The Periodic Table - 2016-09-16 (page 1 of 2)

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12:02 AM

@MartianCactus pure acids usually don't react as an acid

5 hours later…

4:52 AM

@orthocresol True, but OP’s doing his best to ask it in a chemical way … — Jan 10 hours ago

he's also doing his best to be an insufferable smart alec, so I'm not going to bother with that question any more, or anything else coming from this guy.

@user34388 They certainly do.

that said, I have no idea how metal oxides behave with conc. H2SO4, so I have no answer to the original question

conc. HCl has plenty of water inside (pure HCl being a gas), so my first thought would be that it would react pretty much in the same way as dilute HCl

1 hour later…

6:23 AM

@orthocresol well, I just went against what I said

@orthocresol conc HCl is not pure HCl

@user34388 oh, fair enough

so they certainly dont

HCl gas still behaves as an acid though

oh yes it does

what?

6:28 AM

what what? This is literally the "most famous example" of Bronsted-Lowry theory.

NH3(g) + HCl(g) -> NH4Cl(s).

I see.

never touched that theory

time to touch it then, cause it's much more useful than plain old Arrhenius

is there any bonds broken in that reaction?

you could say H-Cl is broken because NH4Cl is ionic

I see

@orthocresol do you think it would have a normal energy graph?

6:32 AM

what does normal mean?

one crest

going up then back down again?

yes

i don't know

i can see a simple two-step energy transfer

except for forming the ionic crystal

i meant electron transfer

6:33 AM

there's no electron transfer

only proton

right

why does Cl• want to become Cl- ?

it isn't like single electron has more energy than a pair

why is there Cl. in the first place?

aha

from Cl2?

huh?

where did Cl2 even come from

from two Cl•, lol

from electrons filling the orbitals?

6:36 AM

what?????

what?

"why is there Cl•"?

because god made them?

sorry, but i have no clue what on earth you are saying

how do i know what you want me to answer

we are talking about NH3 and HCl not lone chlorine atoms

oh i'm talking about lone chlorine atoms

sorry for the confusion

6:38 AM

.... you've gotta say that you changed the topic, please

yes sorry

anyway, it is not that Cl. wants to become Cl-

it is that, if you place an electron near a lone chlorine atom, it turns out that the electron likes hanging around the chlorine atom

because of the positively charged nucleus

uh, how is that different from Cl• wanting to become Cl-?

the presence of the lone electron.

whatever, then why does the electron like it?

6:40 AM

because it will have a lower energy if it goes closer to the chlorine nucleus

and then why would an extra electron (Cl^2-) not like it?

because then it has to go into a higher energy orbital

which is... 4s

whereas the first one is happy and comfortable sitting in 3p

still lower than hanging around?

yeah

at least, that's what the electron affinity tells us

then why does it still leave?

6:43 AM

when does it leave?

you talking about Cl- turning back into Cl.?

oh

i'm talking about Cl^2- becoming Cl-

oh

sorry, i misinterpreted "still lower than hanging around"

i thought you were talking about 3p. well, nah, 4s is not still lower than hanging around

i thought hanging around is basically infinite

hanging around is defined as 0

i know, the energy is 0, but the "orbital number" is infinite

and every orbital is negative right

6:46 AM

that's in hydrogen

:o

where does the color of chlorine (Cl2) come from?

[new topic]

(if anybody else is reading this, i know this is somewhat flawed, because the electron affinity isn't the same as the energy of the orbital, but whatever)

um, i have no idea actually

maybe the electrons jumping from the HOMO to the LUMO?

the LUMO is antibonding though

it is possible

that was my first thought, but i have no idea

and i thought only ultraviolet can split the Cl2

meaning that only ultraviolet can promote the electron

6:51 AM

excited state of chlorine is not necessarily the same as dissociation

don't you promote an electron from HOMO to LUMO to dissociate chlorine?

no

that wouldn't work

then how?

user image

you see this diagram? the bottom of the lowest curve, that is the ground state of Cl2 (neglecting zero point energy)

the dissociation corresponds to the energy when the bond length is infinite - which is where the graphs plateau off to the right

however, there can also be electronic excited states which are not quite enough for dissociation - such as the valley of the second-lowest graph (where it says A 3Pi_u)

how would the MO of the state good for dissociation look like?

6:55 AM

as for how does it dissociate, like in terms of mechanism, i think that that is more of a vibrational excitation than an electronic excitation, but i don't know for sure.

interesting

because promotion of electrons means you jump from one curve to another

but moving from one point on a curve to another point on the same curve

involves vibrational levels

user image

the different vibrational levels are in red

and the blue curve represents one electronic state only, i.e. no movement of electrons

from orbital to orbital

Morse potential

The Morse potential, named after physicist Philip M. Morse, is a convenient interatomic interaction model for the potential energy of a diatomic molecule. It is a better approximation for the vibrational structure of the molecule than the QHO (quantum harmonic oscillator) because it explicitly includes the effects of bond breaking, such as the existence of unbound states. It also accounts for the anharmonicity of real bonds and the non-zero transition probability for overtone and combination bands. The Morse potential can also be used to model other interactions such as the interaction between...

i thought if you promote it to the 4th state then it will dissociate by itself

@orthocresol

@user34388 i think there's still a tiny region where it could admit bound states, although it is difficult to see clearly on this small graph

there are certainly some electronic states which don't admit bound vibrational states at all

so that would be possible, i suppose

that would not necessarily correspond to HOMO-LUMO transition though, it could be any weird combination of promotion of electrons

I see

7:03 AM

i don't know why it's coloured, so far my google attempts have failed me

:/

[new topic] would i be correct in saying that Cu^2+ exists both as [Ar] 3d9 and [Ar] 3d8 4s1?

well, it could certainly be 3d8 4s1, but probably not to any appreciable extent

maybe at any given time, in 1 mole of Cu^2+ ions, a handful of them are 3d8 4s1

3d9 is just more stable

sure, without the 3d8 4s1 the solution would not have color

@orthocresol

the color is not due to 3d->4s promotion though

it is electronic transitions within 3d

:o

7:09 AM

have you heard of crystal field theory?

no

there's lots of it on SE, if you hold on, i can try to find a good one.

17

Q: Why are some salt solutions coloured?

I notice that salt solutions of $\ce{NaCl}$ and $\ce{KCl}$ are colourless while those of $\ce{CuSO4}$ and $\ce{FeSO4}$ are coloured. I got as far as figuring that it has to do with the transition metal ions, but I can't explain why the salt solution of $\ce{ZnSO4}$ is colourless even though zin...

color transition-metals

what is the significance of the 3 in 3d?

it just means that in the hydrogen atom that orbital has n = 3

what is n?

7:12 AM

i mean, technically n is still 3 in any atom

n is the principal quantum number, which dictates the energy of the orbital in the hydrogen atom

earlier we said that the free electron has energy 0

the orbital energies are proportional to $-(1/n^2)$

so 3s and 3p have the same energy?

in hydrogen, yes, (also if you ignore relativity, spin orbit coupling, hyperfine coupling and other issues)

but this degeneracy is lifted in any species with more than one electron.

i see

therefore in helium onwards 3s < 3p in energy

chemistry is confusing, eh?

i always feel like we don't really know that much about it at all..

yea indeed

1 hour later…

8:34 AM

sciencedaily.com/releases/2016/09/160915132440.htm

8:49 AM

What is a bond in MO theory?

when there are electrons occupying the bonding orbitals

But electrons are not localized

then how can bonds be localized?

By the way, here is a promotion for my question:

2

Q: All resonance structures of the hydrogen molecule

This article written by our dear user Jan says that "a professor of mine claimed to have drawn some 18 (or was it 80?) different resonance Lewis structures". Please reproduce those resonance structures of the hydrogen molecule. If nobody is able to come up with that many, the answer with the mo...

molecules resonance hydrogen

There are not localised as in you cannot pinpoint where they are. However, MO theory means you can assign a probability on where you can find the electrons in a region

fair enough

and because of the wavefunctions of the molecule, these regions of probability have different shapes

The MOs in MO theory add together to approximate the wavefunction of the molecule

2 hours later…

10:38 AM

do ionic compounds conduct electricity through ions or electrons?

10:54 AM

in their solid state they don't conduct electricity

@MartianCactus electrons

they also undergo electrolysis

but someone once told me that ions conduct electricity too

and that ionic compounds use ions to conduct

i'm not sure then

also why dont they conduct in solid state?

iron can conduct in solid state

iron is metal, not ionic

like electrons can still travel

11:01 AM

user image

user image

The first picture is metal; the electrons are delocalized

The second picture is ionic compounds; the charges are localized

user116211

@MartianCactus What do you want to know about that?

so why can electrons travel in liquids and gaseous state?

its the same as saying that electrons can travel in non-metals which are in liquid state

thus saying that these can condut electricity

user116211

@user34388 They are not always localised.

@MAFIA36790 fair enough. those 3c2e things

@MartianCactus I guess I'll leave it for others to answer sorry

oh ok

thanks tho

do ionic compounds conduct electricity through ions or electrons?

repeating question so that people can see it

user116211

11:15 AM

Any-ways, for the general purpose, electrons can go from one atom to other because there is a non-zero probability amplitude for this. That's how conduction takes place.

xD i understand almost nothing of what MAFIA said

i am a 10th grader soo

@MartianCactus electrons are not tiny balls

their location at a given instant is random

but they have a high probability to be around the nucleus

@MartianCactus I think the answer is both. By electron near the electrodes, and by ions within themselves.

@MartianCactus the keyword is: not all ionic compounds can conduct electricity via ions

some can, some cannot

@orthocresol :o what cannot?

um, table salt?

11:23 AM

I thought chlorine is generated by electrolysis of table salt

you can hook up table salt to a battery and see if anything happens

thats because it is a solid?

it is electrolysis of a concentrated solution of NaCl that generates the chlorine gas

the ions in NaCl(s) are not mobile, hence they do not move.

when you dissolve NaCl, the ions can swim wherever they want

but ionic compounds in molten states and aqueous states do conduct electricity

i've stated that already

that is not contradictory to anything i said

11:25 AM

alright

i wasn't talking to you anyway - i was addressing the idea that ionic compounds can conduct electricity

so nothing at fault with what you said

@orthocresol well, you said "some (ionic compounds)" which implied to me that it is dependent on the species

oh, well, in liquid/solution i suppose everything conducts.

in solid state, it depends

@orthocresol what can?

um, I'll give you the names, you can look them up if you are interested..

11:30 AM

sure

alpha-AgI, beta alumina, yttria-stabilised zirconia,

the famous high-T superconductors, like YBa2Cu3O7, those are also ionic

I think we have scared @MartianCactus away by introducing wave-particle duality

ReO3 also conducts

although that is electronic conductivity, not ionic

hullo @Loong

@orthocresol hi

!!img/ipso-dichlorobenzene

11:34 AM

No result found.

is there any ipso- compounds?

well, that does not make sense

ipso implies on the same carbon

but a benzene ring can only have one substituent on one carbon

that could be positively charged

the term ipso is more commonly used to describe the attack of an electrophilic species

like how one says OH is o,p-directing

xd know what the theory of orbital things that ur talking about i was just afk

11:36 AM

-SiMe3 for example would be ipso-directing

@MartianCactus so my answer is "both, by electron near the electrodes and by ion within themselves"

so what does the medium of conduction depend on? Why do some conduct through ions and some through electrons?

i thought brine conducted through ions

@MartianCactus crystal structure, band structure

yes, but by electron near the electrodes

oh

whats band though?

@user34388 ?

11:38 AM

@MartianCactus between the electrode and the ion is electron transfer

@MartianCactus solid state equivalent of mo diagram

but then they wouldnt be ions anymore

i have no idea what mo diagram is xd

i know so less..

what would they be?

they will gain/lose electons at electrodes and wont be charged anymore

yes, that is electrolysis

which is why chlorine is generated when you charge brine

11:42 AM

@MartianCactus precisely, which is why $\ce{2Cl- -> Cl2 + 2e-}$

@orthocresol And that's why this question makes no sense. ;-)

@Loong why?

@user34388 The electrolysis of NaCl yields Cl2. But HCl is produced in the question.

@Loong seems like he wants to have Na+ -> Na at the cathode and OH- -> O2 at the anode

oh well

all the best to him i guess

@Loong I guess H2 + Cl2 -> 2HCl

11:50 AM

but

you said that ions do conduct in electrolysis right?

but the ions, after they reach the electrodes are not even ions anymore

@MartianCactus
electrode <-1-> ion <-2-> ion <-1-> electrode

@user34388 Yes, you could burn the created H2 and Cl2 (both from electrolysis) again to HCl, but that would be a waste of energy.

where 1 is electron transfer

@MartianCactus that is correct

??

-1-?

never mind

11:52 AM

what does that mean

so as you notice, the ions become neutral near the electrodes

the symbols arent translating

do i have to download something?

<-1-> is an arrow labelled with 1

<--> is an arrow

@user34388 true

so what does 1 mean?

i said 1 is electron transfer

11:54 AM

actually i have to go to tuition

oh

user116211

@MartianCactus Let you number the adjoining atoms and take them as the basis of the state: $|n\rangle\;.$ So, the state of the electron $|\varphi\rangle$ can be expressed as: $$|\varphi\rangle = \sum_n |n\rangle {\langle n|\varphi\rangle} =\sum_n |n\rangle \mathrm C_n \;.$$

then how can ions conduct of they are no longer ions???????

cuz they get the electrons and become neutral

user116211

Write the Hamiltonian equations:

\begin{align}\mathrm i\hbar~\frac{\mathrm {d C}_{n-1}}{\mathrm dt} &= E_0~\mathrm C_{n-1} - A~\mathrm C_{n-2}-A~\mathrm C_{n}\\ \mathrm i\hbar~\frac{\mathrm {d C}_n}{\mathrm dt} &= E_0~\mathrm C_n - A~\mathrm C_{n+1}-A~\mathrm C_{n-1}\\ \mathrm i\hbar~\frac{\mathrm {d C}_{n+1}}{\mathrm dt} &= E_0~\mathrm C_{n+1} - A~\mathrm C_{n}-A~\mathrm C_{n+2}\\ & \vdots \end{align}

omg the symbols arent translating

@MAFIA36790 he is a 10 grader

user116211

11:56 AM

where $E_0$ is zero of the energy; the energy of an un-leaked electron and $A$ is a non-zero constant.

@MartianCactus they dont. they go away. chlorine for example becomes gas and leaves the system

user116211

@user34388 O.o

so that the remaining thing can conduct electricity

this is what it looks like prntscr.com/cio1sk

user116211

Still, I would complete it....

11:56 AM

but you said that ions conduct in the electrolyte

user116211

To solve these for definite energy states, put $$\mathrm C_n = a_ne^{-\mathrm iEt}{\hbar}\;.$$

Computing these, you would get $$a(x_n) = e^{\mathrm ikx_n}\;.$$

For each $k$ and $a,$ you would get the probability-amplitude as $$\mathrm C_n = e^{-\mathrm i\left(-kx_n+ \frac{Et}{\hbar}\right)}.$$

@MartianCactus yes, so once the "neutralized" ions leave the system the ions can continue their destiny

all the ions get neutralized

thats what electrolysis means

the tearing apart of the entire misture

@MAFIA36790 you can't construct the state of an electron out of a basis set of atoms :)

because ions, being atoms still can move like electricity due to their charge

actually lets come to the original question- "When do ionic compounds conduct through electrons and when with ions"

11:59 AM

@MartianCactus it isn't like all of the ions get electrolysed instantly

it is a slow and painful process

yeah actually

oh

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Sep '1616

The Periodic Table

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