Some Basic Line Spectrum and Chemistry Questions I Have

[Owelode]

I've never really taken any chemistry before so I'm currently taking a class and the more I learn about it, the more interesting it becomes. However, I do have a few questions (you might find simple) that are kind of bugging me as we begin to progress through the chapters...


1. When trying to make electrons produce photons, does the color of the light emitted depend on what temperature you use or how you excite the atom?


2. If you have an electron in the, let's say, 1st energy level and it absorbs enough energy to get to the 5th energy level or anything above the 1st level, what happens to the first level? There's only 1 electron left there...or does the atom just become unstable for a bit?


3. Okay, about photoionization...what's up with it? What happens to the electron that was lost? If you were to isolate one single atom or there were no other atoms it could bond with, what would happen?


4. So I didn't quite grasp what the continuous spectrum was. I know the line spectrum...but what relations does the continuous spectrum have with it?


5. I'm not so sure on how the orbitals would look on an atom. Are electrons intercepting each other's orbitals? Could you bring the nucleus of such a HUGE atom that it makes the electrons of another atom attract to it also? (so that maybe they crash?)


6. Alright, does the quantum mechanical model of an atom tell you where a particular electron you're looking for is or does it tell you where you're likely to find an electron? (Are electrons always in orbitals?)


7. So if an electron is in the let's say...Px orbital, will it always stay in the Px orbital or will another electron (from any orbital/energy level) come and take turns with it? If the electron in a specific orbital does change, does that mean any electron from any energy level can take its place?


8. Why does the electron emit an amount of energy that is the "difference between levels" instead of keeping it simple and emitting what it absorbed to reach those levels? Or is that what the difference is...?


9. Okay, so why would an atom be unstable if it doesn't have its valence shell completely filled? It has an amount of electrons equal to the amount of protons, so shouldn't it be stable...? I'm thinking this has to do with having too much energy burdened on an electron, so if that's it, why can't the electron just emit the energy out as photons?


10. About isotopes: Why would the number of neutrons affect the element and make it unstable if neutrons are neutrally charged? What does mass do other than make the atom heavier? Why would more mass make the atom unstable, in other words.


11. On Physical/Chemical changes: Would dissolving sodium chloride in water be physical or chemical? NaCl is a compound which has its bond broken apart in water--chlorine is separated from sodium (for crying out loud!) and they attach to H₂O molecules. Then when you evaporate water, sodium and chlorine bond again...which I would think would be another chemical change?


12. Waves/Radars: If a radar detector is a receiver, how would a radar detector detector work? Wouldn't this mean the radar detector also emits some sort of radiation?





That's all I've got for now. I apologize for bombarding you guys with so many questions (like a nuclear reaction! :D), but I'd really like to know this and understand--hopefully--every bit of it.

Thanks.

 

[Borek]

Wow. A lot.

1. When trying to make electrons produce photons, does the color of the light emitted depend on what temperature you use or how you excite the atom?

To some extent it can - but the most important thing is the atom itself. In higher temperatures there are higher chances of exciting atom to higher energy levels, thus photons emitted go to the bluish part of the spectru,

2. If you have an electron in the, let's say, 1st energy level and it absorbs enough energy to get to the 5th energy level or anything above the 1st level, what happens to the first level? There's only 1 electron left there...or does the atom just become unstable for a bit?

There is a hole. You may call the atom electronic configuration unstable.

3. Okay, about photoionization...what's up with it? What happens to the electron that was lost? If you were to isolate one single atom or there were no other atoms it could bond with, what would happen?

Electron 'just' flies away. In general it will be just as happy as a single particle in the space. In the presence of other atoms or molecules it will sooner or later find a new place.

4. So I didn't quite grasp what the continuous spectrum was. I know the line spectrum...but what relations does the continuous spectrum have with it?

None. That is - both are emitted, but mechanism behind is completely different.

5. I'm not so sure on how the orbitals would look on an atom. Are electrons intercepting each other's orbitals?

They occupy the same space...

Gotta go for a moment. Perhaps someone else will be able to help more.

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methods

 

[alxm]

Continuing where Borek left off..

6. Alright, does the quantum mechanical model of an atom tell you where a particular electron you're looking for is or does it tell you where you're likely to find an electron? (Are electrons always in orbitals?)

It tells you the probability of finding it at a point in space, for every point in space.
Atomic/molecular electrons are either in orbitals, or they're not atomic/molecular electrons. They're free electrons whizzing about the vacuum.

7. So if an electron is in the let's say...Px orbital, will it always stay in the Px orbital or will another electron (from any orbital/energy level) come and take turns with it? If the electron in a specific orbital does change, does that mean any electron from any energy level can take its place?

They switch places, but only ones that have the same spin can switch places with each-other, because you can't have two electrons of the same spin in the same orbital, nor can (bound) electrons change their spin. (spin is conserved)

8. Why does the electron emit an amount of energy that is the "difference between levels" instead of keeping it simple and emitting what it absorbed to reach those levels? Or is that what the difference is...?

En electron will emit the difference in energy between the energy levels it's transitioning between. That might be the same as the energy absorbed when it was excited to that state, but it could be less. It could even be more.

9. Okay, so why would an atom be unstable if it doesn't have its valence shell completely filled? It has an amount of electrons equal to the amount of protons, so shouldn't it be stable...? I'm thinking this has to do with having too much energy burdened on an electron, so if that's it, why can't the electron just emit the energy out as photons?

Stable, compared to what? What they're talking about here is the stability of chemical compounds. In which case, for instance, a hydrogen molecule has less energy (=is more stable) than two isolated hydrogen atoms. So a hydrogen atom (and most isolated atoms, except noble gases) is chemically unstable. It will often react to form a compound. But it's not 'unstable' in the sense that an excited atomic configuration is; it can't bring itself to a lower energy level.

10. About isotopes: Why would the number of neutrons affect the element and make it unstable if neutrons are neutrally charged? What does mass do other than make the atom heavier? Why would more mass make the atom unstable, in other words.

And that's nuclear stability. This has to do with the nuclear forces holding nuclei together, which is independent of charge. From a chemical or atomic-molecular standpoint though, the effect of extra neutrons is more-or-less limited to the change in weight.

11. On Physical/Chemical changes: Would dissolving sodium chloride in water be physical or chemical? NaCl is a compound which has its bond broken apart in water--chlorine is separated from sodium (for crying out loud!) and they attach to H₂O molecules. Then when you evaporate water, sodium and chlorine bond again...which I would think would be another chemical change?

Solvation and precipitation fall classically into the category of chemistry. But really, there's not much sense in putting labels on it. Since quantum mechanics came around, chemistry is more-or-less nothing other than a highly specialized branch of physics.

12. Waves/Radars: If a radar detector is a receiver, how would a radar detector detector work? Wouldn't this mean the radar detector also emits some sort of radiation?

They do, it has to do with how the super-heterodyne receiver they use works.

 

[Owelode]

Thanks for answering my questions. :)

To some extent it can - but the most important thing is the atom itself. In higher temperatures there are higher chances of exciting atom to higher energy levels, thus photons emitted go to the bluish part of the spectru,

So would this mean that if you were to attempt exciting a specific atom (that emits a specific colored light at high temperatures) at low temperatures, the photons (if any were emitted) would produce a different color light?

Stable, compared to what? What they're talking about here is the stability of chemical compounds. In which case, for instance, a hydrogen molecule has less energy (=is more stable) than two isolated hydrogen atoms. So a hydrogen atom (and most isolated atoms, except noble gases) is chemically unstable. It will often react to form a compound. But it's not 'unstable' in the sense that an excited atomic configuration is; it can't bring itself to a lower energy level.

What I meant was an atom that is unstable, like Chlorine for example, has 7 electrons in its valence shell. But overall, a Chlorine atom with 17 electrons also has 17 protons, which should make it balanced in that sense. It's not stable, though...and that's because it needs 1 more electron? Is there too much energy in the last shell for those 7 electrons? Couldn't the electrons emit that extra energy as photons?


I think I understand what you said, though (or I hope so). The atom wouldn't be able to make itself stable because electrons can't bring themselves to lower levels? But, why not...if when you excite an atom, electrons gain so much energy they jump to higher levels and come back after they've emitted energy as photons? The valence electrons of Chlorine already have too much energy...can't they emit that as photons?


Heh, I feel like I'm missing something really obvious here.

Solvation and precipitation fall classically into the category of chemistry. But really, there's not much sense in putting labels on it. Since quantum mechanics came around, chemistry is more-or-less nothing other than a highly specialized branch of physics.

I was actually told that dissolving ionic compounds would be considered a physical change since their bonds are weak and (using the salt dissolving in water example) when you evaporate water, the salt left over somehow leads to the salt never being broken apart in the first place or something like that. But I still believe it's chemical regardless of "weak bonds" and all that. I was just making sure I wasn't the only one who thinks they're crazy. I also agree with that last statement (though my teacher would probably be outraged).


So once again, thanks! :D

 

[Borek]

So would this mean that if you were to attempt exciting a specific atom (that emits a specific colored light at high temperatures) at low temperatures, the photons (if any were emitted) would produce a different color light?

Each atoms has a specific list of photons it can emit - see for example http://en.wikipedia.org/wiki/Hydrogen_spectral_series. You will never see photons with energies that are not on these lists, and each of these photons has well known energy (that is - color, if it happens to be in the visible part of spectrum). Relative number of photons of different energies emitted depends on the temperature.

What I meant was an atom that is unstable, like Chlorine for example, has 7 electrons in its valence shell. But overall, a Chlorine atom with 17 electrons also has 17 protons, which should make it balanced in that sense. It's not stable, though...and that's because it needs 1 more electron? Is there too much energy in the last shell for those 7 electrons? Couldn't the electrons emit that extra energy as photons?

Chlorine atom - if separated from everything else - is quite stable. However, if there is anything around, chances are it can get more stable configuration, getting additional electron. If it can - it will. If it can't - it will be perfectly happy with its basic state.

I think I understand what you said, though (or I hope so). The atom wouldn't be able to make itself stable because electrons can't bring themselves to lower levels? But, why not...if when you excite an atom, electrons gain so much energy they jump to higher levels and come back after they've emitted energy as photons? The valence electrons of Chlorine already have too much energy...can't they emit that as photons?

No, they can't fall down as all lower energy levels are already occupied. Each electron in the atom is described by four quantum numbers, and Pauli exclusion principle states that no two electrons in an atom can have all quantum numbers identical. This means there are limits on the number of energy levels.

I was actually told that dissolving ionic compounds would be considered a physical change since their bonds are weak and (using the salt dissolving in water example) when you evaporate water, the salt left over somehow leads to the salt never being broken apart in the first place or something like that. But I still believe it's chemical regardless of "weak bonds" and all that. I was just making sure I wasn't the only one who thinks they're crazy. I also agree with that last statement (though my teacher would probably be outraged).

Some changes are clearly chemical, some are clearly physical - but there is a gray area of changes that are not easily classified.

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[Owelode]

Oh, okay. I understand now. Seems like I had the wrong ideas on a lot of things. :S

Thanks a bunch. :D

 

[Borek]

Note: part of the information I have posted is slightly simplified. Don't treat it as a definite truth

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methods