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Atomic Theory: Representing the Atom - Bohr and Rutherford

Added Oct 18, 2017 •

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there was some where you are in your studies of Science of chemistry and go today at some point you've come across the atom and what do you think about me item like this or like this or like this I think we can agree that the general structure of all of these representations is effectively the same with in the center we have a nucleus and within this nucleus the subatomic particles are the positive protons in the neutral neutrons as we move out of this nucleus we can see that it's surrounded by negative charged electrons what we want to do is to be able to communicate the number of protons neutrons and electrons because for each element in for each atom these numbers are going to be different so how do we communicate the number of pro neutrons and electrons in a particular element well there are a couple of ways regardless of the way that you're going to use you have to have a bit of information about that particular item that you're going to represent that with this level of study you're probably going to be giving this information there's something called standard nuclear notation if we think about that term nuclear refers to the information about the subatomic particles within the nucleus I typically the setup is something like this we have X representing the elemental symbol for the pic Adam that we're going to create a representation of we have two other pieces of information the atomic number and the mass number and the atomic number which is equal to the number of protons defines what an element is if there is an element anywhere in the universe with seven protons or an atomic number of 7 element is nitrogen so not only does atomic number give us the number of protons for particular element or Adam it also gives the identity for that particular element the mass numbers we can see doesn't one subatomic particle it represents the total of 2 or the total of all of the nucleons within that particular atom have you ever heard the term nucleon before really just refers to those subatomic particles that are in the nucleus the protons and the is oxygen to help us work through the construction of a Bohr Rutherford diagram and a Lewis structure for an oxygen atom as we can see here the standard nuclear notation for oxygen tells us that we have atomic number of 8 and a mass number 16 for the first step when drawing a Bohr Rutherford diagram is to draw Circle representing the nucleus and within the nucleus we have to have course indicate the total number of protons and neutrons that exist within their easiest thing to start with is atomic number because the atomic number is just equal to the number of protons that we're going to place in the nucleus in this case it's going to be 8 the mass number doesn't tell us anything about a particular subatomic particle but what it does do does allow us to determine the number of neutrons you see the mass number tells us the total number of protons and the total number of neutrons so if we know that the total number of protons as we can just subtract 8 from 16 and where the total number of neutrons not as we move outside the nucleus we have to have some way to arrange those electrons and if you remember or came up with the idea that these electrons exist in text pass orbits around the nucleus well that's since been proven inaccurate it still is valuable to know how to be able to create these Bohr Rutherford diagram the way that we go about placing these electrons is in concentric rings around the central nucleus that you may have learned there are certain numbers are maximum number of electrons that can go in these rings and that is true but I find the easiest way to construct these Bohr Rutherford diagrams is to use this that's right not only does the periodic table give us information about these elements but it also helps us construct the arrangement of electrons in things such as a Bohr Rutherford diagram so we review the periodic table quickly you'll remember that it's organized into vertical columns or groups and horizontal mr. Now the number of periods is going to correspond to the number of circles that we're going to drive around the nucleus so is you notice oxygen being in the second. Two rings around the nucleus I know what we're going to do is we're going to start counting the number of elements that are in each energy level or in each ring you'll notice in the first. There are two elements hydrogen helium goes correspond to the number of electrons that we're going to draw in that first two as we count along the second. We can see that oxygen is six elements over and that's the number of electrons that were going to drive in that second ring not we don't just place the electrons randomly on that particular nucleus what we do is we arrange them at each sort of pulled of the compass if you want to think about that until we've maxed out our first four electrons after that we start pairing them now there is justification for why that is and on to that further studies of chemistry but for now it's just good practice to put them individually until we get the first four and then we start pairing them up so as we run out of electrons you'll notice that we can count them all up and they will equal eight it is not only the number of electrons that we have here you'll notice Tulsa the number of protons that we have in the nucleus to see the elements that are on the periodic table are neutral that is the positive proton should equal the number of electrons now if this were HR particle which we refer to as an ion there would be a greater or lesser number of electrons depending on whether it was a negatively charged ion or a positively charged ion for the time being we're just going to work with neutral elements Bohr Rutherford diagram for an oxygen atom what about those Lewis structures well let's take a look at this board Rutherford diagram in a little more detail before you move on you can see that we have this outer ring in the ring is what we refer to as the valence shell contains valence electrons in its valence electrons are important because for the majority of elements they're the ones that are involved in bonding and giving that elements chemical properties of those are the ones that we're going to focus on. those are the most important ones and in fact of the Lewis structure that's what the focus is on those valence electrons so we can strip the Lewis structure the first thing that we do is take the symbol representing the element or a demand we just write it down so in the case of and it's just all done around oxygen we're going to arrange only the valence electrons in the same sort of pattern that we do with that Bohr Rutherford diagram first we put one in each one of the four poles and then we can start pairing them up and that's it now we have the Lewis structure for an oxygen atom so hopefully this video review of the structure of the atom but also in constructing Bohr Rutherford diagrams and Lewis structures for neutral atoms

Uploaded by Laura Houston.

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Atomic Theory: Representing the Atom - Bohr and Rutherford

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