A level Chem Question (electronic configuration)
-
Hi all,
I have a question on the electronic configuration of particles, especially when it uses the idea of the stability of 3d^5 4s^1
Some scenarios might be more hypothetical than feasible.
Case 1
What is the final configuration when a particle with initial configuration [Ar] 3d^3 4s^2 gains an electron?
[Ar] 3d^4 4s^2 or [Ar] 3d^5 4s^1?
Case 2
What is the final configuration when a particle with initial configuration [Ar] 3d^6 4s^2 loses two electrons?
[Ar] 3d^6 or [Ar] 3d^5 4s^1?
Too many conflicting approaches on the net, hope to clear things up here.
Thanks in advance!
-
Case 1 :
You're right, this is more hypothetical than feasible, because vanadium is a metal that is only interested in losing electrons to be oxidized to cationic form, not gaining electrons to be reduced to anionic form.
The short answer is : both configurations are possible, depending on other factors (that you needn't concern yourself with at 'A' levels).
However, the more important lesson here is, the exam-smart candidate will :
If this was a P1 qn, then consider both possible, but (if both options are present, then) assume the more direct answer, ie. 3d4 4s2.
If this was a P2 or P3 qn, then intelligently (ie. with explanation) write both configurations in your answer :
"When a particle with initial configuration [Ar] 3d^3 4s^2 gains an electron, it first attains an electron configuration of [Ar] 3d^4 4s^2, which may (or may not) subsequently rearrange itself (as observed in the example of chromium) to have an electron configuration of [Ar] 3d^5 4s^1, by transferring an electron from its 4s orbital, to one of its 3d orbitals, to achieve a more stable half-filled 3d subshell."
Case 2 :
This is pretty straightforward. No rearrangement takes place (as far as the electron configuration of the Fe2+ ion is concerned, when asked at 'A' levels) because Fe2+ is ionic and readily stabilizes itself in other ways (ie. as an alternative to rearranging its electron configuration) such as by forming ionic bonds, and/or coordination complexes (the electrons-in-boxes diagram will include both its own electrons, as well as those of the coordinate dative bonds donated by the ligands).
Bottomline :
At 'A' levels, when removing electrons from d-block elements, remember to just kick away electrons from the 4s orbital (which is further away from the nucleus, thus easier to remove), before removing any electrons from its 3d orbital (which is nearer to the nucleus, thus more difficult to remove).
Originally posted by atomos:Hi all,
I have a question on the electronic configuration of particles, especially when it uses the idea of the stability of 3d^5 4s^1
Some scenarios might be more hypothetical than feasible.
Case 1
What is the final configuration when a particle with initial configuration [Ar] 3d^3 4s^2 gains an electron?
[Ar] 3d^4 4s^2 or [Ar] 3d^5 4s^1?
Case 2
What is the final configuration when a particle with initial configuration [Ar] 3d^6 4s^2 loses two electrons?
[Ar] 3d^6 or [Ar] 3d^5 4s^1?
Too many conflicting approaches on the net, hope to clear things up here.
Thanks in advance!
-
Thanks for taking the effort to type such a concise explanation, especially at this late hour.
To tell the truth, I've taken my A levels many years ago and is now more specialized in O level stuff.
The question came to me as I was looking through some A-level assessment books where the approaches are not consistent and sometimes contradictory (apparently).
Regarding your point on
If this was a P1 qn, then consider both possible, but (if both options are present, then) assume the more direct answer, ie. 3d3 4s2.
I'm assuming you meant 3d4 4s2?
-
Originally posted by atomos:
Thanks for taking the effort to type such a concise explanation, especially at this late hour.
To tell the truth, I've taken my A levels many years ago and is now more specialized in O level stuff.
The question came to me as I was looking through some A-level assessment books where the approaches are not consistent and sometimes contradictory (apparently).
Regarding your point on
I'm assuming you meant 3d4 4s2?
Ahh, you're a tutor, I see. Moving on from just 'O' level students to taking 'A' level students?
Yes, thanks for pointing out that typo.
-
Yup, tutoring secondary level.
Well, couple of reasons keep myself up-to-date on what the A-levels are doing.
1) Avoid over generalising concepts at the O level
2) Advise students on what to expect post-secondary should they be interested in taking chemistry.
3) Potential follow through with students on IP programmes.
As for branching off to take on A-level students, have to think through after I catch up on the demands of A-levels nowadays (which was what led me to this forum).
Its one thing for me to have studied it long ago, need to figure out if I can/can't teach it effectively. hahaha
-
Truth be told, teaching / tutoring 'A' level H2 Chemistry is tougher these days (compared to the past), and increasingly so for the future.
This is largely due to the sudden increase in difficulty of the 2010 and 2011 Cambridge 'A' level papers (rumoured to be a request by MOE to Cambridge, perhaps due to H2 Chem being the only compulsory subject for Medicine, in which thousands of straight A students compete for a mere couple hundred places every year).
Consequently, every JC's internal exam papers are increasingly using more University level data-based questions (for all three branches : physical, inorganic, and organic chemisry) to prepare their students for the 'A' levels.
These days, to teach / tutor 'A' level H2 Chemistry, you'll need to go increasingly more into University level Chemistry materials. Which is a delight for me, but not so much for the average JC student.
-
Unfortunately, H2 Physics did not undergo any major change :(
That's why I'm too bored and have to go teach junior physics olympiad for new challenges :)
-
Originally posted by eagle:
Unfortunately, H2 Physics did not undergo any major change :(
That's why I'm too bored and have to go teach junior physics olympiad for new challenges :)
Cool Eagle!