now that we've discussed some of the historical atomic theory or how we know more about the atom and some of the discoveries that were found we need to go ahead and apply what do we now know how can we construct an atom we know that the atom itself is composed of protons neutrons and electrons the protons and neutrons present in your nucleus the electrons are outside of your nucleus in specific orbitals or specific energy levels so for protons neutrons and electrons we do have abbreviations we use because we're not going to write out these words all the time protons abbreviations include a lowercase p a lowercase p with a plus sign that's most often what i will write when i mean just a purely proton in the sense of atomic structure the positive just showing me the charge on a proton and h plus we'll use h plus as a proton a lot throughout general chemistry and we'll see it kind of play through um all the first semester and we'll apply it a lot in second semester but basically if you look at one hydrogen atom one hydrogen atom has one proton in its nucleus it can have some neutrons it can have anywhere from one to three neutrons depending on which isotope it is we'll talk about isotopes just a bit but it also has one electron if that hydrogen atom loses that one electron all that's left is the proton in the nucleus so h plus a hydrogen atom with a positive charge has lost that electron all that's left is a proton so we call this a proton because it's all again that's all that's left it's lost it's one electron the mass of a proton in kilograms we do report this in kilograms because kilograms is the s i base unit for mass so the mass of a proton is 1.67272 times 10 to the 27 kilograms and no you do not need to have that number memorized if you need that value we will give it to you you do however need to know that the mass of a proton is approximately one amu amu stands for atomic mass unit the charge on a proton is positive 1.602 times 10 to the negative 19th coulombs coulomb because that is our si unit um i si base unit for charge is coulombs you don't need to know that value if you need it i will give it to you you do however need to know that a proton has a plus one charge there's not a unit on that we're on where i say plus one it proton it has a plus one that's what you need to know neutrons neutrons are completely neutral a neutron abbreviation we can write a lowercase n i don't usually write a lowercase n just because lowercase n also represents uh moles which we'll talk about in just a bit the other abbreviation you'll see is n with a zero zero meaning zero charge the mass of a proton is actually a little bit bigger than um or sorry the mass of a neutron mass of neutron is a little bit bigger than a proton it's 1.7 1.67 times 10 to the 27th kilograms and no you do not need to have that number memorized you do need to know that the mass of a neutron is approximately 1 amu so we say that the mass of a proton and the mass of the neutron are basically the same they're not truly the same but we treat them as being the same the charge is completely neutral meaning it has no overall charge and electrons the abbreviation for electron is a lower case e with a minus sign minus because electrons have a negative one charge the mass of an electron is 9.10939 times 10 uh these should be minus i apologize for that there should be negative signs in front of they're very small numbers minus 31 kilograms so please make sure you realize where i wrote 10 to the 27 that should be 10 to the negative 27 kilograms for both protons and neutrons and it is 10 to the minus 31 kilograms for an electron it's kind of a um it's a weird number but what you need to get out of this what's important here is an electron is approximately 1 2 000 amuse so it's about 2 000 times smaller than a proton or a neutron the charge on an electron is opposite in sine but the same magnitude as the proton so 1.602 times negative 10 to the negative 19th coulombs but it has a negative sign out in front so it is a negative charge and overall we write this as negative one so you can think of a neutron in this way a neutron is sort of like a proton plus an electron this is a gross oversimplification um we will see this actually come back in second semester when we cover nuclear chemistry and we'll get more into it at that point what you really need to know about neutrons right now we're going to talk about with isotopes and such neutrons reside in your nucleus different atoms can have a different number of neutrons even within the same element that's what creates an isotope again we will define that when we touch on isotopes but in mass and charge a proton plus an electron is pretty much a neutron so in charge proton plus electron gives me a neutral compound in mass the mass of a proton that is a negative 27 up here plus the mass of an electron basically a proton we're also again when we cover nuclear chemistry at the um in during gen chem 2. we're going to talk about nuclear decay a lot there's a number of elements whose atoms are not stable so they undergo radioactive decay which we study in nuclear chemistry and so we can have beta decay or electron capture in a bit in beta decay a neutron we have too many neutrons in your nucleus and we're going to show you guys how to figure that out but again that is the second semester concept but in beta decay you've got a neutron breaking down into a proton and ejecting an electron electron capture occurs when we have too many protons in our nucleus so a proton will actually capture one of its own electrons and form a neutron and it just brings out about a more stabilization of the nucleus you're not responsible for these things yet what you are responsible for is understanding this table understanding their abbreviations their mass and amu and their charge okay so you and you need to remember protons and neutrons are in your nucleus electrons are not they're in orbitals outside of your nucleus you also need to understand that the protons the number of protons in a nucleus is what defines what element i have if i change the number of protons in a nucleus that is number one undergoing nuclear chemistry but number two that changes the identity of the element i can change the number of neutrons and the number of electrons that does not change the identity of the element but if you change the number of protons that does change the identity of the element you're discussing so some terms we need to cover atom ion cation and anion um so adam when we use this term atom us specifically saying the word atom is emphasizing the fact that that specific particle is neutral in charge so an atom has a neutral charge what i mean there is that the number of protons in the atom is equal to the number of electrons so they completely cancel each other out it is what we call electrically neutral meaning there's no overall positive or overall negative charge to the um to the compound or to the atom itself so whatever atom you're looking at there's no overall charge an ion is any charged particle when i say charged particle i just mean that the number of protons you have does not equal the number of electrons now i'm not specifying which way it's going i'm just saying an ion is charged and in an ion the number of protons and the number of electrons are not equal to each other so we will either have a positively charged ion or a negatively charged ion of course those words are kind of bulky to say so we say cation for positively charged ions cation is a lot faster to say than possibly charged ion you need to know that cation means positively charged in order to have a positively charged ion the number of protons you have must be greater than the number of electrons the flip side of that is an anion an anion is a negatively charged ion and in an anion the number of protons is less than the number of electrons so when we're forming ions ions form very regularly in chemistry we're going to do this a lot when we form ions we are only gaining or losing electrons we are never gaining or losing protons so in a cation that atom that neutral atom lost electrons to form a cation so you've got a neutral atom it lost electrons and formed a cation in an anion you have a neutral atom that gained electrons and forms an anion so down here in the picture we see a sodium atom and a sodium ion and if you look here we have in our nucleus 11 protons and 12 neutrons in both species but in a sodium atom we also have 11 electrons the number of electrons must equal the number of protons note the number of neutrons does not have to match anything the number of neutrons can be different there's specific numbers of neutrons that these atoms will have depending on the atom itself but the number of protons and electrons must match if it is a atom meaning it is a neutral species but when we form a sodium ion this is specifically a cation because it is a positively charged species we see that we have 10 electrons to 11 protons we have lost an electron 11 protons to 10 electrons it will have a positive one charge we also it's kind of hard to see we but we also see that size wise the cation is actually a little bit smaller and that is actually correct we have the same number of protons but one less electron so the atom itself when it when the atom loses an electron and forms that ion it actually gets a little bit smaller in size okay a lot of these terms we use interchangeably and not always correctly so i want to be very clear on what these terms actually mean so we've got compounds mixtures elements atoms and molecules what's going on atoms themselves are individual elements so when i say atoms here this is an atom and this here just has one element listed so this first box here in green the green little dots mean i have one atoms of one specific species in here we could say these are all zinc atoms zinc is one of our transition metals we could say they're all sodium atoms sodium is one of our alkaline earth metals or sodium is one of our alkali alkali metals um we could say barium they're all barry maps barium is one of our alkaline earth either way they're all individual atoms of a species and this box here is an individual element so we do not have a mixture going on here what throws students off is that even if we have just an individual element here we could have atoms or molecules there are a handful of elements on the table that don't want to exist as a single atom for energetic reasons they form a multiplet of themselves or a molecule so we're going to learn about our seven diatomics and then there's um four or five other elements that also form kind of a multi-atom species for better stability of itself so for example o2 is what we call oxygen this is what we breathe in me and you that's how we survive we breathe in oxygen but oxygen isn't just a single oxygen atom it's actually what we call an oxygen molecule because it's two oxygen atoms bonded together this is what we are breathing in this is what exists around us oxygen is more stable energetically when it forms a molecule so it does that in its natural state does that mean that i can't have just a single oxygen in a reaction no i can but if i say oxygen and we're going to talk about this again in chapter three when they're naming but if i say uh something's reacting with oxygen i actually mean molecular oxygen or also known as diatomic oxygen dye meaning two so an individual element can exist as atoms or molecules depending on what species you have most elements do exist as atoms but again there are seven diatomics and then four or five other elements that exist as a multi-atomic species a mixture is when you have two different things mixed together we can have a mixture of atoms so this box here of orange and green this is a mixture of two different atoms it's just putting two different things together mixing them up it is a mixture it's not one individual species but it's a mixture of individual atoms so two different elements next box over we have a mixture of atoms with molecules here we see atoms and molecules mixed up together so again this would be like if i had oxygen mixed up with an element that otherwise exists as just an individual element like maybe oxygen with neon gas this could be oxygen molecules and neon atoms floating around we can also have a mixture of molecules of an element so such as oxygen and nitrogen mixed up together and we can have molecules and a compound mixed together compound or m these here means um we call these both molecules and compounds we call them molecules when they are molecular compounds we'll talk about molecular more in chapter three but a molecular compound is something that's comprised of non-metals and so most often represented here would be like water water is a water molecule water exists as an oxygen atom bonded to two hydrogen atoms in this case i could have say water and oxygen mixed together i could if you think about air the air around you air is i believe it's like 68 nitrogen which is n2 we've got the oxygen we breathe it also has carbon dioxide in it because we breathe it out and it's got other smaller amounts of um gases in it but this is a large component of the air around us a large portion of its nitrogen and then from the remainder a large portion of that is oxygen a large portion is co2 or carbon dioxide this mixture would be like this where i have a mixture of molecules and molecular compounds and lastly the compound itself here we see molecules of a compound and again that means that i have different atoms bonded together so like water carbon dioxide carbon monoxide nitrogen dioxide we're going to talk more about ionic compounds in a little bit they're actually formula units but we call these compounds as well like sodium chloride which is table salt those are when you're mixing up multiple elements into one compound a lot of times you're going to find just two elements but that doesn't mean it can only have two we have many species or many different um products um compounds out there that have more than just two elements but i want you comfortable with these terms so please read through this and make sure you're comfortable using these terms and in your mind you can picture what an atom is or what a molecule is what a mixture of atoms is a mixture of molecules and atoms a mixture of molecules a mixture of molecules with compounds and a mixture and then just compounds in general can you picture this in your mind and the better you can picture it the easier this this course will go because you need to be able to picture what's really happening so atomic structure we do have a modern view of the atomic structure um we know that the protons and neutrons reside in our nucleus and we know that the electrons exist we have a probability of finding an electron in a specific space outside of our nucleus this um the drawings here are kind of an extension of the bohr model and it's the easiest way for us to kind of define it and show it even though we know that the electron does not have to reside in the exact same exact spot that we're drawing it but here is again here's a hydrogen atom we have one proton in our nucleus and one electron so this is showing again our proton in our nucleus here that will contain our positive charge and any neutrons we have and then the electron is orbiting outside the second drawing we have here i know that this is a helium atom how do i know this is helium i have two protons two protons means that this element has an atomic number of two atomic number of two is helium helium has two protons in its nucleus i'm also showing two neutrons here we can have a varying number of neutrons but outside of that is where we get the electrons so again uh mass the denseness of your atom is in its nucleus the bulk of the mass is in the nucleus the electrons take up very little mass and float in the or move around in the orbitals or the electron clouds outside of the nucleus surrounding the nucleus okay so again we i know i've said this but just reiterating it please write the sounding notes you have i want you to envision this in your mind the volume of an atom is determined by the electrons and is mostly empty space most of the mass of an atom however lies in the nucleus which is extremely dense so the nucleus itself is containing your protons and your neutrons but the volume is determined by those electrons where are those electrons moving they may not weigh very much but they're moving and they're moving fast depending on how much energy the compound has if they're in the solid phase they have less energy than in the liquid phase than in the gas phase etc but where are the electrons moving that determines the volume of your atom you need to know these following terms as well atomic number atomic number we write this as the letter um capital z and atomic number tells you your number of protons you can find the atomic number on the periodic table we'll cover this again in the section on the pr table but if you look at the periodic table say we look up hydrogen at minimum you will find the following information on the periodic table at minimum it will say this this elemental symbol tells me it's hydrogen the one up here is your atomic number the atomic number tells me the number of protons that that atom has it also tells me the number of electrons if it is actually an atom and not an ion because the number of protons and electrons must match and this number down here is what we call your mass number or um your mass member atomic mass we're going to call it atomic mass because mass number is slightly different we call it your um i keep writing the wrong word i'm sorry atomic mass is what i'm trying to write and we're going to use atomic masses to figure out molar masses in a different sec part of this um chapter but atomic number is that number on top and it tells you the number of protons and number of electrons for an actual atom number of protons no matter what number of electrons if you have an atom so neutral species butter in the middle elemental symbol and the number at the bottom is your atomic mass for that specific element your mass number which is what i was trying to think about a minute ago your mass number is actually equal to the number of protons plus the number of neutrons because this is what's going to control the mass of your atom itself and then we also have isotopes isotopes are atoms of the exact same element meaning they have the same z value but they differ by the number of neutrons so pictured here i show you protein deuterium and tritium these are the three stable isotopes of hydrogen hydrogen no matter what has one protein okay so again hydrogen three naturally occurring isotopes protium deuterium and tritium this blue dot in the middle here is your proton we see that protium has one proton and one electron all of them have one electron as well because they're all hydrogen atoms and they'll have one proton and one electron it's neutrally charged but protium only has a proton in its nucleus it has zero neutrons deuterium has one proton and one neutron and tritium has one proton and two neutrons these are all atoms of hydrogen but they're different atoms they have a different mass and so we can do some really cool chemistry with this stuff we need to understand what an isotope is it's the same element the only difference is the number of neutrons in your nucleus so the way we write this out we write out your elemental symbol e it's your whatever element of something you're looking at we write your z value down here z again atomic number it is slightly redundant to have it there but that's where we write it a your mass number and if needed the charge so z down here is your atomic number a up here mass member which is your number of protons plus your number of electrons and charge if the species is an ion it will have either a positive or negative charge and we specify that charge by writing it there if it doesn't have a charge so it's a neutral atom we do not write anything we just leave it blank we're going to show examples in the very next slide but i know they're written down here for hydrogen here um for the different hydrogen ions let's go ahead and write them ourselves so for protium we're gonna write our elemental symbol h for hydrogen hydrogen has an atomic number of one because it has one proton we see that there's no neutrons here so one proton plus zero neutrons gives me a mass number of one deuterium it's also an atom of hydrogen which means it has a one for its atomic number but deuterium has one proton and one neutron which means a mass number of two and tritium also an isotope of hydrogen it is a hydrogen atom it's just a specific hydrogen atom with a specific name atomic number is one and its mass number will be three so let's go ahead and just use all of our recently found knowledge and fill in the following table here we're looking we're giving you a partial symbol why do i say partial because i haven't listed your atomic number on these i've just told you which isotope it is you the rest of this information you can fill out so i want you to tell me your atomic numbers here and the number of protons neutrons and electrons for each species so first let's look at carbon the way i say this the way i pronounce this i say carbon 12. you can write this one of three ways you can write carbon 12 you can write c12 or what you will see most often is written like this all of them mean carbon 12 which is telling me it's the carbon-12 isotope when i find carbon on the table i see it has an atomic number of six since these are all carbon i'm just going to write all of them down right now i want to know the number of protons the number of protons is determined that's what determines what element you have the number of protons equals your atomic number so because these are all carbon these all automatically have six protons next i'm going to look at the number of new or number of electrons i'm going to skip neutrons per second which electrons why because these are all neutral atoms and so i know because they're neutral that my number of protons must equal my number of electrons how do i know they're neutral because there's nothing written up here on these two there's something written up there but since i have nothing written there i know these are neutral atoms therefore there are six electrons in each one lastly let's look at the number of neutrons i know my mass number is equal to the number of neutrons plus the number of protons for carbon 12 my mass number is 12. that means my number of neutrons plus my number of protons equals 12. i have six protons each proton contributes one which means overall i have 6 neutrons for carbon 13 i will have 7 neutrons and for carbon 14 i will have 8 neutrons carbon 12 is the most abundant carbon isotope there is if you have a hundred atoms of carbon 99 of them will be carbon 12. one of them will be carbon 13. some students will say okay but you just told me that there's an ice cream carbon-14 yeah there is it exists in a very small amount uh carbon 14 you're going to learn more about when you learn about nuclear chemistry but it's actually created in our upper atmosphere through a radioactive reaction of nitrogen being converted into carbon that carbon then reacts with oxygen to form co2 which comes down to earth is absorbed by our plants and moves its way up its food chain if you've ever heard the term carbon dating we use carbon dating to determine how old something is and carbon dating is um they do this by analyzing how much of this carbon do we have present so how much carbon 14 do we have they can actually measure that and it's kind of cool the chemistry they do they can measure the ratio of carbon 14 we have in species and estimate how old it is so of course once the species passes away it stops incorporating more carbon-14 into itself because well it's no longer eating things uh so mean you have carbon-14 mess small amounts don't do anything it's not bad people get really kind of freaked out when they hear radioactivity or radio nuclear decay you're fine but i just think it's kind of cool how we can actually estimate how old something is carbon 14 um data or carbon dating is accurate to about 50 000 years due to the half-life of carbon 14. back to the table um sodium 23 if i look up sodium on the table sodium is a group 1 metal an alkali metal it has an atomic number of 11. i see i have a plus one charge here how do i know it's plus one because if you just see a plus sign it means plus one if you just see a minus sign it means minus one we don't write the number if it's a one but number of protons i know my number of protons has to equal my atomic number so i know i must have 11 protons because i have a positive ion i have a cat ion that means i have more protons than electrons and in this case it's more by one 10 electrons plus 11 protons will give me a plus one charge lastly our number of neutrons we've got our mass number number of protons plus number of neutrons equals 23 we have 11 protons therefore we must have 12 neutrons and phosphorus 31 ion it's the p3 minus and it's phosphorus 31. go ahead and find phosphorus on the table it is one of your nonmetals you should find its atomic number to be 15. that means my number of protons is 15. i see now i've got a 3 minus charge a negative ion is called an anion anion means that the number of protons i have is less than the number of electrons i have i have more electrons than protons in order to cause a negative 3 charge that means a phosphorus atom has gained three electrons because again we can only gain and lose electrons in sodium to form sodium ion that atom lost one electron to form the phosphorus ion here it gained three electrons and lastly my mass number here is 31. so 15 plus what equals 31 15 plus 16 equals 31. so you should be able to if given anything like this you should be able to tell me the number of protons neutrons and electrons the charge on the species say i told you say i wrote this stone it asked you for number of protons neutrons of electrons and i asked you what this is called you should tell me it's an oxygen 18 ion specifically an anion that's negatively charged has a two negative charge oxygen likes to be too negative it's preferred way to be if it's going to have a charge at all and you should tell me the number of protons neutrons and electrons for that species okay you