chapter 5 Part B molecules and compounds learning objectives in this part we will discuss molecular or covalent compounds here we are going to give her another one time the definition of molecular or covalent compounds we are going to see how we write molecular compounds and then how we name combat provided or molecular compounds I'm sorry let's see the definition in a couple of examples covalent bonds or covalent compounds covalent bonds are formed when atoms share electrons in a relative here it's a stable electron configuration but we haven't discussed electron configuration I'm going to say they share electrons in order to achieve a stable number of electrons that's something that we will be able to discuss later on so they form when nonmetals are coming together and basically nonmetals are at the group 4 a 5 a 6 a 7 a and hydrogen that it's at 1 a let's see a couple of examples chlorine for example has 17 electrons it is unstable if it was possible to have a 18 electrons like argon next to it then it will have been stable see what's happening these two atoms are coming together this chlorine provides one electron and now the other chlorine provides another one electron and they place these two electrons at the overlapping area so these two electrons belong to this atom and to this atom by doing so this chlorine has 16 plus 2 18 electrons and this fluorine has 16 plus 2 18 electron the stable like our would like to be at home next to it this bond here is called a covalent bond because neither atom is losing an electron or gains an electron but rather they are sharing an electron so covalent bonds are about saving one pair or more this is the chlorine molecule basically the chlorine molecule consists of two chlorine atoms here it is since they serve only one electron pair this is a single bond between the chlorine that's why we are using this line this dashed line between the two chlorine atoms in order to symbolize the bone that we have between mr. oxygens eight and eight the yellin stable look at the periodic table neon with ten electrons is stable so if there was a way for each one to gain two electrons then they will be stable too so this oxygen contributes two electrons and this oxygen contributes two electrons they are coming close to each other so they have an overlapping area that you're placing these four electrons in the overlapping area now this oxygen has 6 plus 4 10 and this oxygen has 6 plus 4 10 electrons so they are stable like Neil right and that's how symbolized the molecular oxygen the oxygen molecule oxygen with another one oxygen are coming together in order to form something stable they serve two pairs of electrons so much why we have two lines between them we write it as all two and we say the molecular oxygen in the oxygen molecule we have a double bond between the two oxygens another one nitrogen its nitrogen has seven electrons if they could have ten each one then they will be stable right see what's happening they're coming together and be assured three pairs so four plus three four plus three so this one contributes reselect three electrons and this nitrogen contributes three so they share three pairs another stable like neon we write that the nitrogen is connected with the other nitrogen in the nitrogen molecule and they are connected with a triple bond writing and naming molecular compound when you write a molecular compound or a covalent compound first you write the element that it's farther away from the fluorine and then you write the one that it's closer to the fluorine for example they let you know that we have a covalent compound or a molecular compound that consists of five chlorine atoms and one phosphorus atom well the fluorine atom Aksum is here and the chlorine is here so first I will write the one that is farther away the phosphorus and then I will write the chlorine remember when we were talking about iron compounds that we said that we are crossing the charges and then we can find the subscript with covalent compounds is different because we do not have charges here so when it comes to covalent compounds or molecular compounds they need to let us know how many atoms from its element you have unit for example they let us know that we have five chlorine and one phosphorus so I write first the phosphorous I don't have a subscript here h1 basically and as far as the chlorine is concerned I have five chlorines and that has nothing to do with the charge of the phosphorous because in covalent compounds the atoms we do not have a charge here's the compound pcl5 and we will learn how we name it let's see another one compound contains three bromine and iodine well the one that it's farther away it's the iodine that's going to go first the one that is going to go second is the bromine that is closer to the fury so the compound is i BR three we have one iodine atom so we don't need a subscript here we have three bro means so we have a three over there now the wrong example we have a covalent compound or molecular compound that consists of torques since one carbon here is the carbon here is the oxygen this is going to be second this is going to be first so the compound is sealed the name now we named first the first element as it is and then the second one has the idea and so this is hydrogen chloride if we have more than one than we need to put in front of it to the prefix one die tri tetra penta hexa four six five four four four three eight etcetera you need to memorize this so this compound is going to be phosphorus pentachloride let's a couple more examples hydrogen bromide died chlorine oxide or die chlorine monoxide next one died nitrogen tetroxide nitrogen trifluoride let me make the parenthesis here do you remember this one here we said dichlorine monoxide or oxide so after the second element you may or may not put the prefix Mon so this risk could be dichlorine monoxide or die chlorine oxide the same thing here however in front of the first element we never put the prefix Mon so the mono nitrogen trifluoride will have been incorrect here we have to say nitrogen trifluoride let's say this exercise we have to write the chemical formula for the following but like little covalent compounds I want you to take the time to answer the problem by yourself and then come back and we are going to see the answers together welcome back first compound contains two oxygen atoms at one nitrogen atom well the oxygen is closer to the fluorine right so we are going to write it second the nitrogen is farther away so we are going to write it first they let us know that we have two oxygen atoms so we have it two here and we have only one nitrogen so no subscript what's the name nitrogen dioxide next one one phosphorus trichloride atoms the chlorine is closer to the fluorine right so it's going to go second so phosphorus one chlorine three can you tell with the name phosphorus tri chloride next one one iodine and three chlorines which one is closer to the chlorine the chlorine so it's going to go second I CL three the name are you dying tri chloride another one one oxygen one Calgon which one is closer to the fluorine oxygen and that's the one is going to go second so the name carport either oxide or monoxide so carbon oxide or carbon monoxide another one one oxygen to flow rates hmm which one are we going to write second definitely the chlorine here we go and the name oxygen dye flow right another wrong problem we have to give the name now for the following molecular or covalent compounds try to do it by yourself and we are going to say together first one silicon tetrachloride next time die phosphorus and oxide okay this one here can be pentoxide or panda oxide same thing next one die chlorine hepta oxide restaurant will be heptoxide or head topside either I'm so but between the teeth yo you may or may not have any next one we have the name and we need to write the formal of the covalent compound or molecular compound so pause the presentation and try to answer the problem by yourself welcome back phosphorus pentachloride 1 phosphorus 5 chlorine here we go next time dinitrogen trioxide so two nitrogen's three oxygens next time so for hexafluoride one sulfur hex six fluorine atoms here is the phone next time we have to identify whether it's a covalent or I only compound and then to give the correct name try to do it by yourself and then come back again the first part I only call covalent well non metal nonmetal so it is a covalent or a molecular compound what's the name for this sulfur dioxide next one ionic or covalent well we have a nonmetal and we have we have sorry a metal and a nonmetal this is a main element so easier it's an ionic name barium chloride here well here we have a medal and here we have a polyatomic anion between the phosphorus and the oxygen we have a covalent bond but then here we have an ionic bond so this is an ionic compound named calcium we have to memorize this right it's a phosphate for spite we'll have three oxygens calcium is a main element so we don't really need to give the charge next one ionic or covalent well copper is say metal is a transition element transition metal so this is going to be an ionic compound name well this is a transition element so we need to give the charge with the charges this is to - I see that - so this one must have plus one otherwise I will need the parentheses here and this is copper one carbonate the next one the last one here we go the last one is a non metal nonmetal so it's a covalent compound the name is going to be die nitrogen tetroxide or tetroxide here we go at this point we have finished with it's after 5:00 half-baked we discussed molecular compound and we saw the definition for another one time and a couple of examples and we discuss extensively how we write molecular or covalent compounds and then how we name them to forget attention I will see you shortly with chapter 5 Part C they will discuss about acids and we are going to close chapter 5 by discussing formula much