The Student Room Group

Chemistry Orbitals/Shells/Subshells PLEASE HELP

I really need someone to explain this clearly for me! I don't understand how/why the elements in S block can only hold 2 electrons (in which shell?), and can P hold more than 2 but less than 10? And I don't understand the configuration format like 1s2,2sp,ps1,3p2 or something like that! And are these spdf within the shells? and are the subshells within the spdf?? so confusing!

Scroll to see replies

Reply 1
Original post by Perfection Ace
I really need someone to explain this clearly for me! I don't understand how/why the elements in S block can only hold 2 electrons (in which shell?), and can P hold more than 2 but less than 10? And I don't understand the configuration format like 1s2,2sp,ps1,3p2 or something like that! And are these spdf within the shells? and are the subshells within the spdf?? so confusing!


http://www.chemguide.co.uk/atoms/properties/atomorbs.html
Go to this page because it sounds like you're not sure of anything.
Each orbital can hold one or two electrons. the p-orbital holds up to 6 because there are three separate p-orbitals which are at right angles to one another.
spdf are sub shells

do you have the ocr a level textbook? the configuration format is quite hard to explain on here
(edited 7 years ago)
Original post by Perfection Ace
I really need someone to explain this clearly for me! I don't understand how/why the elements in S block can only hold 2 electrons (in which shell?), and can P hold more than 2 but less than 10?

Write have you heard of these things called orbitals? Well if not then they are the space or place that an electron is likely to occur. Each orbital can hold up to two electrons.

The s sub shells only have 1 orbital and so can only hold 2 electrons.
The p sub shells have 3 orbitals and so can hold up to 6 electrons as 2*3=6
The d have 5 orbitals and so you guessed it hold up to 10 electrons. Etc.


And I don't understand the configuration format like 1s2,2sp,ps1,3p2 or something like that!

When there is only one electron it goes to the first she'll. Particularly the 1s sub shell. After this subshell is full electrons then go to the next shell (2nd shell). So then electrons start filling up with the 2s shell. Then when that is full it's still on the 2nd shell but they will now go to the 2p shell.

The order is usually
1s 2s 2p 3s 3p 4s (this may seem weird as you expect it to go to 3d first but it doesnt) 3d. I don't think you need to know the rest.



And are these spdf within the shells? and are the subshells within the spdf?? so confusing!


So you have regular electron shells like you learned at gcse. But the spdf are the sub shells with in the shells.

Think of it like this there are 4 boxes and each box has a compartment.

One type of compartment is small another type is slightly bigger ,the other type is even bigger and the last type is the biggest.

To fill up the box you have to start filling up from the smallest which can only hold a small amount. Then the next which can hold more but still has a certain amount and so on.

I know it's confusing but if you keep trying to understand it and try and get people who know what it's about to explain then eventually you will get it.

Sorry if my information is wrong but this is how I understand them.



Posted from TSR Mobile
Original post by B_9710
http://www.chemguide.co.uk/atoms/properties/atomorbs.html
Go to this page because it sounds like you're not sure of anything.


Original post by happiness12
Each orbital can hold one or two electrons. the p-orbital holds up to 6 because there are three separate p-orbitals which are at right angles to one another.
spdf are sub shells

do you have the ocr a level textbook? the configuration format is quite hard to explain on here


I've got the textbook but it is still confusing! Like, is an orbital a shell? does that mean a p-orbital is a p-shell? and are there further p-orbitals within in the p-orbital which is in the first shell??? and what exactly are sub shells? smaller shells in original shell?

Original post by GabbytheGreek_48
So you have regular electron shells like you learned at gcse. But the spdf are the sub shells with in the shells.

Think of it like this there are 4 boxes and each box has a compartment.

One type of compartment is small another type is slightly bigger ,the other type is even bigger and the last type is the biggest.

To fill up the box you have to start filling up from the smallest which can only hold a small amount. Then the next which can hold more but still has a certain amount and so on.

I know it's confusing but if you keep trying to understand it and try and get people who know what it's about to explain then eventually you will get it.

Sorry if my information is wrong but this is how I understand them.



Posted from TSR Mobile


Ummmm, that's actually kind of a good explanation.....is there more to it? And what type of questions would it ask? Eg, Do the electronic configuration for Carbon, how would I do that??
Reply 5
Original post by Perfection Ace
I've got the textbook but it is still confusing! Like, is an orbital a shell? does that mean a p-orbital is a p-shell? and are there further p-orbitals within in the p-orbital which is in the first shell??? and what exactly are sub shells? smaller shells in original shell?



Ummmm, that's actually kind of a good explanation.....is there more to it? And what type of questions would it ask? Eg, Do the electronic configuration for Carbon, how would I do that??


Each shell is made up of sub shells which can be (s, p, d or f sub shells depending on electron configuration), each subshell is made up of orbitals, and each orbital contains 2 electrons. In an s subshell, there is only 1 orbital, in a p subshell, there are 3 orbitals, 5 orbitals in d subshell.
Original post by B_9710
Each shell is made up of sub shells which can be (s, p, d or f sub shells depending on electron configuration), each subshell is made up of orbitals, and each orbital contains 2 electrons. In an s subshell, there is only 1 orbital, in a p subshell, there are 3 orbitals, 5 orbitals in d subshell.


Alright, so subshells: S P D or F - cool. What do you mean depending on electron configuration? Like how many shells it has?
How do I know how many orbitals are in the sub shells? Does the amount of orbitals in each subshell change or anything or does it remain 1,3,5. I remember my teacher telling me something about the 1st shell can only hold 2 electrons, 2nd can hold 8, 3rd can hold 16, 4th can hold 32....? :frown:
Original post by Perfection Ace
Alright, so subshells: S P D or F - cool. What do you mean depending on electron configuration? Like how many shells it has?

Yeah well an elements or atom with one shell is only going to have an s sub shell

An atom with two shells
The first shell will be the s sub shell and the second will be an s and a p subshell

An atom with three shells
First shell will be the s sub shell
The second shell will have the s and p sub shell
And the third will have the s p and d sub shell

And so on


How do I know how many orbitals are in the sub shells? Does the amount of orbitals in each subshell change or anything or does it remain 1,3,5.
The amount is always the same for the sub shells as far as I know and yes the orbitals are 1,3,5 the f sub shells have 7 orbitals (so 14 electrons) . And how do I know well that's what I learnt that's what I was told idk how they proved it but you don't need to know that.


I remember my teacher telling me something about the 1st shell can only hold 2 electrons, 2nd can hold 8, 3rd can hold 16, 4th can hold 32....?

The 1st shell holds two yes because it only has 1 s sub shell (so only 2 electrons.)
The 2nd has 8 because it has a s sub shell ( 2 electrons) and a p sub shell (6 electrons) so 6+2 =8 . And well for the 3rd I think it's 18 as you have a s (2 eletrons) a p (6 electrons) and a d (10 electrons) 2+6+10=18.

Hope this clears things up a bit (and not make things more complex) sorry I'm not good at explaining.


:frown:




Posted from TSR Mobile
Reply 8
A shell contains sub shells (s,p,d,f) and within these subshells are orbitals (you only need to know about s, px, py, pz I believe). Each orbital can hold two electrons of opposite spin. Elements in the S block have their outermost electron in an S subshell, likewise for P, D or F block elements.

An example of a P block element would be Chlorine, it's outermost electrons are in a P subshell which contains 5 electrons (as it is 5 along the p block on the periodic table). It's electron configuration would be 1s2, 2s2, 2p6, 3s2, 3p5. If you look on the periodic table you can easily see the very last of an elements electron configuration. i.e Chlorine is in period 3, 5th along the P block, hence it's outermost subshell is 3p5, and all subshells before this are also filled (some exceptions to this rule, but not needed for AS).

As a shell consists of multiple sub-shells the maximum number of electrons is given by 2n^2, where n is the shell number;
n=1, 2
n=2, 8
n=3, 18
n=4, 32
As already mentioned, any orbital can only hold 2 electrons, but each subshell has a different number of orbitals, so an S subshell has an S orbital only, a P subshell has 3 P orbitals all at right angles to eachother, D subshell has 5 orbitals (shape/location not needed)

Hope this clears up most questions you had but I'm glad to help if there's anything extra.
(edited 7 years ago)
Original post by JN17
A shell contains sub shells (s,p,d,f) and within these subshells are orbitals (you only need to know about s, px, py, pz I believe). Each orbital can hold two electrons of opposite spin. Elements in the S block have their outermost electron in an S subshell, likewise for P, D or F block elements.

An example of a P block element would be Chlorine, it's outermost electrons are in a P subshell which contains 5 electrons (as it is 5 along the p block on the periodic table). It's electron configuration would be 1s2, 2s2, 2p6, 3s2, 3p5. If you look on the periodic table you can easily see the very last of an elements electron configuration. i.e Chlorine is in period 3, 5th along the P block, hence it's outermost subshell is 3p5, and all subshells before this are also filled (some exceptions to this rule, but not needed for AS).

As a shell consists of multiple sub-shells the maximum number of electrons is given by 2n^2, where n is the shell number;
n=1, 2
n=2, 8
n=3, 18
n=4, 32
As already mentioned, any orbital can only hold 2 electrons, but each subshell has a different number of orbitals, so an S subshell has an S orbital only, a P subshell has 3 P orbitals all at right angles to eachother, D subshell has 5 orbitals (shape/location not needed)

Hope this clears up most questions you had but I'm glad to help if there's anything extra.


OHHHH, so that's where the 2*1=2, 2*3=6, 2*5=10. Thankssss, im just confused as to like how do I know/do the electronic configuration? How do I know how many electrons are in each shell for an element eg Titanium or something?? and if in the 3rd shell, there's 8 or 16, will it be 3s2, 3s2, 3s2, 3s2? When do i put the p in?
Original post by Perfection Ace
OHHHH, so that's where the 2*1=2, 2*3=6, 2*5=10. Thankssss, im just confused as to like how do I know/do the electronic configuration? How do I know how many electrons are in each shell for an element eg Titanium or something?? and if in the 3rd shell, there's 8 or 16, will it be 3s2, 3s2, 3s2, 3s2? When do i put the p in?


The third shell has 18
2 from the s sub shell 6 from the p sub shell and 10 from the d sub shell.

However the 4s shell fills up before the 3d so when writing configurations it usually goes

3s2 3p6 4s2 then 3d10


Posted from TSR Mobile
Original post by GabbytheGreek_48
The third shell has 18
2 from the s sub shell 6 from the p sub shell and 10 from the d sub shell.

However the 4s shell fills up before the 3d so when writing configurations it usually goes

3s2 3p6 4s2 then 3d10


Posted from TSR Mobile


Thanks....I think I'm starting to get it..... why can I not do 3s2 3s2 3s2 3s2? Instead of 3s2 3p6? There's still 8?? I think you are explaining well but I just can't force my brain to comprehend :s-smilie: AS chemistry is soooo hard
Reply 12
Original post by Perfection Ace
Thanks....I think I'm starting to get it..... why can I not do 3s2 3s2 3s2 3s2? Instead of 3s2 3p6? There's still 8?? I think you are explaining well but I just can't force my brain to comprehend :s-smilie: AS chemistry is soooo hard

There is only one S orbital per shell, hence only one '3s...' available to fill electrons. Electrons always fill from the lowest energy level subshells first (ignoring the 3d&4s exception).
For titanium like you mentioned, it is in the d block, 3rd period and 2 along, so its outermost subshell is 3d2. Working backwards (filling everything before 3d2), we get 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d2. I'd imagine the reason 4s2 is there can be confusing so I'd advise you to see the picture here http://www.mikeblaber.org/oldwine/chm1045/notes/Struct/EPeriod/Struct09.htm
(idk how to attach images). If you were to label titanium on that image (2nd in from the left of 3d), you'd fill every subshell up to that point working from top left to bottom right of the table.
Original post by Perfection Ace
Thanks....I think I'm starting to get it..... why can I not do 3s2 3s2 3s2 3s2? Instead of 3s2 3p6? There's still 8?? I think you are explaining well but I just can't force my brain to comprehend :s-smilie: AS chemistry is soooo hard


Lol I know what u mean I'm now an A2 student (A2 is even harder :/ but more interesting in my opinion)

Well y it doesn't go multiple s sub shells in one shell idk I think it has something to do with the energy levels(although hopefully someone with more chemistry knowledge can explain this) .





Posted from TSR Mobile
Original post by JN17
There is only one S orbital per shell, hence only one '3s...' available to fill electrons. Electrons always fill from the lowest energy level subshells first (ignoring the 3d&4s exception).
For titanium like you mentioned, it is in the d block, 3rd period and 2 along, so its outermost subshell is 3d2. Working backwards (filling everything before 3d2), we get 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d2. I'd imagine the reason 4s2 is there can be confusing so I'd advise you to see the picture here http://www.mikeblaber.org/oldwine/chm1045/notes/Struct/EPeriod/Struct09.htm
(idk how to attach images). If you were to label titanium on that image (2nd in from the left of 3d), you'd fill every subshell up to that point working from top left to bottom right of the table.


Alright cool! I think I can do the outmost subshell part! Ummm, I think I'm kinda confused....why/how do you go 2 along? And I thought titanium is in row/period 4? and it's in transition metal part? Can we do Potassium as an example please
Reply 15
Original post by Perfection Ace
Alright cool! I think I can do the outmost subshell part! Ummm, I think I'm kinda confused....why/how do you go 2 along? And I thought titanium is in row/period 4? and it's in transition metal part? Can we do Potassium as an example please

Well titanium is in the fourth row on the periodic table, however as you see in the picture the 3d part lies between 4s and 4p (it's a bit weird), but if you look at the periodic table and that image alongside eachother titanium represents the 2nd one into the 3d section. I believe for AS you don't have to know why this happens but you do have to know how to write electron configurations for at least the first 36 elements (for my board at least).
Potassium is the first element in the 4s part of the table, hence it's outermost subshell is 4s1. Filling everything before this you get 1s2, 2s2, 2p6, 3s2, 3p6, 4s1.

-As for the 3d/4s thing, the 3d subshell has a higher energy level than the 4s subshell but only slightly. The subshells overlap however electrons will fill the 4s subshell before the 3d subshell

https://en.wikibooks.org/wiki/High_School_Chemistry/Electron_Configurations
This has a pretty good representation of how the subshells fill with increasing energy levels (also just pretty good for explanations of orbitals/subshells in general)
Original post by JN17
Well titanium is in the fourth row on the periodic table, however as you see in the picture the 3d part lies between 4s and 4p (it's a bit weird), but if you look at the periodic table and that image alongside eachother titanium represents the 2nd one into the 3d section. I believe for AS you don't have to know why this happens but you do have to know how to write electron configurations for at least the first 36 elements (for my board at least).
Potassium is the first element in the 4s part of the table, hence it's outermost subshell is 4s1. Filling everything before this you get 1s2, 2s2, 2p6, 3s2, 3p6, 4s1.

-As for the 3d/4s thing, the 3d subshell has a higher energy level than the 4s subshell but only slightly. The subshells overlap however electrons will fill the 4s subshell before the 3d subshell

https://en.wikibooks.org/wiki/High_School_Chemistry/Electron_Configurations
This has a pretty good representation of how the subshells fill with increasing energy levels (also just pretty good for explanations of orbitals/subshells in general)


Thanks, i'll revise the 3d/4s thing tomorrow! Also, how many marks would you say it would give for working out EC for potassium?
Reply 17
Original post by Perfection Ace
Thanks, i'll revise the 3d/4s thing tomorrow! Also, how many marks would you say it would give for working out EC for potassium?

Most likely only 1-2 as it would be just a part to a much longer question or just a multiple choice question. Once you do some practice they are very easy, I'd advise you to try do the configurations of a few random elements or just say what the outermost one is and make sure you know the order that the electrons fill the subshells in.
Original post by JN17
Most likely only 1-2 as it would be just a part to a much longer question or just a multiple choice question. Once you do some practice they are very easy, I'd advise you to try do the configurations of a few random elements or just say what the outermost one is and make sure you know the order that the electrons fill the subshells in.


Okay, cool! :smile: Are you doing AS or A2?
Reply 19
Original post by Perfection Ace
Okay, cool! :smile: Are you doing AS or A2?


Just finished AS, started A2 last week :smile: ( for maths, fm, physics&chemistry), pretty worried about how revising for exams is going to be like this year, having to know 2 years of content for 2 subjects :/, and yourself?

Quick Reply

Latest