The Bohr Model of the atom and Atomic Emission Spectra: Atomic Structure tutorial | Crash Chemistry

This video explores Bohr's atomic model and how Bohr used hydrogen's emission spectra to create his model of the atom. The video also looks at the relationship of the Bohr model to the quantum mechanical model of the atom: What was revolutionary about the Bohr model that led to the quantum mechanical model, and what parts of the Bohr model had to be discarded.
-More on Emission Spectra | Wiki- Wikipedia 3 July 2016
"The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore, spectroscopy can be used to identify the elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances. ...
In physics, emission is the process by which a higher energy quantum mechanical state of a particle becomes converted to a lower one through the emission of a photon, resulting in the production of light. The frequency of light emitted is a function of the energy of the transition. Since energy must be conserved, the energy difference between the two states equals the energy carried off by the photon. The energy states of the transitions can lead to emissions over a very large range of frequencies. For example, visible light is emitted by the coupling of electronic states in atoms and molecules (then the phenomenon is called fluorescence or phosphorescence). On the other hand, nuclear shell transitions can emit high energy gamma rays, while nuclear spin transitions emit low energy radio waves.
The emittance of an object quantifies how much light is emitted by it. This may be related to other properties of the object through the Stefan-Boltzmann law. For most substances, the amount of emission varies with the temperature and the spectroscopic composition of the object, leading to the appearance of color temperature and emission lines. Precise measurements at many wavelengths allow the identification of a substance via emission spectroscopy.
Emission of radiation is typically described using semi-classical quantum mechanics: the particle's energy levels and spacings are determined from quantum mechanics, and light is treated as an oscillating electric field that can drive a transition if it is in resonance with the system's natural frequency. The quantum mechanics problem is treated using time-dependent perturbation theory and leads to the general result known as Fermi's golden rule. The description has been superseded by quantum electrodynamics, although the semi-classical version continues to be more useful in most practical computations."
Wikipedia contributors. "Emission spectrum." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 18 Jun. 2016. Web. 3 Jul. 2016.

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Who came here 'cause of their chemistry teacher?

[@dominicestebanrice7460]

I've watched literally dozens of videos on this topic but none as good as this; a masterpiece of science explication.

[@sk8terbluetoo]

Great! In class I had totally missed how Bohr was connected to emission spectra. This is a perfect explanation.

[@g3toutth3way]

Thanks man! My teacher shared this with our class. Good stuff!

[@1hullofaguy]

You are a truly talented power pointer!

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To the point, Crisp, crystal clear, great animations - All these make a great educational video. And this surely is one!

[@CrashChemistryAcademy]

Thank you!

[@Liboo52]

Beautiful video. The graphics are so clean and the information is given so clearly. A pleasure to watch because I learned so easily

[@iambicgatchster1852]

Thanks for the clarity. Lot's of good information, well explained. It gave me a "aha!" moment, trying to understand the transition from earlier models of the atom to the quantum mechanical model.

[@ismailbeddiar4288]

This video should be viewed by all students of the school. In fact this video summarizes all the works of ancient science. thank you again

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Amazing job teaching something so complicated

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[@CrashChemistryAcademy]

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[@farouqalsalih619]

This video was very helpful. Thank you very much!

[@philoadriensson9850]

most excellent. informative regarding emission spectra itself and I have not found any decent explanation of the connection between emission spectra and what Neils Bohr did. Thank you so much for your clear explanation here.

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beautiful video. perfect graphics. thanks so much for your effort.

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Great explanation & very pertinent animation.

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[@CrashChemistryAcademy]

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extremely informative. Thanks.

[@lianawang4219]

Very helpful, thanks!

[@davemort83]

I'm a middle school math and science teacher and this video provides a really useful resource for students to help them tie together the notion of atomic spectra and the bohr model. Thank you!

[@CrashChemistryAcademy]

Thanks so much. It is always very gratifying to hear from other teachers.

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[@CrashChemistryAcademy]

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I wrote almost anything that you said since I'm a slow learner and it took me 2 hours to write it all but it was worth it! Thank you😁

[@CrashChemistryAcademy]

i have transcripts for most of my videos. If you write to the email in the 'about' section of my channel, I would be happy to send you any transcript.

[@devilgamingyt388]

👍 good job

[@h2energynow]

Awesome, loved when you used hydrogen as an example. CEO H2 Energy Now

[@CrashChemistryAcademy]

sorry for the belated reply, but if you really are the CEO of a company called H2 Energy Now (or even if not), I have two questions: 1) it seems to me we could have an endless supply of H2 if we just hydrolyzed water using solar collectors. There would be zero carbon emission for the energy used to produce H2 gas once the panels are set up. Has anyone tried this? 2) If we rely too much on H2 as an energy source, would it create environmental issues due to an increase in average humidity? (On the other hand, I imagine this would be far preferable to global warming.)

[@DrAdityaReddy]

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[@johnpaulsecond4626]

beautifully done; there must be a similar diagramatic chart for each element on the Periodic Table somewhere; how these EM spectra tie in and explore unstable excited Free Radicals is my next question.

[@CrashChemistryAcademy]

Thanks! If you search for "emission spectra periodic table" you will see a bunch of images of emission spectra of all the elements. Any free radical should have a slightly different, and therefore identifiable, spectra than whatever stable non-radical it came from. The electron deficiency would be on the outer valence energy level, and so would certainly affect energy absorption/emission. NO2 would be a good radical to search for.

[@mostafaismail43]

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[@CrashChemistryAcademy]

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[@CrashChemistryAcademy]

You're welcome!

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Thanks for teaching

[@CrashChemistryAcademy]

Thanks for watching!

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[@CrashChemistryAcademy]

Thank you!

[@johnpaulsecond4626]

when we look at the central axis of an EM wave transversely, where the three perpendicular axes (x, y, z) intersect, and we look head on as it were into that oncoming wave of electrical and magnetic ossilations -as if into the cross hair of its trajectory - the Bohr atomic model seems to fit nicely into that eye view, expand that transverse view of the wave, and fill in the gaps between the epicentre of the wave (? neutron) and the outer orbital states. Does that sound right ?

[@CrashChemistryAcademy]

I guess I would think any connection between a particular perspective of a periodic function and the Bohr model would be a coincidence. Bohr came up with quantization (which Einstein showed to exist with photons) but that is the opposite side of the wave/particle coin. It was de Broglie who put Bohr's quantized electron on a wave footing, which became the quantum mechanical model via the Schrodinger equation, a fairly significant departure from Bohr's model other than the quantization, which did remain a central theme of quantum mechanics (and is why it is called "quantum" mechanics).

[@user-wm7lx3yo1u]

I have a question that i didn't get a clear answer, the question is how the light can be wave and a particle ? I know about ( photoelectric effect ) Einsten's experienes, but i don't understand how he reached his result. I hope you can help me.

[@sohojpora2697]

thank you for easy and nice lecture. one question is we found electron of H in first orbit that means n=1, K she'll. but how how electron came from upper orbit?

[@CrashChemistryAcademy]

When hydrogen's single electron absorbs energy, it jumps to a higher energy level, and then it will jump back down to the first energy level while emitting light.

[@Zanodia]

What was the initial event that cause the first electrons to emit photons?

[@CrashChemistryAcademy]

The absorption of energy. Any kind of energy, light, electricity, heat, as long as it is the right amount of energy. The electron absorbs that energy, and then releases the same energy as a photon.

[@balajialande1334]

Awesome

[@CrashChemistryAcademy]

Thanks!

[@dtr3197]

This video is great - wasn't Einstein's Nobel prize for the photoelectric effect? (this is showing light behaving like a particle- but the momentum bit was de Broglie)

[@CrashChemistryAcademy]

You're right, I stretched it a bit. Einstein did not say light had momentum, he did show it to have the properties of a particle, as you say, due to a photon being able to "kick out" an electron from the surface of a metal, which mimics the behavior of something with momentum, and so I threw in the momentum to drive home the point. I did not know that de Broglie specifically addressed momentum. Good to know, thanks.

[@dtr3197]

@@CrashChemistryAcademy great, thanks I'm a UK based physics teacher and this video leads very nicely on from the photo electric effect and work function 👍 I've recommended to my students

[@CrashChemistryAcademy]

@@dtr3197 Thanks! Do you tech atomic structure in introductory physics over there? (I'm assuming you are teaching an intro class...) Here (US) it is usually taught in chemistry for intro classes.

[@dtr3197]

@@CrashChemistryAcademy It's A-level, I'm not sure of the exact US equivalent. I think in the UK we have our 'learners' specialise a bit earlier, so it is probably equivalent to university foundation level - the A-levels are courses to allow entry to university. If you look up AQA A-level physics you might be interested to see the crossover of content 😁

[@CrashChemistryAcademy]

Thanks for the AQA A-level physics reference. I had fun looking at a textbook contents and it looks more interesting than what I've seen in US physics texts! Our equivalent to A-level takes many guises, from IB (which I believe exists in the UK), to "honors" classes to "AP" classes and likely others. The school districts around the country are fairly independent and so come up with different ways to address university prep.

[@adrianyeoman2587]

Great video as many have said. I have a question which may show my ignorance. If hydrogen has just one electron jumping from one level to the next, eg n3 to n2 how can it produce different colours in its emission spectra. Surely that would require several electrons jumping around. Can anyone explain this for me? Adrian

[@CrashChemistryAcademy]

Great question! Yes, a single atom of hydrogen with a single electron transitioning from n3 to n2 will always emit the same specific color. However there are two qualifications with that. The first is that the transition is momentary and so it can continue to absorb energy again and again and emit light. If it absorbs varying amounts of energy (as allowed by its quantization), then it can jump to varying allowed energies and the transition back down would emit light specific to the transition. So over a short time, a single atom could emit (in the visible range) the four colors shown in the video, in particular see 4:00 to 4:15 to clarify. The second is that when observing hydrogen's emission spectra, we are observing the result of adding energy to many quintillions of atoms of hydrogen (the atoms in the electrified gas tube shown in the video, 0:25, for example). All those atoms combine to produce a constant visible emission of the four colors. Note that hydrogen also emits infrared and ultraviolet as well, depending (again) on the amount of energy absorbed and the size of the transition back down.

[@BreuerTech]

The process happens for ridiculous numbers of electrons as even in a small amount of hydrogen there would be unconscienable numbers of electrons. Each electron can absorb and release a different quanta.

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[@vicentesayson2990]

Hi, It's been a long time since this video have been posted but I have a question and I'm hoping to get an answer from you sir. "Where'd you get the Electron Energy in Hydrogen?", how can you end up with -2.18x10^-18 J. I wonder if there's an equation that would help me to solve that so I can identify Electron Energy of any Atoms." Thank you very much sir :)

[@CrashChemistryAcademy]

The number is derived from Rydberg's analysis of the frequency of light emitted from hydrogen and the resulting equation he derived. If you look up "Rydberg Formula" you will find more information. Specifically, -2.18x10^-18 J came out of converting into joules the number that Rydberg came up with for frequency.

[@kushkitten]

Does n=3 to n=2 always emit red? Does n=4 always emit a certain colour? etc? Is there a way to predict which type of radiation on the spectrum a certain n to n will emit? eg. can I predict which region n=6 to n=3 would fall in? or n=6 to n=1?

[@CrashChemistryAcademy]

The equation at 7:35 tells you the exact wavelength emitted for any n to n transition but only for hydrogen. For other atoms, the Rydberg equation is used, which can be looked up on the internet or textbook.

[@lorechadominic4920]

Thanks for this! How do u subtract Shouldn't it be nf - ni Look like you have subtract ni - nf Please explain?

[@CrashChemistryAcademy]

Yes, the sequence in textbooks is given as nf - ni. This results in a positive value, which is correct for the energy of a photon, the emitted light. I reversed it to show that the energy emitted comes from the change in ni - nf, or excited state - ground state. The result is the same, just opposite in sign, but I meant to convey that it is the magnitude (absolute value) of the difference that is the energy of the emitted light. Sorry if that was not clear.

[@lorechadominic4920]

Thanks I go it now.

[@rosedwilson402]

well maybe i come up with some crap but here it goes: bohrs raise to many of questions i can now see why bohrs modell no longer exits in new school books if you go after his an electron would be a photon or a photon with attribues but the double slit and wave measurements show something else some could come up with even more of questions to bohrs modell, it rather sounds that this was a idea from his experiment planck got the best ideas for this no photons dont exits the electromagnet spectrum there would be a red, green, blue photon and others and have no answer for other forms while we know there more wave form in the spectra the spectrum shows that all kind of "free energie" has this discrete waves there is an entire spectrum a other proof is that all kind of electric flux can be converted into this form of wave (instead of only "photons") so again the spectrum has answers for this im not so certain if the spectrum doesnt have a answer for mass or particle because some could its a particle moving in a wave form, the wave would actually give it a momentum so i wouldnt assume or neccesary say the spectrum doesnt have a answer to this question or exclude those very specfic its the oposite planck has the answer in E it could be seens as a mass, particle or a particle moving in sine wave form why not ?

[@lexismedia761]

Infrared rays

[@scootersinister3745]

If I’m given a spectrum how can I identify the element

[@CrashChemistryAcademy]

The elements' spectra are all experimentally derived, so you would have to compare your spectrum with the known spectra of all the elements to see what it matches.

[@rehmani111]

n5-n4 infrared region.

[@CrashChemistryAcademy]

Yes!

[@ashmarie4079]

I was given this video as an assignment, can anyone help me get a start on these questions? Calculate the wavelength of light released when an electron drops from the 2nd shell to the 1st shell. In what region of the electromagnetic spectrum is this light? Calculate the wavelength of light released when an electron drops from the 4th shell to the 3rd shell. In what region of the electromagnetic spectrum is this light? Im very confused.

[@CrashChemistryAcademy]

At 7:31 the equation you need to use pops up. The n in the equation is the shell number. If you watch from 7:31 to 8:25 it explains what to do with the different n values (shell numbers). Once you get the energy, you can either do a google search to find what region of the EM spectrum that is, or you could convert the energy to wavelength using the equation wavelength = hc/energy, with h being Planck's constant and c the speed of light. And then you could do the same, an internet search for the EM region of the wavelength. Either way you will get the same answer.

[@AK-di4rv]

Is the answer to n=4 to n=5 red?

[@CrashChemistryAcademy]

n = 5 to n = 4 would produce infrared radiation. The energy difference is less than that of red (the lowest energy color) and so it would be infrared -- "infra" is a latin root for "below."

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[@CrashChemistryAcademy]

ขอขอบคุณ

[@ignatiusprasad3894]

It seems you are telling that there are multiple electrons for a hydrogen atom. But isn't there only one electron in the hydrogen atom.

[@CrashChemistryAcademy]

A single electron which can exist at multiple discrete energy states.

[@chimmys577]

I have to take notes :(

[@CrashChemistryAcademy]

Sounds like you have a good chem teacher...

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[@frederickfergal7924]

Excellent and beautiful video. I suggest you see some interesting videos on SALEH THEORY-com about behaviors of photon.

[@returnofthemomos]

First!

[@nightb0t1100]

Boring....