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AP.Chem:

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we've learned in other videos that the atom is in fact made up of even smaller constituent particles which is pretty amazing because Adams already unimaginably small and those particles are the protons which have positive charge you have your neutrons which have neutral charge or no charge and then you have your electrons which have negative charge now the big question physicists and chemists were facing over a hundred years ago is how are these things configured and they realize that the positive charge is concentrated at the center of the atom and in fact most of the mass which is made up of the protons and the neutrons it's concentrated at the center and so the early model for how an atom worked was maybe you have your protons and neutrons in the center so let's say we're talking about a helium atom a helium atom has two protons in the nucleus and it all and a typical helium atom would have two neutrons as well so the nucleus might look something like that an early physicists and chemists said alright well look the protons have a positive charge electrons have a negative charge so they'll be attracted to each other opposite signs opposite charges attract the same charge repels each other so maybe the electron which has a negative charge orbits around the nucleus the way that a planet would orbit around its star so maybe it orbits something like this so maybe one electron has an orbit that looks something like that and then another electron if you're talking about a neutral helium atom would have two electrons and two protons well maybe the other one or bits something like this I'm trying to just draw an elliptic or a circular looking orbit and so this is the idea that the electrons are in orbits now turns out that this is not exactly the case electrons are not in these well-defined circular or elliptical orbits in fact at any given point in time it's not necessarily exactly right there it could be there but there's some probability it's here there's some probability it's there there's some probability it's there some probability it's over there and so to describe where electrons are likely to be found physicists and chemists introduced the idea of an orbital and the best way to think about orbitals is to think about a hydrogen atom and actually the math for orbitals its hydrogen is the simplest atom and so the math for orbitals has been best completed for the hydrogen atom so in the hydrogen atom especially the typical isotope of hydrogen found on earth the nucleus actually has no neutrons you just have a single proton at the center and if you have a neutral hydrogen atom that one electron instead of being in orbit around that one proton like that we can really just think about the probabilities of where it might be it could be here it could be here at any given moment it could be there at any given moment it could be off the screen at some moment but it's more likely to be in certain regions of space around the nucleus and others and we can visualize where it's most likely to be by saying all right it looks like 90% of the time it's in a sphere that looks something like that but once again it could be here it could be there could be there could be there could be there could be out here it could be anywhere we're just saying where it happens to be 90% of the time that's the visualization now an interesting question is what if you were to give that electron a little bit more energy well what does energy mean well if you think about planets or a rocket or satellite orbiting around if you were to give it a little bit more energy if you were to give it a little bit push it could have a larger orbit it would look something like that but quantum mechanics isn't about things happening gradually sometimes people think quantum means small or something like that no it really means that you're talking about discrete packets so in quantum physics quantum chemistry if you add a certain amount of energy to an electron instead of being having a 90% chance of being found in this first shell this first energy level it could then be found it would then jump into the next energy level or the next shell and so now it might be more 90 percent of the time it's going to be found in this shell right over here and then if you were to give it the right boost of energy once again just a little bit won't do you have to give it enough so that it jumps into the next energy level then it might form these weird patterns that look kind of like dumbbells where 90% of the time it's kind of you can view it as it's on the orbital that looks kind of like that dumbbell shape and you could I just did it in kind of the horizontal direction you could have in the vertical direction you could also have it on the in/out direction of this page and if you're wondering where do these shapes come from and if you keep adding more and more energy you get these more and more exotic shapes for orbitals think about standing waves that's my best hint I can give you that at the quantum level actually at all levels but especially at the quantum level you see things like electrons have both particle and wave-like properties and so imagine something like a standing wave where if I were to just take a rope and if I were to just shake it I might get standing waves that look like that if I were to take a some type of a membrane in two dimensions and if I were to push on one side right here if I were to drum on that you might get it so that this part dips down and then that part dips up and so when you get to three dimensions you end up getting this dumbbell shape when you add more energy and then you get more and more and more exotic shapes just to imagine what some of the first orbitals look like rendered by a computer you see it right over here so if you have your lowest energy electron you are in what is called an S orbital right over here and this one we would call 1s because it is at the first shell the one closest to the nucleus if you give even more energy then that electron might jump into the second energy level or the second shell and the orbital in that second shell which would be the default if it's the lowest energy in the second shell would be the 2's orbital once again you have this spherical orbital it's just a little it's more likely to be found further out than when it was just in the one shell and once again if you add even more energy you'll fall you'll still be in the second shell but you will be into one of these orbitals that have higher energies so you could view this as the 2p orbital that is in the X dimension this could be the 2p orbital that is in the Y dimension so some people call that 2px some people would call that to py this you could view as the in and out of the page so you could view that as the Z dimension so that is 2p Z and the orbitals keep going there is ad orbital once you get to the third shell once you get to the fourth shell there is an F orbital all we've talked about right now is in hydrogen if we keep giving more energy to that one electron what happens to it what is the shape of the probabilities of where it might be in three-dimensional space as you can imagine if you have two electrons it's not exactly the same but this is a pretty good approximation you can actually put two electrons in this 1s orbital but after that you could imagine the electrons are repelling each other so another electron doesn't want to go there and so then the third electron that you add is going to end up in the 2's orbital it's going to be at that higher energy level and then that can fit too so you can fit up to 4 electrons between the 1s and then the 2s and then the fifth one it's going to have to go into one of these P orbitals now one last point is to make sure you understand the terminology of orbitals and shells so first of all you have this idea of shells and sometimes the word shell will be used interchangeably with energy level energy levels and so in this diagram or this visualization right over here I've depicted the one shell and then I've also depicted the two shell so this is a shell right over here this is another shell now you'll also hear the term sub shell sub shell or sometimes people will say sub levels and that's where they're talking about s or P or D and eventually F so if I circle this I'm talking about that first shell now the first shell only contains one subshell and that's the one s subshell and the one s subshell only has one orbital once again the 1s orbital so for the first shell the shell the sub shell in the orbital is all referring to the same thing but as we get to the second shell it's a little bit different if we talk about the sub shells the in the second shell there's s n P so this is a sub shell and then this is a another sub shell right over here there's actually three orbitals in the P sub shell so I'll leave you there in the next video we'll actually look at various atoms and think about their electron configurations where do their electron sit in which of these shells sub shells and orbitals

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