hi everyone welcome again to biology 231 human biology one biology is the study of life and we're going to focus on humans naturally but keep in mind that we're just a small part of all the life out there so when we talk about these levels of biological organization in this image keep in mind that this applies to many other forms of life too now there are simpler forms of life for example bacteria they are only single cells and so they're not going to have these higher levels of organization that you see here in the bottom portions of this image but other forms of complex life for example other mammals for instance so where humans are in the mammal category so other mammals for instance will have these levels of biological organization that we're going to be discussing but naturally we're going to focus on the structure and function of the human body we're going to start off with atoms and atomic structure so we're going to talk about a little bit of basic chemistry so this is the chemical level which i have boxed in on this slide of life and then we're going to use that to build to our understanding to the higher levels of biological organization now students have a tendency to get a little intimidated with chemistry i'm here to say don't worry right we're just going to do some basic chemistry that's going to allow you to understand some of the biological processes a bit better later on in the semester okay so we're not going to spend a long long time on chemistry but there will be some chemistry in this first unit but that's book that is going to make you more easily able to understand again some of the processes we're going to talk about soon so what i want to start out with is defining these different levels of biological organization remember my suggestion is to you can always pause right and then go back and play the video multiple times but try to answer the study guide questions as you go along so when you look at the study guide for exam one there'll be an atoms and atomic structure section so in other words the major points you're supposed to get from this set of slides so you can listen to the video once through and then go back and answer those questions where you can work on it gradually you just have to figure out what's best for you okay how you learn the best but remember you do want to answer those study guide questions okay so you're going to see what are the levels of biological organization give me some examples and define those levels so that's what i'm going to take you through right here on this image so it'll be a little bit of a preview of where we're headed to after chemistry so we're going to get into atoms and molecules in more detail in this set of slides in the next set of slides but just briefly atoms are part of matter okay and we're going to get into matter here in a little bit too but atoms are part of living and non-living things and most atoms are not stable they interact to get stable and when they interact they form this next level called molecules keep in mind we're still in the chemical level of biological organization so atoms are interacting to form molecules because they're going to get stable that way in other words when atoms interact that's called being a part of a chemical reaction okay so molecules can also interact with one another and then we're going to get this next level okay so we're going to hang out in this zone the chemical level for this first unit okay in this class and then we're going to move on but just to give you a little preview and understand again the big picture let's define these other levels okay so when molecules interact in us they can form organelles okay now an organelle again don't get this confused with organ that's a higher level here an organelle is a small structure within the trillions of cells within our body okay and these little structures within a cell like a muscle cell or a skin cell a stomach cell these organelles allow the cell to stay alive they perform a number of functions and we're actually going to get into those functions in the next unit when we get into the cellular level of organization so organelles are structures within cells that perform various functions now let's do some examples here because i i skipped over that you're going to list some examples of these different levels of organization while you fill out the study guide so atoms atoms like carbon or hydrogen or oxygen those are the types of atoms that interact to form molecules what's a good example of a molecule well water h2o water a water molecule is made up of two hydrogens and an oxygen that's why it's called h2o okay and we're going to talk about kind of the how you write out molecules okay you're going to actually be working on that in lecture and lab so you'll get used to that but for now an example of a molecule is water a fairly simple molecule but very important a bigger a much larger molecule that's important in us would be dna deoxyribonucleic acid so your dna or your genes have the codes that you actually pass down right but also those codes tell your cells to do some important things like make proteins so atoms like carbon hydrogen oxygen they interact to form molecules water dna to name just a couple and molecules interact to form these small structures within a cell called organelles now you may have heard of these before if you remember way back taking kind of one of your first biology classes maybe in middle school or high school that these organelles there's quite a few but the nucleus of a cell the majority of cells in your body has a nucleus that's where the dna is actually located um but there's other organelles they have there's mitochondria that make the energy called atp to really fuel your cells activities so there's going to be many more organelle examples that we go through but for now a nucleus mitochondria you can read about some more examples in your textbook organelles form cells okay now the cell is actually kind of a special level of biological organization because this is as small as you can go and still be considered living so cells are alive they have all the characteristics of life for example they respond to stimuli they reproduce themselves so all of life's characteristics below that it's considered non-living so organelles molecules atoms this chemical level we're going to start out with okay non-living okay but those non-living well excuse me those non-living levels make up the living level the cellular level and the human body like i said has trillions of cells okay many varieties and those cells share some common characteristics but they also have some differences and we're going to get into that in the next unit so cells is the smallest living unit of life okay the next level is the tissue level now remember was going one notch higher a tissue like this example smooth muscle tissue that happens to for example push food along in your intestines or in your stomach smooth muscle tissue a tissue is just a group of cells that have the same structure and function so smooth muscle tissue is made up of smooth muscle cells okay there's nervous tissue nervous tissue is made up of nervous cells okay so we're just going one notch higher in the level of organization so tissues a tissue is a group of cells and you're going to learn about in the lab portion of the class you're going to learn about the different tissues in us a organ now organ is kind of common language right organ you've heard of so stomach heart brain spinal cord and organ is the next level of organization and organ is made up of two or more different tissues so look at this example a blood vessel is made up of a tissue type called connective tissue that's supportive it's made up of muscle tissue to help control blood flow for example when this muscle tissue squeezes it will decrease the diameter okay the width of that blood vessel and slow down blood flow or that muscle can relax and open up those that blood vessel to increase blood flow so there's also epithelial tissue lining this blood vessel so those are actually three different tissue types so a organ is a structure made up of two or more tissues okay and let's see the next level is the organ system level now this is you've heard of this level excuse me you've heard of before too the cardiovascular system the nervous system the digestive system there's actually 11 organ systems in us you're going to be starting to learn about some of those organ systems like the skeletal system in this course but an organ system is a group of organs that are contributing to a common function for example the cardiovascular system in this image is made up of your heart blood vessels and actually blood too blood is the transport transport substance like oxygen nutrients your blood vessels are the highways for blood to travel and the heart is the pump okay so those organs interact to form the cardiovascular system which overall makes sure that you have important stuff delivered to your cells and also waste get taken away so the nervous system is a communication system organs within the nervous system the brain spinal cord nerves make sure that you have that quick communication to really keep your body functioning so reproductive system like i said digestive system urinary system there's lots of examples and then us the organismal level okay a human is made up of multiple specifically 11 organ systems okay so i just want to give you a little preview of where we're headed we're going to talk about a couple of organ systems in this course and then when you continue to human biology 2 biology 232 you're going to be talking about the rest of them in more detail so we're going to start with this chemical level and we're going to do some definitions and then look at atomic structure so let's go ahead the next slide here matter i mentioned before now matter is anything that has mass and takes up space so matter is actually part of living things and non-living things right your table is made up of matter okay your body is also made up of matter and there's various states of matter okay phases they're called solid liquid liquid and gas which you've heard of i'm not going to get strict for you to know these characteristics over here so the characteristic differences between solids liquids and gases we're going to talk about many examples of each phase type as we go along in the semester so you'll get a better idea of them but these are the three states or phases of matter and they have some different properties what we're going to focus on is what matter is composed of matter is composed of elements okay you might have heard of the periodic table of elements before we're going to talk a little bit about that as we talk about biological processes but matter again whether it's part of a non-living thing like your table or you is made up of elements and these elements cannot be broken down by typical physical means okay and different elements have different properties and as you can see on this periodic table the color coding here these different elements have a symbol and we're going to talk about that a little bit too but they also have some different properties and the colors so atoms or elements that are in a particular color like this orange color blue yellow gray green they're actually grouped in this table based on common characteristics okay so an example of a characteristic would be different boiling points okay different freezing points okay for example or whether they're solid let's go back to this whether those elements are solid liquid or gas at room temperature okay so their properties differ now how are they symbolized well they have a one or two little letter excuse me chemical shorthand so for instance where's carbon right here carbon okay is actually abbreviated by its first letter c okay so that's the carbon symbol oxygen is abbreviated by its symbol it's first letter symbol i should say oxygen okay that o and then we have some that have two let's find let's see lithium here li okay that's a good example of two sodium that's part of table salt for example it's abbreviated n a okay so again this is not a chemistry class so you're not going to have to know all of these elements again that's for chemistry and learning their properties we're just going to talk about the elements that are primarily um making up the structure of us okay so that we're going to talk about essential elements so let's move on to this so there are actually 92 naturally occurring elements 25 are essential to us okay now again you're not going to have to know those 25 you can certainly read up on those if you're curious but i want you to know the big four in other words which four elements make up the most of us so again which four make up 96 of us and other living things as a matter of fact so take a look here what i boxed oxygen carbon hydrogen and nitrogen those are the big four and they are abbreviated by their first letter so o for oxygen c for carbon h for hydrogen and n for nitrogen and you can see their percentage here you don't have to know their exact percentages but these four add up to 96 percent okay oxygen as you may know is delivered to our cells constantly so that they can make energy for all their needs and we're going to get into that in a few weeks okay during our second unit so this is what i want you to know i want you to know that these four that i have boxed make up 96 of us and other living things too but just in a different percentage this is the human percentages here and i also want you to know their symbol so you only have to know these four symbols n for nitrogen h for hydrogen c for carbon and o for oxygen the other thing i want you to know i'm going to point out here with this image trace elements now you're going to see lesser elements talked about in your textbook and on this table here okay so these just mean important elements that are needed in a lesser right amount okay a lower concentration in other words you can check these out right some of these should make sense we have potassium sulfur magnesium but i'm going to go down here to the trace elements okay i want you to know an example of a trace element and what a trace element is so these are needed by your body but just in a very small quantity so a very low concentration so they're still very important but they're needed in very small amounts so for example here iodine which has the symbol i okay iodine is needed by for example your thyroid gland to make some hormones that are important for metabolism so controlling your chemical reactions in all your cells so just one example okay also i want to point out that iron here fe is the abbreviation see how low a concentration this is here compared to these other lesser elements iron is usually considered a trace element too and so you can know iron as an example of a trace element that's fine with me iron actually is in cells in your blood called red blood cells it helps you carry the oxygen around that your cells need okay so just one example of a trace element so any of these here and you can even use iron as a trace element very important but needed in a small amount in our body and of course make sure you know those big four those top four now we're going to head into atomic structure so more about atoms okay i mentioned them briefly at the beginning so elements again let's go back to the slide elements cannot be broken down by ordinary physical means so elements are part of matter and an element has these structures called atoms within them okay so the atoms of different elements so the carbon element for example is made up of carbon atoms the oxygen element is made up of oxygen atoms etc so we're going to learn about the structure of these atoms and that's going to help you again understand some biological processes that we're going to discuss so atoms of different elements differ by these smaller particles within them called subatomic particles you may remember these from an earlier chemistry class if you ever had a little bit of chemistry before but we're going to go through these so protons neutrons and electrons these are a few of the subatomic particles that are parts of atoms there's also many others but these are going to be relevant to our discussion so the oxygen atom for instance has a certain number of protons neutrons and electrons if you go to a different element it's going to have a different lineup nitrogen has a different amount of protons neutrons electrons so we're going to talk about the location of these and diagram it a little bit and where we're headed we're going to talk about what about these atoms structure is going to determine whether they interact in other words participate in chemical reactions that's where we're headed so let's take a look at these okay some of some examples here so these three first they have different charges on them protons think p for positive protons have a positive charge neutrons think neutral neutrons have no charge another subatomic particle that's important within an atom electrons they have a negative charge okay so different charges now let's look at these diagrams atoms are diagrammed in different ways but look at the location of these that's consistent these first two protons and neutrons of an atom they're always located in the center of an atom so these would be protons and neutrons these would be protons and neutrons these two imagers are actually both of the atom or element helium here's helium he okay so we're gonna start with practicing diagramming with helium so again the color codes do not matter okay but protons or neutrons are located in the center of an atom that center is called the nucleus and it's a little confusing because the nucleus is actually an organelle a higher level of organization in cells so just because these subatomic particles protons and neutrons are found in the center of an atom the nucleus is relatively in a center of a cell so that's why they use that same terminology but the nucleus of an atom is not the same as the nucleus of a cell that's a much higher level of organization that we're going to talk about later so neutrons and protons in the center of an atom and we're going to talk about how to figure out the numbers within an atom of these subatomic particles let's start with the location protons and neutrons in the center here now this picture down here either even has a little positive that's how you know that these this red is using that to symbolize the protons but it doesn't have to in the picture but protons and neutrons are in the center electrons are actually floating around in what's called energy shells outside the nucleus so you see this ring here here are a couple of electrons helium actually has two electrons so you see two here electrons are very very very small compared to protons and neutrons okay so much so that electrons do not significantly contribute to the weight of an atom because they're so small in this picture they have the charges so we know these are electrons one because they're outside the nucleus they're in an energy shell but also because they have the negative charge and that's what electrons have on them so take a look at this helium atom it has two positive charges two protons and then two negative charges in the way of electrons see they cancel each other out okay so overall this helium atom is considered neutral okay and most atoms that we're going to start out with here are going to be that way the positives cancel out the negatives okay now let's look at these again electrons in the shell okay this cloud out here same down here so again focus on the location not the different color codes okay you do not have to when you're putting diagrams or i'm sorry when you're diagramming these you don't have to include the charges okay but you can just put electrons as dots okay outside the nucleus so how do we determine how many protons neutrons and electrons are in an atom well that's where we're headed next and we're going to do lots of examples of this so atomic number whenever you see an atom you see it's symbol right again you don't have to know any other symbols but the big four right carbon hydrogen oxygen and nitrogen so you'll be given an image just like this without these labels okay this happens to be helium and there's two numbers associated with it if you look closely at the periodic table if this is bigger you would see those two numbers four and two near this helium atom okay now i'm going to show you how to use those numbers to determine the protons neutrons and electrons so these two numbers one is called the atomic number and one is called the atomic mass we're going to start with the atomic number so given two numbers these are always going to have two numbers associated with each atom type or element type the smaller of the two numbers is always going to be the atomic number so with helium here the atomic number is two two is smaller than four so i know that's the atomic number down here with silver ag again you don't have to know that symbol but here are the two numbers and you can round 107 here up so 47 and 108 well 47 smaller this must be the atomic number so when this appears on a quiz or exam you're not going to have these labels here so it's important to know that the atomic number is the smaller of the two numbers provided to you along with a type of atom now this atomic number is going to tell us a couple of things as you can see here pointed out in this image the atomic number tells you the number of protons so that's how we know that helium has two protons down here silver the smaller of the two numbers is 47 that's the atomic number that tells us the number of protons silver has a silver atom has 47 protons okay and it actually tells us something else too the number of electrons but before we do that this is important here the atomic number is unique to each element okay so one element is not going to have or atom is not going to have the same atomic number as another element okay when you see a 47 atomic number that tells you that's silver this one two that's always helium etc with all the atoms or elements of different types now that atomic number also tells us the number of electrons okay and this is going to make more sense when we get into our next group of slides but we're going to deal with neutral atoms and that means the positives and the negatives the protons and electrons cancel each other out okay there's no overall charge because the number of protons equal the number of electrons so what that means this atomic number tells you another item it tells you the number of electrons in an atom the number of electrons is equal to the number of protons so this atomic number tells you the electrons so helium has two protons but also two electrons there's no charge positive or negative overall on this atom you don't see one right so the protons and electrons must be canceling each other out okay so that two that lower of the two numbers tells me that this has two protons and two electrons let's do silver this lower of the two numbers 47 that's the atomic number that tells you protons 47 protons but also the number of electrons 47. so those 47 positively charged protons cancel out the 47 negatively charged electrons that's why we don't have an overall positive or negative charge on silver okay and again that's going to make more sense when we go into our next unit too but for now that lower of the two numbers that atomic number tells you the number of protons and the number of electrons they're the same number if the number of protons and the electrons were not the same then there's an overall charge on an atom that atom is called an ion okay it would have for example a positive it would be like na plus that's sodium with a positive charge so that's an ion that's when the electrons and protons do not equal each other but for now we're going to deal with protons and electrons being the same electrons are important because they're the ones responsible for chemical reactions in other words the number of electrons in an atom is going to help you determine if that atom is going to interact or not and we're going to get some examples here coming up but let's do this other number the other number the higher of the two numbers associated with an atom is called the atomic mass or the atomic mass number so higher of the two so with helium imagine these labels were not there the higher of the two four is more than two right higher than two so that's the atomic mass of helium n a this happens to be sodium has these two numbers 23 and 11. imagine those labels are not there you go with the higher number that's the atomic mass or the atomic mass number the lower is the atomic number which we were just discussing down here this is chlorine cl the higher of the two numbers associated with it is 35 that means 35 is the atomic mass of chlorine whereas 17 is the atomic number sodium atomic number 11 lower of the two atomic mass 23 higher of the two now we're going to use this number to get our last particle so just do a quick review the atomic number tells us the number of protons and the number of electrons the lower of the two numbers associated with an atom but neutrons that's our third subatomic particle how do we determine the number of those well when you see this mass number again the higher of the two numbers that actually equals the number of protons and neutrons in an atom well remember the lower of the two equals the number of protons right so if you just subtract the two you're going to get this the number of neutrons so to get the number of neutrons all you have to do is subtract the lower of the two numbers from the higher of the two numbers or in other words the number of neutrons equals the atomic mass minus the atomic number okay so how many neutrons is in helium four minus two is two so helium actually has two protons two electrons because of the atomic number and also two neutrons so two two and two but all atoms are not like that so for example sodium sodium has 11 protons 11 electrons because of the atomic number how do we get the neutrons subtract 23 minus 11. so sodium has 12 neutrons chlorine has 17 protons and 17 electrons because that's what the atomic number tells you but subtract to get the number of neutrons 35 minus 17 is 18. so chlorine has 18 neutrons so just by looking at the two numbers associated with an atom and again you'd be you will be given a picture just like this you just have to know how to use those two numbers to get these three things the number of protons neutrons and electrons and we're going to use those three to draw some diagrams here coming up but before we do that let's go over this definition because it's relevant here isotopes what is an isotope well this prefix iso means the same so something's the same about isotopes isotopes refer to atoms and so right here in this image these are isotopes of carbon so what does that mean now if you look all of these have the same number of protons see here six protons six protons six protons the proton number that atomic number is unique okay that tells you you are dealing with a certain type of atom in this case all six protons that refers to carbon what is different well look at their number of neutrons that is different they're actually trying to show you a close-up of the nucleus where protons and neutrons are located this form of carbon has six neutrons this form of carbon has seven neutrons and this has eight neutrons well what's that going to mean well look at the other number this higher number 12 13 14. that's actually atomic mass see how it's increasing the more neutrons in an atom the more or higher i should say that mass is so an isotope we're talking about the same type of atom like carbon but different numbers of neutrons in other words the same type of atom like carbon but a different mass so this is still carbon but it's a form that has a lower mass compared to this form of carbon so they're all three of them are carbon because they have the same number of protons that's unique to an atom but they differ in the weight in other words they differ in the number of neutrons how did we get these neutrons subtract 6 the atomic number from the mass 12 minus 6 is 6. 13 minus 6 is 7 minus six is eight so they differ in their number of neutrons and therefore their weight okay and many elements or many atoms have isotopes the most common isotope of an atom that's the one that's usually included in the periodic table so if you look at carbon it's going to be this type in the periodic table it's going to be this carbon the one that has 12 and 6 associated with it because that's the most common type see here 98.9 of carbon atoms are this type okay so that's the one included in the periodic table these are less a lot less common compared to this one so these numbers are not included in the periodic table but it works the same way as far as figuring out the number of protons neutrons and electrons now some isotopes are radioactive so some forms of atoms are known as radioactive isotopes okay so they already have a different weight but they also spontaneously break down so for example this last form of carbon here carbon 14 goes by its weight name so carbon with an atomic mass of 14 the nucleus of this type of carbon is unstable it breaks off in a given certain given amount of time and forms other atoms okay other elements in other words so that's what this decay means the nucleus breaks apart suddenly okay and in some and i should sometimes it's sudden but certain radioactive isotopes take a long time to break down too so it depends but keep in mind that not all isotopes are radioactive only certain isotopes are but i want you to know the isotope definition and also know that there are radioactive isotopes now for example what are they used for okay some radioactive isotopes are used medically to trace something that's injected into an individual for example the pathway of blood through blood vessels within the heart or the brain there's this carbon isotope here this radioactive isotope carbon-14 is used to date fossils okay so in order other words to estimate how old a fossil is okay by looking at how many of this type of carbon has decayed spontaneously okay they can do that so definitely medical uses okay but also with uh fossil dating or rock formation dating in general now we're going to talk about electrons and electrons specifically are important because electrons determine whether an atom is going to participate in a chemical reaction so let's take a look at electrons there's a little bit of review electrons are found in the shells right the the energy clouds outside of the nucleus and often these are drawn in lines okay almost like a bullseye the nucleus is in the middle these images down here the nucleus is shown in gray okay the lines okay almost like little orbits those are the energy shells that's where electrons hang out so again important protons and neutrons in the center some of these diagrams even have the p and n right abbreviation protons and neutrons they're located in the nucleus and a given atom will have a certain number of them but electrons are shown in dots around these little orbits or energy shells and there's rules each shell holds a limited number of electrons and this is going to help you diagram these and figure out again this is where we're headed how do we determine if an atom is going to interact with other atoms and form a molecule in other words participate in a chemical reaction so we have to learn how to diagram these and i'm going to go over many examples on the last few slides too so take a look at this the first shell maxes out at two electrons and where is this show at well find the nucleus here's the nucleus center center this first line is the first shell okay the first little orbit not the outlining gray but this first orbit that's the first shell it holds a maximum of two electrons it doesn't mean there's two in there but it maxes out at two electrons the second one maxes out at eight electrons and that would be the second ring away from the center second ring second ring okay the third shell maxes out at 18 electrons again it doesn't mean that there's that many electrons in it but it holds a maximum of 18. and it keeps going but for the atoms that we're going to talk about that's important for biology we're going to focus on those these are this is all the father that we actually have to go and we're going to talk about this rule called the octet rule that doesn't apply to all atoms but it does apply to the biologically important atoms that's important to the human body okay so before we look at the octet rule i want to go through these pictures because this is what you're going to have to do examples of okay and we're going to go over some examples in the next group of slides so let's start with hydrogen here okay now hydrogen actually has the two numbers associated with hydrogen are one and one okay so hydrogen actually has one proton they're not putting one p in the center but it does have one proton and that means it has one electron see here this little blue dot see how that's in the first shell you fill up from the first shell and then go in the second and then the third if necessary so you fill out from the center out okay so hydrogen only has one electron so it's just the only electron in that first orbit let's look at this one magnesium happens to have 12 electrons and if you had the two numbers you could figure that out based on its atomic number it has 12 electrons what did we do first we fill the first shell it has two to fill that show so shell so it will then how many does the second shell hold eight do we have that yes we have 12 right total electrons so one two three four five six seven eight you do not have to put your electrons in pairs but it does make it easier i highly recommend doing that for counting purposes it helps keep you more organized so we can fill that second shell too because 2 in the first shell plus 8 is just 10 but i told you magnesium has 12 electrons so how many do we have left well 12 minus 10 is 2. that's why you see 12 or excuse me two electrons in the third shell notice it's not maximizing the third shell electrons it only has two so those two go in there so it has two in this third shell this outer shell by the way is called the valence shell the outermost shell in a hydrogen the outermost shell is only this first shell okay they're showing these empty shells here but we're talking about the outermost shell that actually has some amount of electrons in it that's the valence shell so here we go right here valence shell of magnesium has two argon here ar you can follow the the shells too okay argon actually has 18 electrons so you can see two in the first shell see this is an example of them not being paired and it kind of makes it harder to count so one two the second shell has eight and it fills it up right that's the maximum the second shell can hold how many do we have left we have two in the first shell eight in the second shell for argon that's 10. well 18 minus 10 is 8. we have 8 left over so it's not maximizing those 18 electrons that 18 electron max in the third shell but that's where we put the remaining electrons okay now why do we care well this outermost shell with electrons in it it's the third shell right for magnesium and argon but hydrogen is only the first shell that outermost or valence show is going to tell you whether that atom is stable and not going to react in other words it's happy not perform you know not participating in any chemical reactions or if it's unstable and therefore wants to react to get stable so let's look at this octet rule atoms interact to have eight electrons in their outermost shell now there are some exceptions to this okay we're again we're talking about what's relevant to biologically important molecules okay so atoms here's our rule if the outer shell called the valence shell and that's the shell that has electrons in it the outermost if it has eight it's stable and unreactive now there's only one in our example here that fits that the outermost shell with argon is this third shell and it has eight electrons that means that argon is happy it is stable with those eight electrons it's not going to interact with other atoms because it's already stable okay argon is actually in the very last column if you take back a look at the the periodic table see here ar this last column here these are actually called noble gases these are all stable they have eight electrons in their outermost shell they don't want to interact because they're already stable but that's not the case for most atoms take a look at magnesium the third shell is the outermost the valence shell it only has two that is not eight right octet octa means eight so what is magnesium going to do that means it's going to participate in chemical reactions it's going to be reactive there's different ways to say it it's going to be reactive it's going to interact with other atoms in order to get eight electrons in its outer shell so what's magnesium going to do it's going to either gain lose or share electrons to get eight electrons in its outer shell instead of this two okay because that's going to be the stable rule meeting this octet rule and there's different patterns and i'm going to go into those in the next set of slides when we get into chemical reactions how to tell if an atom will gain lose or share electrons to be stable we'll cover that next next set of slides for now i just want you to recognize this octet rule hydrogen is a little bit special it has just this first shell that's its valence shell and there can't be eight in that shell so hydrogen actually goes by a different rule since its first shell isn't full how what's the fullness fullness rule in the first shell would just be two right it is not full so hydrogen actually is unstable it's going to interact with other atoms in other words interact to get stable okay now we're going to do some more practice questions here we're going to put these rules and these diagrams and the octet rule all together to answer some questions and that's what's going to happen in these last few slides you won't have a copy of these but you can play back the video right and write these down in your notes follow along with me okay because this is going to give you practice on the study guide questions and help prepare you for the first quiz and this section of the exam in a few weeks so let's practice put all these pieces together to finish up here i'm going to give you three atoms so helium we've all seen these pictures before in the earlier set of these slides so helium sodium na and chlorine i showed you these images before to practice with the atomic number and atomic mass and how to figure out protons neutrons and electrons so i'll review that with you because that's the important first step then we'll look at the diagram and then this is the third question is that atom based on the diagram that you drew and the octet rule stable unreactive not participating right not interested in chemical reactions or will it perform chemical reactions to try to get stable so let's go back to helium h e helium is actually in this special category with with hydrogen because it's really small i'll show you in the diagram so let's practice helium has two numbers associated with it you would be given these numbers four and two the smaller of the two is the atomic number the bigger of the two the larger of the two is the atomic mass again you're not going to have these labels to help you out so you have to know higher number atomic mass lower number atomic number what do those two numbers tell you the lower of the two the atomic number tells you the number of protons and electrons so helium has two protons two electrons the mass if you subtract the lower number from the higher number the mass that'll give you the number of neutrons so helium has two neutrons four minus two so it's actually two two and two two protons two electrons two neutrons we're gonna use that information to do a diagram so take a look at this this would be your next step what are the two subatomic particles in the middle i have the center of the atom in gray here that's called the nucleus that's where the protons and the neutrons are and then you put the little numbers here how many protons did helium have well it goes by the atomic number two so p for protons two and so those two protons have a positive charge on them neutrons that's when you subtract four minus two two neutrons and they're together protons and neutrons in the nucleus okay and remember neutrons have no charge they are neutral where do the electrons go they go in the shells okay well how many electrons does helium have well we worked out before two what are the rules the first shell you fill up innermost shell right the first shell first that can hold two and helium has two total electrons so that's where you put the two so i in these blue dots that's my electrons i didn't put a minus but they do they are negatively charged okay the two negatively charged electrons cancel out with the two positively charged protons so overall this atom is is neutral no charge now let's answer this third question this is a special case again because we're only dealing with one shell we're not dealing with the higher shells that have a higher than a more of a max i should say um 8 or 18 depending on the shell so if you're dealing with hydrogen or helium then you got to go by the first shell rules helium has its first shell all filled up and that's its outermost shell well helium is stable that's actually why helium you may have noticed before is listed in this last column with the other noble gases it is stable but it doesn't have as many electrons it's small to be relevant for the octet rule but it's still stable most atoms are not going to be like helium and hydrogen you're going to be able to follow these general electron filling rules and the octet rule okay so helium is meeting that full first shell it doesn't have any more electrons but just filling up that first shell makes it stable so helium is stable and unreactive it is not going to participate in a chemical reaction let's look at another example sodium you've seen this image before again you're not going to have these helpful labels here so you have to know that the smaller of the two numbers associated with n a or sodium that's the atomic number and that gives you the protons and electrons so sodium has 11 protons 11 electrons the higher of the two numbers is the atomic mass how do we do the number of neutrons you subtract 11 from the 23. so sodium again has 12 neutrons 11 protons 11 electrons 12 neutrons that's step one then you do your drawing where do we put the protons and neutrons in the nucleus in the center protons 11 right you're going by the atomic number neutrons to get that you subtracted 23 minus 11. 12. so that's the nucleus of sodium electrons go in the little orbits or energy shells and they fill those up from innermost to outer most i did this one for you but let's take it step by step the first shell fills up with two and we have two we have 11 total electrons for sodium so you put two there the next shell maxes out at eight and we still have that many to give so one two three four five six seven eight eight in the second shell how many do we have left well two plus eight is ten and we have eleven total electrons so we have one left to put in that third shell this outer shell this third shell that contains electrons and it's the furthest out right so that's the valence shell of sodium so what's the octet rule you have to have eight electrons in that outermost shell for an atom to be stable so sodium does definitely does not meet the octet rule it is not stable okay it is going to be reactive it's going to adjust its electrons to try to get that eight in its outer shell and we're going to talk about how it does that when we talk about our next set of slides the chemical reaction section so one valence electron it does not meet the octet rule it is unstable going to participate in chemical reactions it will interact with other atoms to try to get stable last example chlorine we've looked at this before two numbers associated with it like always the lower of the two is the atomic number and that tells you both the number of protons and electrons so chlorine has 17 protons 17 electrons to get the neutrons you subtract the 17 from 35 so chlorine has 18 neutrons let's diagram fill up the first shell first with two well chlorine has 17 electrons so we certainly have two to put in the first shell second shell maxes out at eight again we have plenty of electrons for that so put eight in one two three four five six seven eight again that's where it's helpful to put the electrons in pairs it's easier to count and double check yourself so how many so far 2 8 that's 10 total and we have 17 so we put seven in that last show that third shell can it handle it yes because it can hold up to 18. okay so chlorine has one two three four five six seven electrons in its outer shell count your total to make sure you have the total electrons right 17 total so 7 in the outside 8 and 2 that total 17. is chlorine this final question fulfilling the octet rule no right it has 7 outer shell or valence shell electrons again we don't care about the inner most right only the outermost because these are going to interact potentially it has seven electrons in its outer shell not eight so chlorine is unstable it is going to be reactive it is going to interact with other atoms to try to get eight electrons in its outer shell to meet that octet rule so chlorine is definitely going to perform chemical reactions in other words form molecules so that's the first set of slides i'm going to talk more about when atoms interact so we know that when they are unstable they are going to perform chemical reactions we're going to talk about those interactions and how atoms what they do in other words to get that stable 8 valence shell number so we're going to talk about this in other words we're going to talk about how atoms can gain lose or share electrons to fulfill the octet rule and most atoms have to do that because most atoms do not meet that octet rule so this is going to set you up to understand the next group of slides the chemical reaction slides you can practice more of these types of diagrams in your sakheim book and it has answers already in there and there's also other practice questions posted as well that you can practice these diagrams make sure you take advantage of those you