The Periodic Table

CowperKettle

03:12

Which is better to write: "S-adenosylhomocysteine" or "S-Adenosyl-L-homocysteine"?

Or maybe it does not matter?

My Russian text uses the un-hyphenated form, so I tend to translated it using the unhyphenated English form

ringo

04:07

The IUPAC name is S-(5'-Deoxyadenos-5'-yl)-L-homocysteine

@CowperKettle If that helps your decision

CowperKettle

@ringo Thanks! I'll go with my first option then

> We placed 6.057 g of tris(hydroxymethyl)aminomethane into a 300 ml beaker, added 250 ml of water and mixed to complete dissolution. (<< is this the standard phrase, or is it some other phrase?)

The Ludwig engine proposes "stirred until complete dissolution", but I'm not sure whether that thing was actually stirred (with an external object being put into it) or just mixed.

orthocresol

04:30

Gosh, what, we are also having mod elections?!?!

@Mithoron The last thing I voted in, we lost 48-52 ):

@CowperKettle If I was carrying this out, I would use a magnetic stirrer, but of course I can't say anything as to how they did it.

CowperKettle

@orthocresol Ah, so "stirred" is okay. I shall use "stirred" more often

orthocresol

And I would actually probably not bother writing that it's stirred until it fully dissolved.

CowperKettle

> [Here is nothing missing, but a cat urinated on this during a certain night. Cursed be the pesty cat that urinated over this book during the night in Deventer and because of it many others [other cats] too. And beware well not to leave open books at night where cats can come.]
Cologne, Historisches Archiv, G.B. quarto, 249, fol. 68r

@orthocresol How would you write it?

orthocresol

Because it's implied, I mean you "dissolved" it in 250 ml water :>

CowperKettle

ah! Probably in Russian there is this phrase that is not used in English.

orthocresol

04:43

"10 g of X was added to a 300 ml beaker and dissolved in 200 ml water"

CowperKettle

nods

Probably the same as with "termostat" (Russian for any kind of lab heater)

> We incubated the resulting solution in a termostat at 37 °С for 18 h. >> "We incubated the resulting solution at 37 °С for 18 h."

No meaning is lost by omitting it.

And it is seemingly okay to drop the preposition of

> [...] dissolved in 200 ml water

orthocresol

04:59

Hmm, there is no harm in including it either.

CowperKettle

Is it okay to write "Following the incubation, we diluted the solution in a 15 ml tube 100 times with cooled 10 mM sodium acetate buffer (pH 5.2)."? (the solution was diluted to 1% of its initial concentration)

orthocresol

Oh, sorry, there should be an of there.

CowperKettle

ah!

orthocresol

Regarding the dilution, I think "diluted by a factor of 100" is clearer?

Maybe?

Question marks because I'm not 100% sure

CowperKettle

Ludwig offers examples of "100 times", but these could be by non-natives

orthocresol

05:01

Because diluting it 100 times sounds like... Well... diluting it 100 times :p that's some homeopathy level stuff.

CowperKettle

(0:

Google books finds 59 results for 'diluted by a factor of'

orthocresol

I'm not sure. There are other constructions that I have seen, such as "5 g of benzaldehyde was dissolved in 10 ml of 1,2-dichloroethane and diluted to 100 ml with chloroform."

or equivalently (in this hypothetical scenario), "... and diluted with 90 ml of chloroform."

I've never seen "diluted X times", but I would hesitate to pass judgment on it as being wrong.

CowperKettle

05:18

diluted 1:100? diluted 100 folds?

anyway, the reader will understand, even if that will be awkward

orthocresol

"diluted 100-fold"

CowperKettle

nods

orthocresol

flag as spam please: chemistry.stackexchange.com/a/59791/16683

CowperKettle

done

ringo

05:36

done and done

orthocresol

gosh, how did it get -7 in 15 minutes?

our site is GROWING

ringo

Another: chemistry.stackexchange.com/a/59793/15410

The spam is growing proportionally I guess

-6 in 3 minutes! Now that's what I'm talking about!

CowperKettle

Le Spamelier's Principle

4

CowperKettle

05:55

> MS detection conditions:
Parameters of the ionization source:
Spray gas (N2) pressure:
40 units;
Auxiliary gas (N2) pressure:
20 units;

Do they call it "spray gas" and "auxiliary gas" in Mass Spectrometry?

I merely copied the Russian terms.

And the original says "Spray gas speed" but I changed it to "pressure" after some googling.

Oh, it's ion source

Not "ionization source"

Ion source

An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines. == Electron ionization == Electron ionization is widely used in mass spectrometry, particularly for organic molecules. The gas phase reaction producing electron ionization is M + e − ⟶ ...

Maybe it is sheath gas

Must be ESI (electrospray ionization)

ringo

06:46

22 items up for review

Crazy

Aaron Abraham

@Loong and @getafix, I know I'm relying on you guys a lot for electrochemistry queries.....well you guys DO give great answers (please take that as a compliment).....but yet another one if you won't mind: chemistry.stackexchange.com/questions/59798/…

orthocresol

07:16

@ringo I think Martin has done something, it is now down to 6 ;D

ringo

Haha very good

As low as it ever seems to get

orthocresol

08:11

@AaronAbraham please don't add tags that don't exist, like nucleophilic-substitution

If you believe that having such a tag is beneficial, start a discussion on Chemistry Meta.

Aaron Abraham

08:46

@orthocresol Wait, I thought I could create tags...

So......only tags that already exist huh? Roger that.....

orthocresol

8

A: What do I need to know about tagging?

How to find out if a tag is good to have/make I present to you, the MAR Tag Test™ (abbreviated as MATT), a short test with three possible responses to each question, designed as a crude way of diagnosing the health of a (imaginary) tag. Imagine X, a tag$\,\ldots$ 1: Ignore spam. Some people ...

By virtue of having 300 reputation, you have the ability to create new tags, but the way we do it is new tags only get added by consensus.

(Side note: I never understood, why is it MATT and not MARTT...)

Aaron Abraham

So if my tag scores an excess of 16 points on the MATT scale, should just directly create it or still discuss it on meta first?

orthocresol

Meta. That would be grounds for constructive discussion.

Aaron Abraham

Point taken......

....and thank you.

orthocresol

Everything's welcome on meta, we don't quite get enough meta discussion.

Aaron Abraham

08:55

Is that why everything's welcome? :P

ringo

4 am and I just finished my lab report

Don't know whether to be happy or depressed

orthocresol

Well, except for rants about how the place is rubbish. If you want to tell us how it's bad, that's fine, just not in this way..

ringo

Oh that post... lol

orthocresol

@ringo Oh dear..

Go and catch some sleep.. haha... well done.

ringo

Every week I say I'm not gonna wait till the night before and every week I find myself in the same situation

Probably wouldn't be so bad if I stayed off chem.se lol

it's just so much more fun than optics

orthocresol

08:59

B-b-but you're doing chemistry, so you're doing real work

ringo

I wish I was doing chemistry

orthocresol

on this website, you are :p

ringo

Oh, right

I'm tired lol

orthocresol

That sounded uncannily like yoda.

ringo

Tired I am

orthocresol

09:00

My last message, I mean :D

ringo

Oh haha

Jeez I'm too tired

making a fool of myself left and right

orthocresol

Good night!

ringo

Good night!

Wildcat

Is is night already?! :O :P

Meow!

Aaron Abraham

@ringo.....but optics IS fun.....

By the way @orthocresol are you a physical chemistry guy by any chance? (something about your username tells me you're the Org.Chem type.....but I can't put a finger on it....)

orthocresol

09:14

Technically, I'm an every-chem seal.

Aaron Abraham

Oh wait....still under-grad right?

orthocresol

Mmhmm.

Aaron Abraham

(That's better than my situation....high-school.....bleh)

this certainly was very......amusing....

-12

Q: Can we please be friendlier at least in the beginning?

I am a PhD in Chemistry, who graduated from a top 20 university in the US, failed to find a job in the field and moved to CS. Chemistry field doesn't have much of job security, so that was a good choice. I ask beginner's questions on StackExchange, but I want to pay back by answering questions on...

discussion

@orthocresol I believe o-cresol's toxic to seals.....

user228700

Hello everyone :-) I'm struggling to understand the concepts of ionic equilibrium and am even a little annoyed by the whole chapter. (Actually, "little" is an understatement) Can anybody be so kind as to tell me why we study ionic equilibrium in the first place? Does anybody have first hand experience?

Wildcat

09:40

@KaumudiHarikumar We study it to be able to calculate concentrations of substances in solutions.

This in turn allows us to predict and control what will happen in a particular solution.

user228700

@Wildcat Like what?

Wildcat

@KaumudiHarikumar like what will happen if you mix solution A with solution B.

or what do you need to add to solution to change it as required

user228700

@Wildcat What kind of solutions are we talking about?

Wildcat

Myriads of chemical reactions in lab, nature, industry occur in solutions.

@KaumudiHarikumar any solution, but usually it means any aqueous solution

user228700

@Wildcat Hm, OK. Thanks :-)

CowperKettle

09:45

I recall that I did not manage to understand the ionic product for water and other related stuff

It was explained too obstrusely in my textbooks and online

I had a headache each time I tried to understand those equations with square brackets

Wildcat

Hmmm... They are relatively simple.

@CowperKettle it is just the equilibrium constant for the reaction in which water undergoes an acid-base reaction with itself.

@KaumudiHarikumar btw, is there any chapter on chemical equilibrium in a book you're reading prior to a chapter on ionic equilibrium?

user228700

@Wildcat Yep. Why do u ask?

Wildcat

@KaumudiHarikumar cause (as I already mentioned) ionic equilibrium is just a particular kind of chemical equilibrium. If you understand the general concept of the later, the former is just a trivial example.

With myriads practical applications, though. :)

user228700

@Wildcat Hm, I see. OK, thank you :-)

Jan

Waitwot? We're having an election? O__O

user116211

09:54

@Jan No?

orthocresol

@Jan I didn't expect it either, current mods have been doing great.

user116211

Or really?

user116211

@jan, where did you get the news?

user116211

@orthocresol That may not be the reason.... wait:

user116211

> When all four of us are available, we have no problem with the current workload. But if a couple mods are traveling or without internet access, it becomes hard to keep up, and that happens often enough that we'd like to expand the moderation team to avoid being shorthanded.

user116211

09:57

This was said by David Z; one of the existing mods at Phys.SE.

Jan

@MAFIA36790 Chemistry Meta

user116211

The moderation work is going well at Phys.SE but in case hands fall short...

user116211

@Jan NO WAY!!

orthocresol

@MAFIA36790 oh well, why are you so surprised then haha

user116211

It's a bit early, i would say @jan.

user116211

09:59

@orthocresol ^

user116211

There are many good possible candidates in Chem.SE.

Jan

@MAFIA36790 Can't tell if you're joking or honest atm o.o'

user116211

@jan @ortho, would you like to run for the election?

orthocresol

Nah.

Jan

Nope. Can't afford losing even more time.

user116211

10:02

You, people ;(

user116211

Anyways, @Rubisco, would you like to run in the election?

user116211

Respond later when you come.

orthocresol

I spend a lot of time on chem.se, but I am more interested in the chem, less so in the se part.

user116211

@orthocresol okay.

Jan

I probably could see myself doing it, but I would see myself wasting way too much of my valuable time (which I am already pretty much wasting right now).

user34388

10:10

Is it that when i construct LCAO, i can make the p orbitals point in any direction as long as they are orthogonal? Can i make p orbitals of different atoms point at different direction as well?

Wildcat

@user34388 no, you choose the coordinate system once and forall for the whole molecule in the beginning, and not for each and every atom.

Once coordinate system is chosen, p_x orbitals of all atoms will point in exact same direction.

Whatever the direction of x axis is.

@Jan So, wait. Do you seriously consider writing about German chemistry related mnemonics a waste of time? :O

user34388

@Wildcat I see, thanks

Jan

@Wildcat Huh?

Wildcat

@Jan anodische Oxidation ist das A und O. :D

user34388

@Wildcat we do it as "anox redcat"

user116211

10:21

@wildcat, what about you? Would you like to run for the election?

Jan

Why waste of time?

Wildcat

@MAFIA36790 nope.

@Jan cause you said that! "I am already pretty much wasting right now"

user116211

ohh. So no one wants to be a mod ;/

Wildcat

Or, did you said it about chatting with us?! :O

orthocresol

@MAFIA36790 rubisco said he would run.. so we have one, at least.

Jan

10:24

@Wildcat Oooooh! xDDD

user116211

@orthocresol Ah! He would be a good mod.

Jan

That was a reference to me being on chem.SE too much altogether ;)

Wildcat

@user34388 IIRC, we just memorised that both anode and oxidation start with vowels, while cathode and reduction with consonants.

Oh, wait we have another elecrochem mnemonic! In Russian words "anode" and "plus" both contain 4 letters, while "cathode" and "minus" both contain 5 letters. :D

CowperKettle

(0:

user34388

@Wildcat that is nice

if i were to change my name, would "DHMO" be a good name?

CowperKettle

10:35

I wonder what the meaning of "Ширина пика отфильтрованной массы: Нижний предел 0.5, верхний предел 2.0" could mean in a description of Mass Spectrometry parameters.

Literally it is "Peak width of the filtered mass: Lower limit 0.5, upper limit 2.0"

But what it means is beyond me.

user34388

is there acid polybasic but monoprotic?

CowperKettle

> Polyprotic acids, also known as polybasic acids.. (WIKIPEDIA)

So there must be no such acids.

user34388

ok thanks

CowperKettle

np

yw

user34388

what is the relationship between H2CO3 and CO3^2- called?

Wildcat

10:50

@user34388 acid (H2CO3) - conjugate base (CO3^2-)?

@CowperKettle I did some massspec in the past, but also don't understand the phrase. :D

Conjugate acid

A conjugate acid, within the Brønsted–Lowry acid–base theory, is a species formed by the reception of a proton (H+) by a base—in other words, it is a base with a hydrogen ion added to it. On the other hand, a conjugate base is merely what is left after an acid has donated a proton in a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid. In summary, this can be represented as the following chemical reaction: Acid + Base ⇌ Conjugate Base + Conjugate Acid Johannes Nicolaus Brønsted and Martin Lowry introduced the Brønsted–Lowry theory, which proposed...

user34388

@Wildcat i meant it is only applicable to the transfer of one proton

Wildcat

@user34388 no, to my knowledge.

CowperKettle

@Wildcat Another column in the table is titled "Ширина пика массы zoom-скана" (Peak width of the zoom scan mass), and upper limit = 5.0, lower limit = 5.0

Wildcat

The definitions are with respect to a particular chemical reaction.

So, if you have, say, H2CO3 + 2NaOH -> Na2CO3 + 2H2O

then acid (H2CO3) - conjugate base (CO3^2-) is valid

relationship

@CowperKettle My guess is that it is all about accuracy of the device. In the zoom-scan mode the accuracy is worse than in the filtered mode.

Whatever these mode are. :D

And accuracy is given through the pick widths.

CowperKettle

Yes, I'm reading now about zoom mode. It is "slower" (but how can an ion fly "slower"?)

I need a good textbook PDF on mass spectrography, from beginner's level and up

Wildcat

11:06

Zoom mode probably refers to zooming in a particular part of a mass spectrum.

You are zooming in just a small region of masses but spend more time to get a better accuracy. That's why it take more time (is slower).

Ions still fly with the same speed, we just spend more time for counting them to increase the accuracy.

But it is just a guess...

For a book, I can recommend de Hoffmann, Stroobant - Mass Spectrometry.

CowperKettle

@Wildcat Thank you, I'll look it up

Wildcat

I even failed my MS exam once until discovered this book. :D

CowperKettle

(0:

Wildcat

Or Downard - Mass spectrometry. A foundation course as a rather short intro.

CowperKettle

I found Hoffman

Rahul2001

11:23

Hi

I'm studying for my exam tomorrow and have a very minor doubt

Am I correct in thinking that respiration is a decomposition reaction whereas photosynthesis is a combination reaction?

CowperKettle

I wonder what Activation Q is in Mass Spectrometry

orthocresol

Sorry, I would help if I knew more about MS..

CowperKettle

No problem! I'll find that out.

source

Jan

@Rahul2001 I would say those two are far too strong generalisations.

Rahul2001

@Jan Oh. I see. My textbook says that photosynthesis is a combination reaction, and while it says that respiration is basically the opposite, it doesn't say what kind of reaction it is

Jan

11:37

@Rahul2001 They both kinda make sense, but in my opinion the terms combination and decomposition are too generalised in themselves to properly apply them.

Rahul2001

@Jan Ah, okay, thanks...

orthocresol

I like calling them anabolic and catabolic :)

Jan

@orthocresol That's a great idea @rahul, except I can never remember which is which xD

orthocresol

@Jan catabolic $\approx$ cutabolic = cutting things down..

That's the worst mnemonic I've ever made up.

:D

Jan

The worst (and best) mnemonic I ever heard was:

Loong

11:43

@Rahul2001 Respiration and photosynthesis are not just simple chemical reactions; they are complex processes that involve various chemical reactions. Your definition of decomposition and combination may be comprehensible from the point of view of carbon in carbon dioxide and sugar.

Jan

> Boah! A Suzuki!

(Boah! being an exclamation of surprise and awe, similar to wow in English and pronounced just like Bor, the German word for boron. Suzuki is, of course, both a name reaction and a motorbike.)

orthocresol

@Jan What does that even mean?!

Gosh..

That's pretty witty actually

Jan

@orthocresol 'Tis great, innit? ^^

orthocresol

;)

Jan

So the anabolica that Tour-de-France cyclists use, are building up their muscle power. I think I can finally make some sense out of those words =D

Loong

11:46

@orthocresol I guess, I dont want to hear how you remember stalagtite/stalagmite. ;-)

Jan

> Stalaktiten hängen runter wie die Titten.

*runs before @ina realises I spoke German*

orthocresol

@Loong Ah, in English, this is widely taught.

It's stalactite - and that's because they come from the ceiling.

Jan

The German mnemonic is better imho O:)

Loong

@Jan Of course, I use the French way: monter, tomber

Wildcat

@Jan certainly! :D

Jan

11:51

@Loong ;p

Loong

@Jan That also works in English.

orthocresol

@Loong I am pure and innocent... don't..

Jan

@orthocresol There's no way I wouldn't star that ;p

orthocresol

11

Q: How do you remember the difference between a "stalactite" and a "stalagmite"?

Is there a good mnemonic for remembering the difference between "stalactite" (hangs down) and "stalagmite" (points up)?

confusables

Jan

7

A: How do you remember the difference between a "stalactite" and a "stalagmite"?

Let me give you another mnemonic, closer to the heart of some: Stalactite = tit Stalagmite = you already remembered the tit one This is how we remember it in Dutch, in which language it actually rhymes: stalactiet - tiet.

orthocresol

11:55

27

A: How do you remember the difference between a "stalactite" and a "stalagmite"?

Here is one from my secondary school geography teacher that I will never forget: stalactite --- ceiling stalagmite --- ground Stalactites hang from the ceiling; stalagmites rise from the ground. As long as you remember what c and g mean in those words, you will never confuse them!

Jan

@orthocresol booooring! ;p

orthocresol

Hahaha :D

Wildcat

80 points by citing a couple of IUPAC definitions? Not a bad day! :D

Jan

@Wildcat 80?!? I’m close to rep cap xp

Wildcat

@Jan yeah, but your answer is more involved. Plus the mnemonic!

getafix

12:11

@Wildcat 80 :O

Wildcat

@getafix 8 upvotes, yes.

getafix

wow!

I spent like an hour answering one question today, and got just one hahaha lol

Wildcat

I know that feel.

getafix

unfortunately, that's the only contribution I made here today

Jan

Was it the upvote I gave @getafix? ;D

Wildcat

12:15

1

A: Why is a buffer solution best when pH = pKa i.e. when A-/HA=1

Preliminaries There are many ways in which you can go about defining a "Buffer Capacity". A good intuitive way to start would be to say, it is tha maximum amount of acid (or base) the solution can tolerate before it starts showing a significant change in pH. While this is not bad, it obviously b...

getafix

@Jan

Perhaps..I can't tell

Wildcat

Oh boy, so much effort for just a single upvote!

getafix

or atleast I don't know how to

Jan

Nope, that wasn't me, Didn't open that question.

getafix

@Wildcat yeah haha

orthocresol

12:16

I actually didn't read it.

Long mathsy answers tend not to get a lot of rep.

getafix

@orthocresol i've noticed, but i do it for the exercise mostly

Wildcat

@orthocresol unless they are qchem or td related.

orthocresol

Oh well, I am preparing a long mathsy qchem q&a :)

Wildcat

@getafix exercise in LaTeX? :)

@orthocresol me too.

orthocresol

@getafix mmhmm, I actually just like seeing the equations come out nicely.

Wildcat

12:17

@orthocresol Hope we aren't doing it for the same question. :D

orthocresol

@Wildcat i'm doing (hopefully) a canonical answer proving heisenberg UP..

getafix

True true

Hey guys..

what is a good way to deal with a prof./dept head who is asking me to do something, which I am uncomfortable doing (basically I am philosophically/morally opposed to what he is asking of me)?

Wildcat

@orthocresol Where by "nicely" you mean "without derivation"? And this man dislikes Atkins' prose? :D

orthocresol

@Wildcat Atkins' proof of HUP consists of:

Wildcat

@orthocresol I remember we had a couple of questions on that matter. I think I even answered one...

Jan

12:19

@getafix I think I would ask over at Academia o.o' Tbh I have no clue and I am definitely not prepared should I end up in that situation.

orthocresol

"Now, we know that $[x,p] = i\hbar$. It is therefore immediately obvious that $\sigma_x \sigma_p \geq \hbar/2$".

getafix

@Jan yeah but I don't want anyone finding out about it, and I am not willing to give away too many details at this stage..

Wildcat

@orthocresol yeah, not immediately, of course :D

orthocresol

@Wildcat Yeah, you have a couple of answers on the matter, but neither do the full proof of the Robertson relation. So I figured I'll just do an exercise in latex :D

getafix

at one point he wished to read an email meant for another person (before I send it)..

and I was like no..

orthocresol

12:21

@getafix I believe academia should have several posts on it.

getafix

trawling through right now..

Wildcat

@orthocresol IIRC, Atkins first proves the uncertainty relation in its general form, so that is fine than just to say what he says.

orthocresol

I can't remember offhand but I think you are right. I think that is the sensible way to do it , anyway.

Wildcat

Aha! This was the question on HUP I answered back in the days.

9

A: Significance of 4π in the uncertainty principle

The quantity on the right side of the expression for the product of uncertainties basically depends on the mathematical definition of "uncertainty" used. Without rigid definition of this quantity one ofthen just say that the product of uncertainties in position and momentum is of the order of Pla...

7

A: Is the uncertainty principle axiomatic or derived?

You may be confusing two things here. The uncertainty principle, which states that for any two observables $A$ and $B$ $$ \sigma_{A}\sigma_{B} \geq \frac{1}{2}\left|\langle[\hat{A},\hat{B}]\rangle \right| \, , $$ can be derived (see, for example, Proof of the Schrödinger uncertainty relation ...

Another one was on Physics.SE, in fact.

user116211

@Wildcat Yeh, a dedicated post on QFT.

getafix

12:24

Hahah @Wildcat are you a physicist or a chemist by trade?

user116211

@getafix ;))

Wildcat

@getafix a physical chemist.

getafix

Oh cool

Aaron Abraham

Could someone suggest a decent tag for this?

0

Q: What is the composition of the oil-like fluid that seeps out of dry-cells over time?

An experience a lot of us might've had; a dry cell (not completely depleted) when left in an electrical device for long periods of time, has this viscous fluid coming out that usually corrodes the terminals of the battery. I almost always find this fluid, present as a sorta thin film over the te...

electrochemistry

orthocresol

@AaronAbraham nothing specific is good here. I would suggest everyday-chemistry, reaction

Aaron Abraham

12:35

Roger that....

user34388

After a survey in which all respondents agreed... I'm officially going to change my name to DHMO.

Can a mod refresh here?

@Loong

Loong

@DHMO done

DHMO

@Loong Thanks

orthocresol

@Loong Black magic..

Jan

Right, rep capped. I could just leave, now ^^

Wildcat

12:49

No, you could not! :D

DHMO

13:10

So, I tried to draw the MO of O4 (tetrahdron)... and I got only 4 energy levels... with nine molecular orbitals occupying the highest energy level

Did I do anything wrong?

Wildcat

13:21

@orthocresol I'm done with my answer! :)

0

A: Why are excited Slater determinants used to describe electron correlation?

As I mentioned in comments, professor Jack Simons offers a relatively simple physical interpretation of the idea of mixing in excited detrminant for treating dynamical correlation in his book "Quantum Mechanics in Chemistry" (Chapter 8) freely available here, as well as in this video which is als...

DHMO

@getafix Could you help me?

getafix

@DHMO Maybe..what do you need help with?

DHMO

> So, I tried to draw the MO of O4 (tetrahdron)... and I got only 4 energy levels... with **nine** molecular orbitals occupying the highest energy level
Did I do anything wrong?

getafix

and wait..what was your old nick? lol

I get so confused..

DHMO

@getafix user34388

getafix

13:23

ahhh lol

I don't think I can, not with that question..

DHMO

Alright

I didn't bring back home my drawing

getafix

ah that's unfortunate..

sorry though, presently trawling for questions that I can answer quick and get some rep.. haha

DHMO

@getafix basically I arranged the 2s orbitals as such

and I also arranged the 4 2px orbitals as such

same for the 2py and the 2pz

Using this coordinate system:

@getafix

getafix

@DHMO I might be betraying some ignorance on part, but I really don't follow lol sorry

let me try and understand your problem first..haha

So you are imagining O4 like a CH4 tetrahedron?

DHMO

@getafix without the C

getafix

13:32

hmm

DHMO

The 4 orbitals on the right

getafix

maybe try a P4 tetrahedron?

In fact, I remember reading something about a theoretical model for tetraoxygen..

can't remember what it was..

DHMO

@getafix nice suggestion... but I can't find it online

getafix

Tetraoxygen

The tetraoxygen molecule (O4), also called oxozone, was first predicted in 1924 by Gilbert N. Lewis, who proposed it as an explanation for the failure of liquid oxygen to obey Curie's law. Today it seems Lewis was off, but not by much: computer simulations indicate that although there are no stable O4 molecules in liquid oxygen, O2 molecules do tend to associate in pairs with antiparallel spins, forming transient O4 units. In 1999, researchers thought that solid oxygen existed in its ε-phase (at pressures above 10 GPa) as O4. However, in 2006, it was shown by X-ray crystallography that this stable...

It wasn't that, I read about it in a different context..

maybe one of the references can be helpful though?

DHMO

@getafix It isn't tetrahedral... my interest is not on the O4 molecule

I'm just using the O4 tetrahedral MO to build SO4^2-

getafix

13:35

Oh I see.

Jan

@DHMO Oh group orbitals. I failed when I was supposed to realise to what they transform to after C_3 rotation.

DHMO

@Jan You can visualize using a cube

Also I just built my 16 MOs based on the 4 MOs on the right hand side:

Basically, I had my 4 2s orbitals follow the 4 MOs on the right hand side

and then the 4 2px orbitals

etc

Jan

@DHMO Yeah, but then you need to transform the p-orbitals, too.

DHMO

So they are symmetrical under C3... just that an MO transforms to another MO under C3

so they are grouped in groups of three

which when combined would be symmetrical under C3

Jan

That is, if you want to describe them by group theory.

DHMO

13:47

(and the one remaining orbital is the bonding 2s orbitals)

@Jan I actually do not understand the formal way of doing it

I red through this text: chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/…

@Jan I would absolutely love it if you could teach me how to formally construct LCAOs

Is SALC the only way?

Jan

Alas, I cannot.

DHMO

Alright

but could you tell me what transform means?

4 mins ago, by Jan

@DHMO Yeah, but then you need to transform the p-orbitals, too.

pentavalentcarbon

@DHMO That's basically how you do it.

Jan

Apply an element of symmetry to them and see what they end up as.

DHMO

@pentavalentcarbon Yes but I do not understand it...

@Jan so px ends up as py and then as pz?

Jan

13:55

As I said, I am not confident in explaining it ^^'

DHMO

@pentavalentcarbon Would you be able to solve my problem?

33 mins ago, by DHMO

> So, I tried to draw the MO of O4 (tetrahdron)... and I got only 4 energy levels... with **nine** molecular orbitals occupying the highest energy level
Did I do anything wrong?

Jan

Anyway, with that I am going to close SE for today o/

etherealflux

Bleep bloop

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