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Atomic Theory: The Bohr Atom - Bozeman Science

Added Oct 16, 2017 •

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it's mr. Anderson in this is AP Physics essential video for it's on the atom in the last video we talked about how Ernest Rutherford and his gold foil experiment help scientists discover this positive small nucleus in the center of an atom but that didn't tell us what the electrons were doing and he just speculated that they were moving around the nucleus almost like planets in orbit around the Sun but what other pictures working underneath Rutherford Niels Bohr spotted a problem in this any charged particle that's moving is going to be giving off electromagnetic radiation as it does that it's losing some of that energy and so it's going to quickly spiraling metal in denial 8 essentially the whole Adam so he knew that wasn't right he also knew as it gives off radiation and as it varies we're going to get this nice smooth Spectrum Spectrum electromagnetic radiation given off by high-energy atoms but when we started to look into space what we found is that light wasn't smooth it had these discrete units within it and so that Spectra had described and Bohr's model helped so if you think of it like this and this works for hydrogen is what the Bohr Matt Bohr model is built on you have these energy levels into an electron can be in energy level one energy level to energy level 3 but it can never be found in the quantized it has to be in one of those levels or another level and so what how does it move between levels well if it absorbs energy from a photon electromagnetic radiation for example it'll jump to a higher level and as it moves it's going to admit those photons and that help to describe what was it what we were seen in the Spectra and said that improved our model so we have now had the cloud that had the electrons in it and then the nucleus and so we found these negative electrons in the cloud and then protons and neutrons were found in the nucleus and in a neutral atom the number of protons and electrons are going to be equal in the electrons tell us a lot about the properties of that atom in fact the whole periodic table is built on the electrons electrons especially we have these outer levels now the Bohr model helps us explain what those electrons are doing and how they're moving they move into these discrete energy states and that helps us to explain the Spectra and so if you look at any kind of an atom on the periodic call the atomic number to tell us the number of protons we have so we're going to have these positive protons that are going to be found in the nucleus we can kind of figure out how many neutrons roughly we're going to have in an average atom by taking the mass number subtracting you number until we would knowing helium for example that we're going to have two neutrons now since the number of protons and electrons are the same in a neutral atom we can figure out that we've got these electrons moving around the outside and the number of electrons that we have out there tell us a lot about the properties of the atom is if you look at the periodic table this whole thing is essentially built on the number of electrons that we have because that tells us a lot about the properties and so if you look right here we'll find copper silver and gold which are all very similar are in the and that essentially says that they have similar outer level electrons are free look in the First Column all of these are highly reactive all the noble gases are not into the properties of atoms are built on those electrons but there were problems with this play remodel electrons were orbiting like a planets they were actually jumping between orbits according to Niels Bohr and so they didn't just move back and forth on all these infinite number of orbits around the nucleus giving office do the amount of spectrum almost like a ladder than an electron could be here but it could also be here and it can never be found in the middle we call that being quantized it has to be in a specific unit to exist the how do you move an electron to a farther level while you have to put a little bit of energy into it so we had a lot of energy we could jump it up up to this energy level and as it falls back down it's going to release a certain amount of energy and said this is a visual or a model of what the Bohr model might look like orbits around the center if it receives a photon it jumps to a higher level if it gives off and equal Photon it will drop down to a lower level and so it's only existing and he's quantized or Miss how to explain Spectre because before I was discovered or or was put forth people in started discovering Spectra they were looking into space not with just a prison but a spectroscope so there was splitting the light into all of its different wavelengths and they were start see these lines when you're looking at the sun for example which is mostly hydrogen we saw these different series of the Lyman series was developed by one scientist he was using spectroscopy and he came up with a equation that explain what was the John but you can see this Spectra because it was into ultraviolet are we also that saw the passion series that was showing a similar relationship but this was in the infrared and the Balmer series was he in the same thing so what really he was explaining what's the road summer series up here is that they were seen these discrete units of light and so where was that light coming from a look at hydrogen but you can see here as we move from this energy level 202 energy level 3 there's a certain amount of energy in as the electron falls back down it's going to give off that energy it's going to give off that light and so the Bohr model predicted what these numbers were and they fit perfectly with the numbers that we were seen in the Spectra so again this only works for hydrogen and so it's a good step model or it's a good model to get you started on a understanding how the atom is really put together but did you learn the energy level structure of an electron in an atom at the appropriate scale being and in this case is that these energy levels in hydrogen atom I hope so that's the Bohr model and I hope that was helpful

Uploaded by Laura Houston.

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