Sciencemadness Discussion Board

Why does hydrogen emit several spectral lines?

dolimitless - 21-6-2009 at 14:21

If hydrogen has only one electron, how does it emit several spectral lines? Is it because the gradual process of it being heated? For example some electrons from several different hydrogen atoms go from first energy level to the second energy level, some go from the first straight to the third, some straight to the third?

I dont get it?

Lambda-Eyde - 21-6-2009 at 14:42

I don't get why you don't get it. The single electron can enter different stages of excitation/different levels of energy.

Although I am not a moderator nor an administrator, I'd advise you to keep these beginner questions of yours in one separate topic. It's becoming a whole lot of them.

dolimitless - 21-6-2009 at 15:46

Quote: Originally posted by Lambda-Eyde  
I don't get why you don't get it. The single electron can enter different stages of excitation/different levels of energy.

Although I am not a moderator nor an administrator, I'd advise you to keep these beginner questions of yours in one separate topic. It's becoming a whole lot of them.


What you wrote is exactly what I mentioned in my post, my answer is why? Is it because of the gradual heating of the hydrogen gas causes different levels of excitation? As you heat the hydrogen gas hotter and hotter (more kinetic energy = more collisions at gradually different energies) do the electrons enter into different levels of energy and hence different spectral (emission) lines are produced when they return to their respective ground states?

Look, I am new at chemistry. I am simply trying to learn. That's all. Please don't make it more difficult to me.

[Edited on 21-6-2009 by dolimitless]

Lambda-Eyde - 21-6-2009 at 16:05

I'm sorry if my post came out rude, it was not intentional. No harm done. :)

I'll try to explain better. Keep in mind that I am by no means an expert on this subject, however, I take great interest in this field of physics (quantum/nuclear physics).

Okay, you've got a hydrogen atom. The atom is excited by heating. Let's say there's enough energy adsorbed by the atom to make its electron jump to the next energy level and it does. After it has adsorbed the energy, the electron rapidly drops back to its ground state and emits the energy adsorbed as a red photon.

Now the atom is heated even more and it adsorbs enough energy to kick its electron even further out, to an even higher state of excitation. The electron again rapidly drops back to its ground state and again emits the energy in the form of a photon, however this time a blue one. Blue photons carry more energy than red photons.

Did that help at all? :)

[Edited on 22-6-2009 by Lambda-Eyde]

dolimitless - 21-6-2009 at 16:24

Yep, got it now, thanks :)

dolimitless - 21-6-2009 at 16:31

One more question,

I know electrons can go to a higher energy level by:

absorbing a photon
heat
and collisions with another electron

By heating a gaseos atom, isn't it going to cause more kinetic energy, thus an increase in collision? So essentially the two MAIN ways for electrons to go to a higher energy level is to:

absorb a photon
increase in heat

JohnWW - 21-6-2009 at 16:42

Quantum mechanics, in the form of the classical solution of the Schrödinger wave partial-differential equation for two bodies (one electron and proton only), by separation of variables with appropriate boundary and initial conditions, giving the Bohr equation, results in the electron of the H atom having several discrete energy levels, to which excited states it can be promoted by absorption of radiation of appropriate energy, and in which it radiates energy at discrete wavelengths on decay of those excited states. These specific wavelengths of H atoms can be used to measure the red-shift of radiation from distant galaxies, and hence their distance by means of the empirical Hubble relationship (calibrated for nearer objects by such means as parallax measurements of distance, and the absolute luminosity-period relationship of cepheid variable stars).

UnintentionalChaos - 21-6-2009 at 16:56

What JohnWW said in plain english is that the possible energy levels for electrons in a hydrogen atom are quantized. the electron cannot be anywhere, which would give it infinite variability in energy level and we'd see a continuous spectrum. We have discreet jumps and not a range. This is why you see specific lines emitted. I think the reasoning for multiple smaller jumps sometimes and larger ones other times is just tied to the probabilities of these jumps. Also, not all electrons will be in the same excitement state at the same time, so you will see a mix.



[Edited on 6-22-09 by UnintentionalChaos]

bdgackle - 25-3-2010 at 08:47

Another thing that might be confusing you is that though a sample of gas might be at a single temperature, that temperature represents the AVERAGE kinetic energy of the various hydrogen molecules floating around. The sample will actually contain molecules moving at a wide range of velocities. This in turn means that they will be colliding with each other at a wide range of velocities, allowing the various level of photon energies to be created.

A single emission event will only produce a single photon at a single frequency -- the multiple spectral lines are the product of many such events from many hydrogen atoms.