's talking about. The atomic emission thing in edexcel is such a minor point, if you missed it out it is unlikely to cost you ANY marks. Just learn the statement that it provides evidence for shells.