Covalent Bonding Part 1

追加: 2026-05-11

[00:00:03]all right guys so let's do a quick recap from yesterday um we went over finding valence electrons drawing dot structures for atoms ions and ionic compounds um so here we're going to draw the dot structures for barium the barium ion chlorine the chloride ion and magnesium nitride um so looking at this barium that is given does not have a charge so remember we need to find its location on the periodic table it is in the second column meaning that it has two valence electrons it's in that group 2A so remember we're going to draw the two valence electrons around the atom but remember we cannot pair them yet until there are at least four around that atom where the barium ion which it tells you is a positive two charge and remember the charge can be found kind of by the column as well that means that since it's a positive 2 it means it lost two electrons so this is our Dot Structure where it is empty and has lost those two valence electrons for chlorine it is number 17 on the periodic table it's in that group 7A so it has seven valence electrons that will be drawn around the atom for the chloride ion remember the negative charge means that it gains an electron these want to be full and have that full octet so this will have all eight electrons around it and you may see it with or without brackets last one is the magnesium nitride the mg3n2 and that means that we have three magnesiums and two nitrogens magnesium is in the second column on the periodic table so it has two valence electrons on each of these nitrogen is in group 5A so each of these has five valence electrons so remember this has a metal and a non-metal so it is an ionic compound ionic compounds we represent showing that transfer of electrons remember all the metals are trying to become empty where that inner layer of valence electrons is full whereas the nitrogens the non-metals are trying to get that full octet to be full with eight so magnesium will give two electrons that first nitrogen magnesium is now empty but nitrogen only has seven electrons now so it needs one more so it'll take one from a second magnesium now that nitrogen is full but magnesium still has one electron to get rid of so that's where a second nitrogen comes in it'll give that extra electrons in nitrogen so now that second magnesium is empty but now that second nitrogen only has six electrons which is where a third magnesium comes in to give up its two electrons so now all three magnesiums are empty and both nitrogens are full with eight so remember this showing the arrows and the electron transfer is the complete Dot Structure for magnesium nitride all right guys let's switch over to our notes and today we're going to focus on those molecular covalent compounds um so with molecular compounds they are going to be held together with a covalent bond a covalent bond is an attraction between atoms that are sharing electrons so whereas ionic had a transfer of electrons covalent is going to be sharing those electrons to where they belong to both atoms that are attached these are going to make up a molecule a molecule is an electrically neutral group of atoms that are held together with those covalent bonds so by sharing electrons we do have some substances that are considered diatomic molecules and these are molecules that are made up of two atoms so dye means two these are things that do not exist in nature as a single atom now you're never found by themselves they always have to have a partner the diatomic molecules you do need to be aware of and you'll see these there are a couple ways to remember them one way is the anagram brinkelhoff so brinkelhoff the seven diatomic molecules are bromine iodine nitrogen chlorine hydrogen oxygen fluorine all of those are never found by themselves in nature so like oxygen that we breathe is O2 because you're never going to have an oxygen floating around by itself another way to remember these is there are seven of them they're the dynamic seven on the periodic table if you start at number seven on the periodic table nitrogen and actually draw a seven with your finger that goes through nitrogen oxygen fluorine chlorine bromine and I'm going to leave myself enough space iodine that is six of the seven and don't forget hydrogen is kind of off by itself so those are two ways to remember the seven diatomic molecules and we're going to be using those several times throughout this unit a molecular compound is a compound composed of molecules so composed of only non-metals so remember ionic was a metal and a non-metal molecular compounds are only non-metals and molecular compounds sorry guys molecular compounds tend to have low melting points and boiling points whereas ionic metallics have tried all right so I said ionic compounds had the high melting points and boiling points they tended to be solids at room temperature whereas molecular compounds have lower melting points than boiling points so majority of these are actually gases at room temperature with a few exceptions that are liquid we're looking at properties of our covalent compounds or molecular compounds like I said they have low melting points and boiling points they have very poor electrical conductivity and they actually tend to not conduct electricity in general or heat and so these tend to be used as like insulation in houses and things like that and molecular compounds tend to have a polar nature we're going to talk about that more at the end of the unit um but it just means that even though electrons are being shared they may not be shared equally so with molecular compounds they are written out with this molecular chemical formulas so the chemical formula shows the kinds and number of atoms present in a molecule of a compound so the formula tells you which elements are involved and how many atoms of each element you have so for example water everyone knows water is H2O that means it has two hydrogens and one oxygen always so this tells you how many of each atom you have but it doesn't tell you how they bond together it doesn't tell you do the two hydrogens attach to each other or do the two hydrogens attach to the oxygen so that's where we use diagrams or dot structures to look at the arrangement of atoms to look at how these bond together so with covalent bonding when forming covalent bonds electron sharing occurs the atoms with the shared electrons included have that full octet so remember everything is trying to have eight total valence electrons which is the same as a noble gas the exception is hydrogen helium remember can only have up to two total electrons so everything is trying to have eight with the exception of hydrogen when we're bonding and in a compound atoms will share electrons until every atom has a complete octet so the electrons do not have to stay on their original atom um so like we said covalent compound they will share enough for everything to have eight whereas ionic they transferred enough electrons for everything to have eight excuse me I hit an extra button so first thing that's going to form is a single covalent bond this is the most common one we come across this is where two atoms are going to be held together by sharing a single pair of electrons is going to be considered a single covalent bond this is how a lot of our diatomic molecules are held together so diatomic molecules are all sharing electrons the diatomic molecules that are single covalently bonded together are hydrogen and our halogens so remember that's that group 7A and any electrons that we have that are not shared by the atoms are referred to as unshared pairs of electrons so those will be represented as dots so just to show you what this looks like kind of simplified so remember hydrogen is H2 hydrogen has one valence electron they simply share their one valence electrons that they both have access to two with our halogens I'll pick fluorine because that's the one that's at the top so fluorine is F2 each fluorine has seven valence electrons so what they'll do is they will share that one that way they both have eight whenever you're including that Bond so anytime you see a bond that is representing two electrons and like you can see on fluorine those dots around the fluorine those are those unshared pairs of electrons we were referring to okay so the single covalent bond build the octet for those particular molecules well if sharing one pair of electrons doesn't fill the octet we can also form double and triple bonds so atoms will form double or triple bonds if they cannot attain a full octet by sharing only one pair of electrons so they will continue sharing until the atoms are full um in a double bond this forms between atoms that share two pairs of electrons so that will have a bond with two lines which remember each line was two electrons this will represent four electrons a diatomic that's held together by a double bond is oxygen so oxygen has six valence electrons so whenever it shares one pair of electrons that's only seven valence electrons so it would need a have a second pair shared so you'll see this kind of cleaned up where you have that double bond in the middle um if they still do not have a full octet a triple bond can form so triple bonds will form between atoms that share three pairs of electrons so Each Bond is two electrons so we'll share a total of six electrons this if we look at nitrogen each nitrogen has five valence electrons if they share one they only have access to six when they share a second pair they both only have access to seven so they have to share a third pair and I'll clean that up a little bit so they will share a third pair of electrons that way both nitrogens have access to eight so all of our diatomic molecules are held together with covalent bonds like you said hydrogen the halogens are single bonded oxygen has to be double bonded nitrogen has to be triple bonded and the atoms become closer together with an increased number of bonds holding them together so single bonds are rather long in comparison to the other ones when a double bond is formed it cuts that space in half essentially and the atoms are now closer together when there is a triple bond it pulls those atoms even closer together and in general the more bonds there are the stronger they are so it's the higher the energy is needed to break those bonds so as you increase the number of bonds the length of the bond gets shorter but it also gets stronger it's going to be harder to break when there are multiple bonds there all right guys so just to summarize um a single Bond we said is sharing two electrons this is always the first one that forms it is the longest and therefore the weakest a double bond can form next if needed that shares a total of four electrons and it gets a little bit stronger but also a little bit shorter whereas a triple bond is the shortest of the three that's sharing a total of six electrons and it is the strongest um I'm gonna have to stop here to take care of the baby um and I will record a part two going over drawing these dot structures um molecular dot structures are the more common ones we tend to draw um so make sure to check back for part two thank you