electron configuration (1 Viewer)

[David Spade]

lol ok i know

i should know this, and i was going fine with it until i hit a wall and now im stuck

ok so the # electrons in the outer shells is worked out by 2n(2) right?

so 1st shell holds 2
2nd shell holds 8
etc etc

and that the number of electrons in the last shell should tell you which group the atom is in on the periodic table? amirite? because i'm confused. does this only rule not include the transition metals? coz one of the questions was like;

Cs and the electron configuration was 2:8:18:26:1 and i was like wtf why didnt the 1 just go in with the 26 to make 27 coz it can hold 32??

anyway. im sure one of you fantastic chem nuts will have an answer for me, to which i will reply with the dummkopf sound

 

[Trebla]

I think the real explanation behind that is under the quantum model of the atom, which you don't cover in high school lol...

A more high school type explanation is to note that Cs has a valency of +1, therefore one electron must appear in the outermost shell. Having 27 electrons in the outermost shell does not give it that valency, so one electron must reside in the next highest shell.

 

[David Spade]

yeah ok cool story hansel. i'm at uni, and i figured if anybody was gunna know it'd be the hsc chem freaks

the explanation i require should be covered at an hsc level, and the study guide ive got doesn't tell me. i know that there is a reason for why but it doesnt tell me and im frustrated

like it literally goes from saying "blh blah electron configuration" and then it goes on to say 3 lines about valence shells and atoms being arranged vertically according to the # electrons in outermost shell

and then thats it. then i have a question that lists things like caesium and it doesnt tell me why we deliberately dont fill the shells

 

[David Spade]

I think the real explanation behind that is under the quantum model of the atom, which you don't cover in high school lol...

A more high school type explanation is to note that Cs has a valency of +1, therefore one electron must appear in the outermost shell. Having 27 electrons in the outermost shell does not give it that valency, so one electron must reside in the next highest shell.

yay see ok so it's about valency

i was confused because the guide doesnt explain valency, it just says "lol the outermost shell is the valence" and then everything i look at at uni level says "fuck off, valence is a misnomer"

 

[David Spade]

so, everything else from groups 1-8 is correct and the outer shell should add up to the group

except for transition metals which are 1 or 2?

 

[David Spade]

ill post the study guide so you guys know what the gap is i am referring to

the gap of knowledge

 

[David Spade]

never mind, im just gunna neck myself instead

have to go look up chem stuff from last year to help me with a refresher course

defeats the purpose of doing a refresher course

 

[appletooth]

Correct me if I'm wrong, but I think this has something to do with Schrodinger's model? (That was covered in year 11, not HSC chemistry.)

Bohr's model stated that there was a maximum number of electrons which can occupy any given electron shell/energy level - which is where your 2n^2 comes into it. 2n^2 only gives you the max number of electrons in the outer shell.

But Schrodinger's model went one step further and said that electron shells in an atom are further subdivided into subshells (called "s", "p", "d", "f", "g").

The S subshell holds a max of 2 electrons (1 pair).
The P subshell holds a max of 6 electrons (3 pairs).
The D subshell holds a max of 10 electrons (5 pairs)
The F subshell holds a max of 14 electrons (7 pairs).
... etc etc.

But subshells don't fill with electrons in exact consecutive order due to energy considerations (a really vague reason why - but I don't know, it's as far as we got in year 11. Google it if you must know more?). So if we go by Schrodinger's model, that should sort of answer your question, I think...

Edited to add ---

http://www.green-planet-solar-energy.com/electron-details.html

^ More on the filling of subshells, if needed. Use that grid thing to work out how many electrons are in each shell.

 

[katie tully]

yeah thats correct, but essentially i think my study guide was wrong

i did bohr and schroe last year, but those topics were way after the introduction of the periodic table

this refresher course doesn't mention that stuff for another few topics, so i was wondering whether there was something really simple i was missing, or whether theyd just accidentally omitted a heap of info


thanks though

edit: see this is the study guide copied and pasted. it's missing a heap of info, i think.

Electronic configuration
The further away the shells are from the nucleus the more space the electrons
have and a larger number of electrons is allowed in each level.
Maximum number of electrons per shell = 2 × (shell No.)2

The first shell of Br can take 2 electrons. Another 8 electrons can go in the
second shell. But that has only taken care of 10 electrons altogether. There are
still 25 electrons to arrange around the nucleus. 18 of these 25 can go into the
third shell leaving 7 electrons to go in the fourth shell.

The atoms are arranged in VERTICAL groups in the Periodic Table. These
GROUPS of atoms all have the same number of electrons in their outermost shell.
The outermost shell of an atom is known as the valence shell.

 

[cutemouse]

I think the real explanation behind that is under the quantum model of the atom, which you don't cover in high school lol...

Isn't that covered in HSC Physics? lol

 

[Trebla]

Isn't that covered in HSC Physics? lol

HSC Physics doesn't look at the electron orbital theory and Schrodinger's wave equations particularly with regards to configurations of electron orbitals (i.e. the s, p, d, f etc orbital configurations).
In uni Chemistry, the Bohr model of the atom becomes completetly rejected and you have to see things in the light of the quantum model. In other words a lot of the explanations you learn in high school Chemistry are no longer widely accepted or they do not give the complete picture.

 

[Pwnage101]

Mods, move this to uni science forum?