this is the AP Chemistry Chrome study unit 2 molecular and ionic compounds and their properties in unit 1 we learned the atomic structure and its properties including periodic current now we know what an atom is now we're going to learn how to add on the interact with each other and form all different types of bonds so we're going to learn about ionic bonds covalent bond metallic bonds we're going to learn the structure of a molecule we're going to learn vasper Lewis Dot Diagram hybridization Etc let's get started so I always start from with the definition so what is a chemical bond so chemical bond is something that holds two atoms together chemical bonds hold atoms together and then to make sure that they behave as a unit so let's say for water which consists of two hydrogen atoms and one oxygen atom if you have just two separate hydrogen atoms and one oxygen atom in one single container then they do not have the property of the water when I say property of a water I mean it is the liquid at um room temperature it has a melting point of zero Celsius degree it is transparent it can dissolve salt and sugar all of these properties if you only have two hydrogen atoms and one oxygen atoms with no bonds in between them they do not behave out the water we don't call them water we just call them three separate atoms so we need to use chemical bonds to um to to connect these atoms together and then these three atoms they behave as one single unit called water okay um and chemical bonds especially important when it comes to I identified identify like the friend um different physical properties of a substance so let's say for graphite um and charcoal and Diamond all of these three consist of pure carbon so this is the picture of a diamond and a charcoal they have very different look um Diamond very expensive it's transparent it's shiny it's blingy um on the other hand charcoal it's fall it's black um it's dirty um so they have different physical forms or physical properties because of different bondings and different structures in between the carbon atoms this is why we learn chemical bonds and chemical bonds also play a very important role in determining the course of all the chemical reactions so chemical reaction is basically breaking up of old bonds information of new bonds so it's everything about the chemical bonds so let's say water goes from liquid phase to the solid phase it frees the serous also's degree then H2O in liquid converts into H2O in solid this does not chemical reaction because there is no breaking up of bonds or formation of the new bonds then so if I wanted to find something as a chemical reaction there must be something involved with the formation of new bonds or breaking up the old bonds so let's say when two hydrogen atoms um when the bond between the two hydrogen atoms break and then the bond between the oxygen atoms also break and the new bond between the hydrogen and oxygen forms um breaking breaking and then new bonds are formed then this is a type of chemical reaction okay so um let's go over all types of chemical bonds that we're going to learn in this unit we have ionic bonds and then we have covalent bonds and then we also have metallic bonds okay and for the covalent bond there are two types of covalent bond one is nonpolar covalent bonds the other one is polar covalent bonds we're going to dive deep into all of that in this unit so for ionic bonds usually it forms between a metal and non-metal and um for the covalent bond it usually forms between two non-metals murder metallic bonds of course it forms between the metallic cations so it's metal and Metal and this is the um this is the periodic trend of electronegativity that we went over in unit one and that we noted the trend of electronegativity is when you go from left to the right across the periodic trend electronegativity usually increases because the effective nuclear charge increased so the nucleus exert a greater attraction towards the shared electrons they drag the electrons like strongly when you go from top to the bottom usually electronegativity decreases because um the the energy level or the shell increases so the nucleus cannot apply that strong attraction toward the shared electrons okay um so for the ionic bonds usually um the electronegativity difference between two atoms are pretty big so let's say when you combine sodium in chlorine sodium has very little electronegativity of 0.9 and then chlorine has a pretty big electronegativity of this 3.0 the difference is 2.1 so um this is one of the factor that determines the ionic bond where the covalent bond it's usually two atoms with similar electronegativity or two atoms with electronegativity um would not so much difference um so let's say if nitrogen and oxygen forms a bond most likely it's going to be covalent bond because the difference in their electronegativity is only 0.5 but we're we're not going to go over on the actual number or actual value of the electronegativity difference in AP Chemistry you were not asked or required to memorize any of the electronegativity you only need to know those um periodic trend okay so types of chemical bonds um here is a example questions for AP style exam which of the following claims about a binary compound in which the bonding is ionic is most likely to be scientifically valid okay say ionic bond well what are some of the characteristic of ionic bond usually it forms between a metal and non-metal and then on the electronegativity difference is usually large um okay so out of a b c d a is not correct both elements are metals well no not both elements are metal that is metallic bonds B the atomic masses um are relatively small okay so atomic masses have nothing to do with the types of bonds um see there is equal sharing of electron between the atoms of the element in the compound okay so sharing of electron is about on the covalent bond we're going to learn about it later so it's not theater the electronegativity difference between the elements and the compound is in relatively large is a relatively large yes so D is the only answer and next um let's talk about um the ionic bond okay so ionic bonds form between two atoms when there is an electron transferred between two atoms so when electron transfer from one atom to another and here is a diagram that shows us the transfer of an electron so let's say elect atom a has one valence electron and atom B has seven valence electrons if there is an electron transfer from A to B then atom a becomes cation which is positively charged ion and atom B by receiving an electron it becomes an anion which is negatively charged ion okay and we know that light charges repel and unlike charges attract so cation and anion one carries positive charge the other one carries negative charge they're going to attract each other so they're um so a strong attractive force between two opposite charges form and these strong um attraction is what we call by ionic bonds so for example sodium chloride and sodium form is a sodium cation and then chlorine forms the chloride um anion so um cations and anions they attract each other or let's say magnesium oxide magnesium because magnesium cation and oxygen D comes oxide anion thank you there is a strong um attraction between two opposite charges which is ionic bond okay now let's talk about ionic compounds okay so these two are the common examples of ionic compounds the left one is table salt to sodium chloride on the right hand side that has calcium carbonate okay so both of the ionic compounds they are in the form of um they are in the form of a crystal and solid phase so ionic solids has Crystal letters structure Crystal lettuce is highly ordered structure of cations and anions here are couples of examples of the crystal crystal letter structure of different ionic compounds you guys are not required to memorize or differentiate any of these Crystal letter structure they are not going to be tested in a p chemistry exam but you just didn't know that um they um the ions are fixed in the position they are fixed um usually on each of the vertices of this Cube structure and cations and enter they're not free to move okay so the crystal letter structure um so this so this Crystal lettuce structure pretty much explains or contributes to the political property of ionic compounds such as the rigidity and then brittleness the rigid means that the structure um is hard it's not soft this is because of the strong ionic bonds now you can see that the ionic bonds there is ionic bond in between every single cation so this whole structure is very stable and it's not going to be easily compressed remember that you're going to apply imagine you are going to apply a force to compress it from top to the bottom then one two three four five six seven eight nine ten um 11 12 like 12 ionic bonds will support it so it's not going to be it's it's very difficult to change its shape um okay then what about brittle so brittle is a little bit different from brittle actually means it's easy to break when you apply other stress okay um so this is actually also because of the crystal letter structure so let's say you have this two-dimensional here is the two dimensional crystal lattice structure of some cation of some ionic compounds let's say you're going to apply a force on the right hand side on the right half of the sample then the right half of the sample will shift downward a little bit okay now um the cations and anions they're not right next to each other now the cations are right next to each other and anions are next to each other and light charges repel which means um the they will repel each other and eventually the ionic bonds are lost in between the left half and then the right half of this piece so it will actually break into two pieces also ionic compounds have high melting point and high boiling point so when a substance go from solid to liquid to gas it actually means that the bonds between the particles are weakened and eventually broken and ionic bonds are very strong which means it takes a lot of energy to break it this explains why High a lot of energy is required or high melting point high temperature is required to um to break the ionic bones um in um in the solid phase of ionic compounds and then convert them into liquid and ionic compounds are poor conductor of electricity and solid while they're good conductor of electricity in liquid and accuracy okay so um this might sound a little bit weird at the very beginning because um how come they have like these opposite properties okay all of these are due to the crystal letter structure so in the solid phase the cations and anions they are fixed in the position and they are not free to move which means there are no really moving ions there are no free ions to move um so a good conductor of electricity means there are free electrons or free ions and there are free to move around like within the substance then this substance is a good conductor of electricity in ionic compounds and ionic solids there are no freely moving um ions well if while ionic compounds are in the liquid or aqueous phase um the cations and anions are separate from each other they are still Loosely bonding to each other but they can glide around each other they are pretty much free to move so that's why they are good conductor in liquid and accurate state okay so molten or liquid sodium chloride is representing by the particulate diagram shown above which of the following indicates whether sodium chloride and liquid conduct electricity and best explains why or why not I literally just mentioned it it connects electricity because um the cations and anions there are free to move around so the answer will be B next the particular level diagram shown above best helps to explain which of the following properties of an ionic solid um okay so malleability and conductivity they are not the properties of ionic solids remember ionic compounds are good conductivity of electricity they're good conductor of electricity only when they're in the liquid phase or the active phase so not c not d and a density B brittleness okay so it should be brutalness because now on in the second diagram on the someone is applying a force on top left corner and then the right bottom corner so there is um there is a shift and now the light charges are next to each other and then there there is repulsive force in between them so they separate into two separate layers this is the brittleness easy to break when applying a force let's talk about coulomb fall which pretty much explains the strengths of ionic bonds according to Coulomb's law um the amount of the force in between like charges or unlike charges is determined by this Formula F is equal to K times q1 Q2 divided by r squared so no matter if it's positive charge or negative charge it carries a certain amount of charge and then we use Q to refer to the size of the charge or the amount of the charge so the greater the charges the greater the attractive force or the repulsive force and R refers to distance between the the center of the two charges so when two charges are far away from each other the force in between them either attractive or repulsive is small and when they get close to each other the force gets bigger um okay so we can apply this to the ionic solids so let's say for sodium chloride sodium is has carries positive one truth and chloride care is negative one charge so for them the q1 and Q2 is like positive one and negative one well of course we only dealt with the actual value so basically it will be one times one divided by the radius between them a radius squared and we're going to multiply by a constant K but K is um is a constant so it doesn't really matter when it comes to compare the ionic bonds of different ionic compounds um okay next let's say magnesium oxide so on the periodic table you can see the magnesium and sodium they are on um they're on the same energy level and magnesium has two um valence um and magnesium has one more effective nuclear charge which means magnesium cations mg2 plus will be slightly smaller than sodium cation on the other hand for the oxygen oxygen is on the second energy shell while chloride is in a energy shell so obviously oxygen will have a much smaller on atomic radius and ionic radius and then chlorine or chloride okay so this will be a diagram of sodium chloride and magnesium oxide so um the radius or the distance between sodium and chloride ions will be this much while the distance between the magnesium and oxygen will be this much which is much smaller okay so I'm going to use capital letter R to represent the distance between the nuclei of sodium and chloride I'm going to use a small letter R to represent the distance between a nuclei of magnesium and oxygen then for the magnesium oxide the charge will be 2 times 2. okay the charge is greater and then the distance is smaller so which means this whole ratio will be much greater for magnesium this is large and this is small so so magnesium oxygen ionic bonds will be much stronger than the sodium chloride ionic bond which means magnesium oxide will have a higher melting point and it is a better conductivity conductor of electricity and it's more brittle and it is more rigid next is the covalent bond the covalent bonds form when two atoms share electron rather than when there is a transfer of the electron um and as I stated before there are two types of covalent bonds one is polar the other one is nonpolar so non-polar covalent bond forms when the electrons are shared equally between two atoms and polar covalent bond forms when electrons are shared unequally between two atoms okay then how do I know which one and which molecule electron and which bonds like electrons are shared equally and in which month electrons are shared on equally so we're going to take a look at the identity of the two atoms so if it's identical atoms like um chloride chloride covalent bond then of course this will be non-covalent Bond because they're they're twins they're exactly the same so they pull they pull the electrons with exactly the same amount of force um then what about water molecule H2O so hydrogen and oxygen oxygen has a way way way bigger electronegativity on based on the periodic trend that we learned in unit one which means oxygen is very very strong when it comes to pulling the electrons toward itself okay so even though hydrogen and oxygen are sharing two electrons but oxygen is occupying these two electrons most of the times so hydrogen barely gets to share the electrons and oxygen gets to share the electric difference most of the times um so in this case hydrogen oxygen bond is a polar covalent bond okay and within the molecule due to the polar covalent bond we will have um the partial negative charge and partial positive charge separated in in a molecule that a more electronegative atom will carry partial negative charge which is represented with Greek letter Sigma so Sigma minus means partial negative charge and two hydrogens will carry partial positive charge um Sigma positive so here is a comparison between ionic bond and then two covalent bonds in ionic bonds there is a transfer of whole number of electrons so no sharing of electrons between two atoms or two ions so that's why you don't see any of the sharing or any of the bond between or any of the connection between um two sides of the cations and anions on the other hand vertical covalent bonds they Shear electron so electrons move back and forth between two atoms electrons move back and forth so that's why use as you see that it's a whole one one single electron cloud between two atoms and for the non-polar covalent bonds electrons are shared equally so it looks symmetric the electron cloud low symmetric vertical and covalent bond the electron cloud looks much bigger on the more electronegative side of uh of of the molecule um which of the following claims about a binary compound composed of elements with the same electronegativity is most likely to be true same electronegativity means two atoms pull or attracts the electrons with the same Force um so they're going to share electrons equally so it is most likely non-prolar covalent bonds um so the answer was B next how do we determine covalent bond length um okay so covalent bond links is determined by this potential energy versus internuclear distance diagram um so here is an example of hydrogen gas H2 so two hydrogen atoms um they have to be close to each other to start forming some kind of Attraction when two hydrogen atoms are like far away like far far away from each other they don't repel they don't have repulsive force or attractive force in between them they just have no interaction at all they are just two separate atoms in this case because there is no interaction at all the potential energy will be equal to zero okay what if two hydrogen atoms are very very close to each other so their nuclei are almost um in the same spot okay so nucleus carries a positive charge so when two nucleus the two nuclei are too close to each other there will be strong repulsive force in between them okay so strong repulsive Force means it's a very unstable State um so unstable means high potential energy so when two hydrogen atoms gets closer to each other then the um then the potential energy increased abruptly okay uh whatever there are kind of um separate from each other and then there is like slight overlap of the electron cloud okay then in this scenario there will be some kind of attraction there will there will be some attraction between the nucleus of let's say atom1 and then the electrons of the hydrogen atom two and vice versa so because there is still some attraction going on so they're gonna they're gonna pull each other closer um okay so at a certain point the nuclei are close to each other um and then the attraction between the nucleus and electrons and the repulsive force between two nuclei kind of balance out so this is the perfect point of balance um and each of the molecules have different balance point um so when the 74 um picometer is the balance point for the hydrogen hydrogen bond okay so at this balance point it is considered the most stable um it's the most stable State um and that's why the potential energy is the lowest so low potential energy means it's very stable okay so according to this curve I can easily figure out the the covalent bond length of hydrogen gas because there's a minimum point in this pink represents the covalent bond length of hydrogen hydrogen hydrogen hydrogen bond and let's try to compare different types of the covalent bond single double triple so depending on the number of the electrons shared by two atoms we classify them into a single double and triple when two atoms share two electrons then this is a single Bond when they share four electrons this is a double bond and when they assure six electrons this is a triple bond and um for for um and the more more electrons a two atoms share um and it means that there are more overlap of the electron cloud and then the stronger Bond length and the shorter the button length so from single to double to Triple the bond length actually decreases so the single the carbon carbon single bond is the longest and then the carbon carbon triple bond is the shortest while the triple button is the strongest and a single bond is the weakest okay which of the following correctly compares the strength of two carbon carbon um Bonds in the molecule represented in the Lewis diagram shown above so two carbon two carbon bonds okay so on the left side there is a carbon carbon um double bond on the right side there is a carbon carbon single Bond and we're comparing these two bonds um of course double bond is stronger and shorter than the single Bond so the right answer will be um a the carbon to carbon Bond on the left is stronger because it is a double bond and the next electron cloud so on the left this is the Bohr model that we learned in unit one on the right side this is the electron cloud model the electron cloud model is a more advanced or more modern um atomic structure that we that we study or that we believe to be true in a modern chemistry so even though Board model is partially true it is true that electrons reside on certain a specific energy levels um but they don't really follow this orbital the circular orbital strictly so rather they are actually very random they are they move very randomly and then they move on in a very randomic path okay so um these dots represents the possibility of electrons to be found around the nucleus so um more color around a nucleus means it's more likely for electrons to be found within this region and then this region and then out of this it's not not very likely to bound electrons um so when we refer to shearing of the electrons we're actually referring to overlap of the electron cloud okay and depending on the type of the sharing we can classify on the the covalent bond into Pi Bond and sigma bonds a covalent bond is sharing of electrons which is basically overlap of electron clouds and as I said a sigma Bond and Pi Bond okay so Sigma Bond so Sigma Bond occurs when orbitals um overlab had to head so it can be between two s orbitals okay so this is two two of the S orbital s orbital and S orbital and um this will be right in the thinner this is the overlapping part okay overlap of the electron cloud and it can be overlap of the two P orbitals again this is the overlapping part and it can occur between s orbital and p orbital okay and then we call this hat to hat overlap and then remember the overlapping part it's always on this inter nuclear axis so internuclear axis is a line or is an axis that um that passes through the nuclei of the two atoms okay and then the overlapping part the overlap of the electron cloud is always on this internuclear axis that's the features of a sigma Bond on the other hand for the pi Bond occurs only when two P orbitals overlap and then while they are parallel to each other so rather than half to head it's going to be two parallel P orbitals and this is the overlapping part and this is the internuclear axis so for the pi bonds the overlap of the electron cloud is above and below the internuclear axis it's not on the internuclear axis so that's the difference between pi Bond and sigma Bond and then Pi Bond and sigma Bond they combine to form single Bond and double bond so for the single Bond it's always the sigma Bond it's always one Sigma Bond where the double bond it's always one Sigma Bond and one Pi Bond for the triple bond it's always one Sigma Bond and then two Pi bonds next is the metals so these are um some of the metals including gold silver copper zinc um Etc so metals usually um they are solid and then they are hard and then they are they're also shiny so we can use the structures of metals to explain on its physical properties so this is the structure of metals in three dimension and this is what you usually see in your textbook on or on your test so Metals um and and metals consist of the metallic cations and then the localized electrons when I say delocalized electrons I mean electrons are free to move electrons are not bound to each of the um the metallications on the other hand um the metallic cations they are highly organized just like the cations and anions in crystal lattice structure of ionic compounds so it forms lettuce of metallic cations and then it is surrounded by delocalized or free electrons and then sometimes we call this electron C model because it is like metallication submerged in water of the Sea of the electrons and the electrons just like water they're free to move between all the cations so again electrons are delocalized or they're free to move okay so then it's very obvious that due to the property of the the localized electrons um the metals are good conductor of electricity no matter um no matter they are in liquid or gas or solid phase and metallic bonds when we refer to metallic bonds it's actually the attraction between um the metallic cations and the Lee localized electrons okay so I would explain why it's a good conductor of electricity because of the really moving the electrons and um Metals okay metals are malleable and ductile so malleable means you can actually stretch the metals um to make them a very thin sheet ductile means you can stretch it to form a very thin wire so basically it means metals or stretchy to some extent um and then this is also due to the electron C model or the structure of the metal okay so this is the metallic cations they form a lettuce um they're highly organized and then in between them we have this uh freely moving electrons these electrons are free to move and then the obstruction between the metallications and electrons are considered metallic bonds um so um okay now let's see so let's say now I am gonna um compress it um I want to compress it to a very thin layer okay then these cation the metallic cations will Glide around another metallic cations okay and these electrons because it's free to move so it will move together so now it's going to fill in the space in between these two metallic cations okay then what about this part okay now let's say I'm going to compress it I'm going to apply a force and then um press it to very thin sheets one more time okay so these metallic cations it's going to fill in the the the space between these two metallications and again because electrons are free to move so they are just going to fill in the space between these um metallic cations and anions and that's the same for this part So eventually because of this a free freely moving electrons um so metals can be stretched into a thin sheet or very thin very thin wire without breaking okay the diagram above best illustrates which of the following phenomena associated with the solids that have metallic bonding um obviously um it's applying the force on both sides so um you they it's trying it's also someone is trying to um someone is trying to um like stretch it okay um and this is either malleable or ductile so it's going to be B and now let's see if the reasoning is correct because it shows how adjacent layers of positive ions can move relative to one another while remaining in full contact with an electron C okay so again this is considered on all of the space between the calories this is considered electron C so even though the cations are right next to each other because the the space in between them are filled with electrons so they do not repel each other so it's going to be B the malleability next which of the following indicates whether the solid substance represented by the particular diagram shown above conducts electricity and explains why or why not so positive ions they're in this highly ordered the letter structure where electrons are just freely dispersed in between them um so which means positive ions are fixed they're fixed in a position they're not free to move but the electrons are free to move so um a it conduct electricity because it is made of positive and negative particles of course it's not such as cations and anions and anions and ionic solids um they are not free to move so it doesn't connect electricity B it conducts electricity because electrons are free to move through the structure yes B is the right answer see it doesn't conduct electricity because the electrons are strongly attracted to the specific positive particles so this is not true at all so electrons are delocalized in metals D it does not conduct electricity because the positive particles are not free to move yeah this is true but it doesn't mean that electrons are not free to move either so D is not right next alloy so aloe is the mixture of different um Metals so let's say for example when you mix on Silver and copper um so in most of the jewelries um it's not pure silver it has some of the a certain percent of the um the copper mixed in it to make sure that um it's um it's durable so some advantage of aloe is it's harder and stronger less malleable and less ductile than pure Metals um so they can be used and used for let's say cooking for construction as a jewelry so they're more durable okay um so even though usually alloy is a mixture of different Metals sometimes it can be the mixture of metals and nonmetals such as still so still is the mixture of iron um Fe and carbon which is a non-metal but um 96 to 98 of still is iron the primary component of still is still the primer the primary component of aloe is still um still metal so um it is still considered a mixture of the metals and for still when you add carbon in it it actually increased the um the strength by a lot so still is used in construction site a lot of times and there are two types of alloy depending on the size of the the substance in the mixture one is interstitial alloy the other one is substitutional alloy I'm going to talk about substitutionality first so uh breasts um or or bronze um they are usually on the substitutional alloy so zinc and copper they have about the same size um so when you um when you mix a little bit of zinc in Copper the zinc will just replace um the the copper the copper cations because of the similar size so it just replace the copper it just takes the place of the copper so it's substitutional Alloy on the other hand let's say in in still on the carbon is like so much more so much smaller compared to Iron so when um in in the lettuce structure of the of the iron cations um there is Tiny space in between the ions because um they're not Square they are not Cube um they're like round they're spherical and carbon just fills in this space in between them because of the small size um and this actually blocks the metallic bonds or it actually blocks the um Iron it actually blocks the Iron Man cations from moving around each other um submerged in this electrency which increased the rigidity which of the following particular particular level diagrams best represent an interstitial alloy interstitial means one of the one substance of the mixture it has large Stars large size the other one has a small side so the smaller one just fits in the empty space in between the big um the the big cations so this is going to be a next is the Louis dot diagram so we are going to learn a Louisa diagram and Vascular all together to determine the structure or three-dimensional shape of a molecule so this is especially important in unit um in in unit 2 and unit 3 we're going to utilize what we learn in unit 2 um to go further on intermolecular force so you need to have a very good understanding on this topic so um what I mean by the Louis dot diagram is it is a diagram that shows how atoms are bonded to each other within a molecule instead of single bonds is it a double bond let's say for carbon dioxide CO2 what is the order is it carbon oxygen oxygen or oxygen carbon oxygen okay so we deal with all of this in Louisa diagram it shows the atomic Arrangement it shows the arrangement of the atoms within a molecule and to draw a appropriate Louis dot diagram we have to follow couples of rules so let's take a look at the first two one is the number of the valence electrons so let's say in oxygen gas O2 so each of the oxygen has only six valence electrons which means two of the oxygen has two times six which is 12 valence electrons in total so when you draw the Louisa diagram of oxygen you cannot have more than 12 valence electrons this is the most important thing this is the rule of thumb the second is each of the ad on redundant molecule have to achieve the full OCTA state so full autistic means eight valence electrons or two valence electrons per hydrogen and helium because OCTA state is the considered on the noble gas State or the most preferred State um okay so how I do it is actually very simple so for oxygen too I know that its chemical formula is O2 okay um and um for to make sure that each of the oxygen achieve the full artist State then each of the oxygen should be able to have 2 times 8 16 valence electrons in total but actually I am given only 12 valence electrons which means now this oxygen gas structure is four electrons short this actually means they are sharing four electrons um in this oxygen molecule so it will be oxygen oxygen atom and sharing one two three four four electrons okay then what about the lone pair electrons of the oxygen well each of the oxygen has six valence electrons so six minus the number of electrons shared which is four that will be two for each of the oxygen to achieve um a full OCTA State um they have to carry they have to eventually um get to have eight valence electrons so eight minus the number of the um bonding pair electron four which is equal to four this means the oxygen has four lone pair electrons and this is a symmetric structure so the oxygen on the left side also carries four lone pair electrons okay now let's check if this is the correct Louis dot diagram so one two three four five six seven eight nine ten eleven twelve so 12 valence electrons in total okay correct and then next um octet rule okay so for the oxygen on the right it has one two three four five six seven eight eight valence electrons for the oxygen on the left it has the one two three four five six seven eight eight valence electrons it's cleared so this is the most appropriate Louis dot diagram for oxygen gas O2 um for four electron is shared I can use um I I can use double plus to represent it so oxygen oxygen double bond and then each oxygen carries four lone pair electrons okay um so next we can try to draw the Lewis dot diagram of nitrogen using exactly the same method so let's say nitrogen N2 okay so each of the nitrogen carries five valence electrons which means two nitrogen carries um 5 times 2 10 valence electrons and for to make sure that all the nitrogens achieve the full octave State then it's 2 times 8 which is equal to 16. okay so we want to have 16 electrons in total but we have only 10 which means um I am gonna share six electrons so two nitrogen atoms share six electrons so nitrogen nitrogen one two three four five six okay then how many lone pair electrons does each of the nitrogen have well eight minus six is equal to two which means each of the nitrogen has two lone pair electrons and now let's double check one two three four five six seven eight nine ten okay ten valence electrons then each of the nitrogen carries one two three four five six seven eight eight valence electrons so it fulfills the octane rule okay so that's it so this is the nitrogen nitrogen triple bond and the nitrogen gas will be start diagram okay um and next is Boomer charge so most of the times we are able to draw the appropriate release that diagram based on the first two rules but sometimes we are able to draw multiple possible Louis dot diagrams and then we will have to take a look at the formal charge um okay so for more charge how we calculate it is um it is the number of the valence electrons minus on the number of the lone pair electron minus the number of the bonding pair electron divided by two okay um and um here's an example of um here's an example of phosphates po43 minus okay so there are two possible Louis dot diagram one is phosphorus in the center and then it's Bonnie 2 for oxygen by four of the single bonds so it's for phosphorus oxygen single Bond h of the oxygen carries six valence electrons um six are lone pair electrons and then the second will be both first in the center and then it's Bonnie to one Oxygen by uh double bond and then it's bonding to three other Oxygen by single bonds okay now let's try to see um okay and then both of the Louisa diagram fulfill the first two first two um first two rules okay and now let's try to calculate the formal charge for each of the atoms okay so for this Louis dot diagram the phosphorus has number of the valence electrons is five okay minus number of the lone pair electron is zero number of the bonding pair electron is one two three four five six seven eight so eight divided by two that is equal to five minus four which is five minus four which is equal to one so the first first care is positive one charge what about the oxygen around it these four oxygen they have exactly the same structure they're all symmetrics so I just need to do math one time so the number of the valence electrons is six six minus number of the lone pair electron is six and then the number of the bonding pair electron is two so 6 minus 6 minus 1 that is negative 1. so negative one negative one negative one negative one so in total when you add them up um you will get the charge of this polyatomic ion which is negative three okay what about this uh Louis dot diagram so again I'm going to start from phosphorus both first has five minus lone pair electron zero minus um the bonding uh pair electron one two three four five six seven eight nine ten so ten over two which is zero okay and the oxygen these three oxygen have symmetric um structure so um six minus six minus two over two that is negative one so negative one and then this oxygen would double bonds um has former charge of six minus four minus four over two which is equal to zero okay so now let's try to compare these to Louis start diagram okay so one two three these three oxygens um surrounding phosphorus they carry exactly the same form of charge so we don't even have to consider them we only need to take a look at the first the central atom and then the oxygen on top of it okay so on the left Louis start diagram both first carries positive one charge and oxygen cares negative one charge on the right both carrots charge up zero so for formal charge um when this number is equal to zero this is the best this is the most appropriate one so compared to one or negative one or even two or negative two zero are considered the best the most stable so um the lowest darker on the right this is the most appropriate of structure Lewis dot diagram of the phosphate okay so this is one case of the form of charge um in which um we're in charge of zero is always preferred okay so there is the second scenario in which you will not you don't have uh from a charge of zero on on the other hand you have a formal charge of um one and negative one so thio cyanide s c n minus there are two possible um bully stat diagram as well so one is sulfur um carbon single Bond and then the carbon nitrogen triple bond um in one two three four five six um and one two the other one is sulfur on carbon triple a double bond and then the carbon nitrogen double bond one two three four one two three four again let's try to calculate the formal charge of each of the atom in each of the Louisa diagram I'm going to start from the left one so the sulfur has the former charge of six minus the valence electron um six minus number of the lone pair electrons six minus the number of the bonding pair electrons divided by two two over two so six minus six minus one that is negative one and a carbon that is number of the valence electron four minus number of the lone pair electron zero number of the bonding pair electron over two so it is equal to zero so nitrogen has the valence electron of five lone pair electron up two bonding pair electron is six over two so that is equal to zero so it's negative 1 0 0 for this one and for this one again I'm going to start from sulfur sulfur carries a 6 minus number of the lone pair of electrons four minus number of the bonding pair electrons four over two which is zero the carbon has four minus zero minus eight over two which is zero the nitrogen has um number of the valence electron 5 minus the number of the lone pair electrons four minus number of the bond being pair electron divided by two so five minus four minus two which is negative one okay so when we compare these two electrons these these two Lewis Dot Diagram um both of them carries um two zero former charge and one negative one form are charge the only difference is in the left one the sulfur carries the negative one from a charge on the right one the nitrogen carries negative one form of charge okay so we cannot minimize the formal charge anymore then we need to pay attention into these two atoms which carries a non-zero from a charge or negative one form of charge okay so sulfur and nitrogen which one is more likely to carry a form of charge of negative one so a more electronegative atom tends to carry a more negative form of charge and on the periodic table when we compare the sulfur and nitrogen so nitrogen is actually the third most electronegative element in the whole periodic table so nitrogen is more electronegative than sulfur which means nitrogen is more likely to carry that extra negative charge than sulfur so um nitrogen carrying negative one and sulfur carrying zero is more appropriate than nitrogen carrying zero and sulfur carry negative one so the Louis dot diagram on the right side is a more appropriate Louis dot diagram okay which of those diagrams above best represents the H2O molecule and Y diagram 1 and diagram two okay so it's very obvious then diagram one is not an appropriate one appropriate one because the central atom carbon it has only one two three four five six um six um a sixth bonding pair electrons so it does not even fulfill the full oxide so if we ever calculate the former charge of these two um the diagram one will have non-term from a charge on on carbon the formal charge of the carbon will be equal to um four minus zero minus six over two which is equal to one so um the diagram two will be more appropriate and this is because all the atoms have a formal charge of zero next on carbon dioxide CO2 which of the Lewis diagrams shown above is the more likely structure of carbon dioxide and why okay um so um for the diagram one the carbon in the Saturn carries the former charge of 4 minus zero minus eight over four which is equal to zero and the oxygen on both sides carries former charge of six minus four minus four over two which is equal to zero so all of the three atoms in diagram one carries form a charge of zero what about diagram two the um the central atom carbon carries four minus zero minus eight over two which is zero from a charge of zero the oxygen on the right side carries six minus two minus six over two which is one okay so positive one the oxygen on the left carries um six minus six minus two over two which is negative one so obviously diagram one is a preferred or it's a more appropriate Louis start diagram because it has smaller form of charge all of them are zero so um um diagram one either A or B and because all the atoms have a former charge of zero so a is the right answer based on the former charges which of the following is the best um Lewis electron dot diagram of h3no based on the former charges which of the following is the best Lewis electron dot diagram of h3no um okay so H3 and O again we will have to calculate the formal charge um so I am a little bit lazy so I'm gonna pay attention to nitrogen and oxygen specifically so for nitrogen and oxygen um if I ever calculate the formal charge then in a the former charge of nitrogen will be 5 minus number of the valence electron lone pair electron 2 minus the bonding pair electron 6 over 2 which is zero and the oxygen is 6 minus one two three four six minus 4 minus uh 4 over 2 which is zero so obviously a is the most appropriate one because both nitrogen and oxygen have former charge of zero I don't even have to calculate the form of charge of the other three next is the resonance structure okay so in some of the cases we will observe that um when for my charger exactly the same there are still um a variety of the possible Louisa diagrams uh for one single molecule or for an ion so let's say for ozone um O3 um okay so I'm going to start from the Lewis Dot Diagram by using the by applying the first two rules um so first off three oxygen means it's three times six eighteen valence electrons are available to achieve the full autistic it is 3 times 8 24 electrons and 24 minus 18 is 6 it means six electrons are shared between three of the oxygen atoms and it is impossible to share three electrons and three electrons so it has to it's because the number of the electrons shared in a covalent bond has to be multiple of two like two or four or six so two of the oxygen atoms share two electrons while the other two oxygen atoms share four electrons okay and okay so for this oxygen to achieve the full octane State um eight minus 4 is equal to four which means it has four lone pair electrons one two three four and for this oxygen eight minus two is equal to six so it has a sixth lone pair electrons one two three four five six for the central oxygen it will be eight minus um two minus four which is equal to two so two lone pair electrons so um oxygen I'm sorry ozone ozone basically have oxygen oxygen single Bond oxygen oxygen double bond okay but is it possible that the oxygen two oxygens on on the left side carries the double bond and then the oxygen on the right side carry the single Bond yeah absolutely possible so oxygen oxygen double bond and oxygen oxygen single bond this is also a possible structure of Illusion and these two have exactly the same formal charge so it doesn't really matter um which one has a lower form of charge or not um okay so for these type of um um for these type of um Louis start diagrams we call them resonance so there are two resonance structures for the ozone molecules okay and eventually uh when you actually observe an ozone molecule in in nature you will actually see that two um two oxygen oxygen um covalent bonds are actually of the same length which means in the nature They Don't Really differentiate between a single Bond and a double bond in nature they take this resonance hybrid structure which is an average of these two resonance so retina's hybrid so they're going to mix one single Bond and one double bond together and take an average which is one and a half bonds so um three of the oxygen they're going to have exactly the same bond in between two it is like one and a half months okay and here is another another example of resonance structure um carbonate co32 minus the carbon is the central atom um and then there is a carbon oxygen double bond and then two of the carbon oxygen single Bond and again um the carbon oxygen double bond can be between this oxygen and carbon where it can be on this side or it can be on the this side So eventually I will be able to draw three the retinal structures of carbonate and when you do the resonance structure you use the double-sided Arrow to collect them which means that they can switch between each other and again um in nature when you have a carbonate um carbonate ion you are actually going to observe resonance hybrid structure so each of the carbon oxygen Bond will be equal to the other two okay so there are sharing two single bonds and one double bond so each of the carbon oxygen bonding will be four over three four thirds Bond so it is represented as a solid line and a dashed line and carbonate as a whole it carries a charge of negative two and then the charge of the negative two um is also shared in between three of the oxygen atoms So eventually each of the oxygen atoms carry negative two-thirds charge next is overfilled versus Under filled so these are actually the exception to the full octet okay so remember that the full octet so eight valence electrons except for two valence electrons per hydrogen and helium these These are considered the most stable or the most preferred state for all the elements in the periodic table the thing is sometimes for some of the molecules it's just impossible to arrange electrons in a way that they achieve the full author State there are just way too many electrons or way to fuel electrons it's just impossible to have that then for these these elements or or for these molecules we're going to allow for overfilled octet or under filled octet which means even though the number of the valence electrons is not eight we still consider it to be as stable as octastate so under field usually occur when the central atom is um the group two or groups three elements and um the the halogens are bonding to the central atoms so let's say for um beryllium dihydrite um the beryllium is group two and it has two valence electrons so it can form only a maximum of two single bonds so beryllium dihydrate beryllium um having four valence electrons only this is an example of underfilled octet beryllium it has only four valence electrons but still it's considered the octet State like the very stable the most preferred State and another example will be Boron trichloride so Boron which is a group three element it has three valence electrons only so when it forms a single bond with chlorine it can form three bonds only so this is the best that it can do so even though the boron has only six valence electrons it is still considered to be as stable as a full octet okay then what about overfilled the overfilled octet usually occurs when the central atom is on the element in group five six seven or eight so let's say it's done so that one is a noble gas and usually you know noble gas does not really form a bond with another element but there are some exceptions and then on is one of them so let's say Denon um um hexafluoride um xcf6 then the xanon is in the center it has one two three four five six okay and since the dunno has eight valence electrons then it will so overfilled over filled octave usually occurs when the central atom is the group five six seven or eight on um atoms so let's say Noble get that on usually noble gas does not form any of the bond with um other elements but there are some exceptions so let's say Xenon tetrafluoride on the Denon forms four single bonds with the halogen fluorine okay and since the dunno has eight valence electrons so uh now it has four four electrons left so these four electrons will be the lone pair electrons of the Denon so in total Denon has one two three four five six seven eight nine ten eleven twelve so xano will have um 12 valence electrons so even though this is way more than eight this is still considered the octet state or very stable state so another example will be something like pcl5 of those first pentachloride um and then Etc and finally Vesper of Bayless show electron pair repulsion okay so Vesper is extremely important in determining um the three-dimensional shape of a molecule um and how it does it is by minimizing the electric electron repulsion okay so valence show electron which means um it only occurs um in between the valence electrons and then the pair means that they the electrons always have to be impaired either the lone pair or the bonding pair and the repulsion okay of course um it refers to the repulsion between the lumpier electrons and the repulsion between the bonding pair electrons the repulsion between bonding pair and lone pair electrons okay so what's really important here is you will have to know the Lewis Dot Diagram first and then based on the Lewis Dot Diagram you can try to figure out the three-dimensional structure according to Vesper so um the lowest diagram is the first step and then the next step will be Vesper okay um the thing is a lot of people think or they believe that Lewis Dot Diagram is the thing is a lot of people believe that Louis start diagram is already the molecular geometry of a molecule which is completely wrong so let's say for sf6 um sulfur hexafluoride if you draw a Lewis diagram then it looks like this so this looks like a two-dimensional structure um as sulfur as the central atom and then fluorine is surrounding it just like um like the slices of the pizza and it's two-dimensional this is not true at all so if you try to um to to model it in 3D then it shows this um this three-dimensional three-dimensional okay hero shape and then each of the fluorine sulfur fluorine bond is 90 degree rather than 60 degree um so Louis does not tell us anything about the three-dimensional shape so we always use Vesper to determine the three-dimensional shape when we refer to molecular geometry it is exactly what we mean by the three-dimensional shape again Lewis diagram only tells us about the arrangement of atoms okay so um there we are going to take a look at on five different categories um and we're going to start from the electron pair number of two so usually we write them as MX2 which means on the central um the central atom m is surrounded or bonded by two electron Pairs and one is the electron pair it refers to both lone pair and the bonding pair electrons okay so for example um the most typical example example of MX2 will be carbon dioxide CO2 okay so I will start from the Louis structure of carbon dioxide it's carbon oxygen double bond carbon oxygen double bond and therefore um lumpier electrons on each of the oxygen okay so around this Central atom of carbon I have only two electron pair well there is no lone pair and then um the bonding pair is two only so a single Bond double bond triple bond all of these are considered one bonding pair okay so um these two long electron pair electron because electron and they repel each other because the light charges repel so they are trying to be far away from each other as much as possible um so they will be on the opposite side there will be exactly 180 degree away from each other so this contributes to the linear molecular geometry or linear shape okay and then when we call this electron domain geometry when we consider both lone pair and bonding pair and then when we consider the bonding pair only we call it molecular geometry later you will know what that exactly means okay and next MX3 this is when Dustin her atom has three electron pair around it okay um so let's say bcl3 Boron trichloride again I'm going to start from the Lewis Dot Diagram so Boron chlorine is single Bond okay okay again um the it has only three electron pair one two three with no lone pair electron and then if you want these three electrons here to be further furthest away from each other as much as possible then the most then the structure they form will be this trichonal planar shape so on this plane they are like 120 120 120 away from each other this minimize the electron pair repulsion between the electron pair okay now it comes from it comes something tricky what if one of this bonding pair is the lone pair instead so let's say for ozone so um oxygen oxygen single Bond oxygen oxygen double bond and then the center for oxygen also has a long pair of electrons okay so um the central oxygen has one two three three lone pair of three electron pair okay so to minimize the electron electron repulsion they are one 20 degree away from each other okay so it has the trigonal planar as the electron domain geometry for electron domain geometry again we are taking accounts the lumpier electron as well okay but when we actually name the structure of the ocean we call it bent rather than the trigonal planar because when we consider the structure or or in the molecular geometry we don't account we don't count the lone pair electron we only cause the bonding pair or we only count the the atoms so for the molecular geometry we only consider these parts so that's why we call it bent next it will be mx4 okay so ms4 is actually one of the most common molecular geometry that we see in AP Chemistry test and one of the most common example the most known example will be CH4 the methane so carbon in the center and then with four carbon hydrogen single bonds okay so this is the Louis start diagram of methane um and obviously the carbon the central atom um has one two three four four um um for for electron pair okay so um when when four electron pairs um our furthest away from each other in three dimensional structure they actually form this weird like tripod kind of shape so it's just like the tripod and then this is a tripod and then you have another stick that's pointing upward let's say to put a camera on so this is the exactly the same shape as the tetrahedral structure so um each of the bonds are the 109.5 degree from each other and they're perfectly symmetric what I mean by that is when you rotate it when you rotate it by 109.5 degree so this part is pointing upward then it looks exactly the same as this structure next is when one of the uh when when one of the when when one the next it is the next when uh one of the four Bond pair next when one of the four bonding pair electrons is replaced by the lone pair electron then it's going to form this trichonal pyramidal shape okay because you have only the tripod legs and then not the not the supporting stick anymore so one two three and it is like a a pyramid but the bottom will be the base will be a triangle so that's why we call it trigonal pyramidal and the most common example will be NH3 ammonia so nitrogen hydrogen hydrogen there are three nitrogen hydrogen and single bonds and then the nitrogen also has the lone pair electrons um so um it has one two three four four electron pair including the lone pair so it has the tetrahedral electron domain geometry again but when we name it when we need the structure of the ammonia we don't really take accounts the lumpier electron we only consider the tripod so we call it trigonal pyramidal okay what if two of the what if two of the um the bonding pair are replaced by the lone pair electrons then it forms the structure like water so H2O okay so oxygen has two single bonds it also has two lone pairs of the electrons so in total the central atom oxygen has one two three four four electron pairs so again it's electron domain geometry is tetrahedral but when we actually refer to the three-dimensional shape or the geometry of the water we only refer to we're only talking about the uh the bond pair the bonding pair so it has the bent shape next will be MX-5 the central atom um has five of the electron pairs on pcl5 phosphorus pentachloride okay so this is interesting structure so um with Center atom and and then with five um um electron pairs surrounding it two of the electron pair will go up and down so they're in one one straight line they're in the vertical line and then the other three are 120 degree away from each other and they are on this horizontal plane perpendicular perpendicular to this the vertical line so this is the horizontal horizontal surface and then um right into thinner we have the phosphorus and then um one chlorine and then two chlorine and then the third chlorine and then up and down two more chlorine okay um so these three bonds are 120 degree away from each other and in these two bonds or these two bonds they are 90 degree away from each other and we call this trigonal bipyramidal because it has the base of a triangle and then it looks like a pyramidal but there are two pyramidal one is of and one is down so we call it trigonal bipyramidal what if one of these five um bonding pair is replaced by a lone pair electron okay then it's going to form that um then okay then uh one of these three Bond pair will be replaced by the lone pair electron okay and then you will have the shape of the sea salt okay next what if two of these five Bond pair um are replaced by Electro by lone pair then they're going to form this T shape again up and down x x and um on this horizontal surface it's going to be an electron pair electron pair and then um right so it eventually it's going to be t-shaped what if um what if um three of this five Bond pairs are replaced by the lone pair of electrons then it's going to form this linear shape so such as Tri iodide I3 minus um so um one two three these three electron pairs on um on one single surface there are lumpier electrons then when it comes to molecular geometry we only consider the bond pair these two which are opposite to each other so it has the linear shape the next the very last one is Ms MX6 um when the center atom is surrounded by six electron pairs um this is actually kind of rare So as F6 is one of the only examples and then it has um and then and this means that um this denture atom will have two electron two electron pairs on left and right and front and back up and down so all of these electron pairs are 90 degree away from each other and then um that's why we call it okay hedral if one of this Bond pair is replaced by lump here then we have this a square pyramidal shape and if two of the electron pairs are replaced by lumpier electrons then they have the square planar shape you will have to memorize the name of all of the molecular molecular geometry okay so now here is a review of or comparison between the Lewis diagram electron domain geometry and molecular geometry so always remember that when we refer to the three-dimensional shape or just a shape or structure of a molecule we're always referring to the molecular geometry okay so let's say for example water H2O it's the Lewis Dot Diagram will be a hydrogen oxygen single Bond oxygen hydrogen single Bond and then four electron four lone pair electrons than the oxygen so for the Lewis Dot Diagram it doesn't really matter how you draw it you can draw it as a linear structure you can draw it at the back structure both are considered correct in Lewis diagram because the Lewis diagram only cares about the atom Arrangement so how is hydrogen bonding to oxygen is in a single Bond or double bond that's the oxygen carries the lumpier electrons is a hydrogen hydrogen oxygen or hydrogen oxygen hydrogen these are Del and these are solved in Lewis diagram and then based on the Lewis diagram you are going to draw the electron domain geometry which minimize the electron electron reposition in three-dimensional shape so um um including the lone pair electron the oxygen is surrounded by one one two three four so it's electron domain geometry is tetrahedral um so it has oxygen um and um the oxygen hydrogen hydrogen and then lumper electrons and lump here electrons tetrahedral and when it comes to molecular geometry I only considered the bonding pair or the atoms so I'll need these parts are considered then it will be the bent shape or the bent molecular geometry okay next based on the Lewis diagram for NH3 um shown above the H and H Bond angle is closest to which of the following so NH3 so n nitrogen is the central atom and then it has one two three four four electron pair including the lone pair so it's electron domain geometry will be tetrahedral nitrogen um okay up and then the tripod okay so um hydrogen hydrogen hydrogen lumpier electrons okay and um the bond angle of tetrahedral is 109.5 degrees so the answer is C okay next let's try to compare polar versus nonpolar molecule so now we know um because we learned a vast birth we notice three-dimensional structure of a molecule or the shape of a molecule and based on the three-dimensional shape we can determine if a molecule is polar or not polar so there are two criteria that we take a look at the first one is molecular geometry the three-dimensional shape and then the second one will be the end of visual Bond okay so for molecular geometry um if on the if um if it has a symmetry molecular geometry then it is already polar molecule so let's say for example um let's say t-shaped if a molecule has t-shaped so um let's say the center atom is M and then um it has other atoms attached to it up and down and then um one more want more and then on the left side it has the lone pair electron so this is the C cell structure um okay um so this is already um a symmetric in in three dimension in 3D then I don't even have to um pay attention to the bond this is just a polar a polar uh polar molecule obviously this is polar obviously um or let's say bent on M X okay um as for the band The symmetric um ask for the band structure and this is asymmetric um already so I don't even have to consider what type of bonds it is this will be just polar bonds okay so what if it is a symmetric structure such as tetriserial so then I need to take a look at all of the bonds so for example I have a structure of ccl2h2 okay so it has the tetrahedral um shape but two of the bonds will be carbon chlorine bonds and two of the bonds will be carbon hydrogen bugs and carbon chlorine bond is polar and carbon hydrogen bond is nonpolar and these four bonds do not cancel on each other they are not balanced so this will be polar for sure and let's say um Boron um dihydride and Boron dihydride and chloride so Boron surrounded by one chlorate and then two hydrogen so it has this perfectly symmetric 120 120 120 trigonal planar structure but because the bonds are not exactly the same so this is still a non-symmetric asymmetric structure and this will be considered polar next which of the following Lewis Dot Diagram represent a molecule that is polar um okay so um so a BF3 so it has the the central atom boron has one two three um three um three electron pair so boron fluorine fluorine fluorine it's perfectly symmetric trigonometer and then each of the bond is exactly the same so it is perfectly symmetric this is um this is non-polar and B carbon dioxide the central carbon has one two two electron pair um so it it's going to form that linear structure and um each of the bonds are the same so it is going to be nonpolar as well and then the next it will be C okay so this is the example that I made a ccl2h2 so the structure the three dimensional geometry itself is um is is symmetric but um because um four of the bonds are not exactly the same so it is polar and what about D nitrogen nitrogen gas okay so it's nitrogen nitrogen triple bonds and then this is the linear structure and then um two atoms are exactly the same it's even a non-polar covalent bond um it's um perfectly balanced perfectly symmetry so it's non-polar obviously okay so what is hybridization um so hybridization is the mixture or Fusion of orbitals um of different energy stop shells to form new orbitals with the same energy level okay so what I mean by that is let's say s orbital and p orbital they have different energy levels this is 2s and this is 2p and when they combine together they're going to form this let's say sp3 orbital and then their energy level will be in between s and p orbital so this is what I mean by hybridization but you guys are not required to know what it forms or um or about the exact energy levels of the newly formed sp3 orbitals you will only be tested on the types of the hybridization so um when the number of the electron pair so when I say again one is the electron pair it includes cells the lone pair and then the bonding pair when number of the electron pair is equal to two then it is sp hybridization when it's three electron period then it's SP2 hybridization when number of the electron pairs around the central atom it's four then it forms as CS3 hybridization this is the only thing that you need to know for AP Chemistry exam okay so let's let's try to do this frq question um answer the following questions about nitrogen gas and about um the hydrogen and the box below draw to complete Lewis electron dot diagram of nitrogen N2 okay again two nitrogen atoms means two times five in total so 10 valence electrons that's what we are given to achieve the full octet State 2 times 18 we need 16 electrons for we need six electrons so we are six electrons short which means six electrons are shared within this nitrogen yes um molecular structure okay so it will be nitrogen nitrogen one two three one two three and each of the nitrogen will have a minus six which is equal to two lone pair electrons okay so you can either drill this or you can draw nitrogen triple bond nitrogen with two lone pair electrons B based on the Lewis electron dot diagram that you drew is the nitrogen molecule polar no it is nonpolar explain because it is a linear shape um with um non-polar covalent bonds and it is perfectly symmetric next the following graph shows the potential energy of the two nitrogen atoms versus distance between their nuclei on the graph indicate the distance that corresponds to the bond lengths of nitrogen molecules by placing an x on the horizontal axis okay so for these type of questions I told you that you always look for that on the peak of this potential graph which is the lowest potential of energy okay so this um the the distance corresponding to this peak will be um the the bond length for the nitrogen nitrogen Bond on the graph which shows the potential energy curves of two nitrogen atoms carefully sketch the curve that corresponds to the potential energy of two oxygen atoms versus the distance between their nuclei okay so for the nitrogen um yes so um in between um in within the nitrogen uh nitrogen molecule nitrogen forms nitrogen nitrogen triple bonds while oxygen forms oxygen oxygen double bonds and then we know that triple bond is um triple bond is shorter and is stronger than the double bonds okay which means the potential energy for the oxygen will be higher because it's not as stable or it's not as strong as the triple bond of the nitrogen and also it is going to be a little bit longer than the nitrogen nitrogen triple bond so the peak of this oxygen oxygen um oxygen oxygen bonds will be higher and on towards the right side of the peak of the nitrogen nitrogen bonds so this is how the oxygen oxygen bonds look next the Lewis electron dot diagram of the hydrazine is shown Below based on the Lewis electron diagram of nitrogen and hydrogen compare the length of the nitrogen to nitrogen bond in nitrogen where the length of the nitrogen nitrogen bond in the hydrogen okay so again nitrogen nitrogen triple bond in N2 and then nitrogen nitrogen single bond in hydrogen and obviously the triple bond is stronger and shorter than the single Bond so nitrogen to nitrogen Bond in in two is shorter and next compare the strings okay then it is stronger and the last one identified a hyper edition of nitrogen atoms and hydrogen in the hydrogen the nitrogen atom has one two three four four electron pair so it has sp3 hybridization this is it for unit two