in this lesson we're going to talk about ionic bonds covalent bonds particularly in polar covalent bonds and nonpolar covalent bonds so let's say if we have this bond the bond between two hydrogen atoms would you describe this bond as ionic polar covalent or nonpolar covalent anytime you have a bond between two atoms of the same element it's always going to be a nonpolar covalent bond now the reason why it's a covalent bond is because the electrons in this bond are shared equally due to the fact that we have the same atom I mean the same type of atom and so therefore they have the same electronegativity and so they pull on those electrons with an equal force so because the electrons are shared equally in this molecule it's going to be a nonpolar covalent bond that has another example for you what about the carbon oxygen bond would you describe it as ionic or covalent now anytime you have a bond between two nonmetals typically it's usually a covalent bond so we need to determine if it's a polar covalent bond or a nonpolar covalent bonds and we need to look at the electronegativity values of these two elements so here are some numbers that you want to be familiar with hydrogen has an electronegativity value of 2.1 boron is about let me list out the elements boron a carbon nitrogen oxygen and fluorine so boron is about 2.0 carbon is 2.5 and is 3.00 is 3.5 F is 4.0 and these values are based on the textbook I'm using some textbooks might have slightly different values but you want to use the values based on a textbook you're using so carbon has an electronegativity value of 2.5 and oxygen has a value of 3.5 if the electronegativity difference is 0.5 or more than the bond is said to be polar if the electronegativity difference is 0.4 or less then the bond is said to be non polar so three point five minus two point five that's one so therefore we can say that the carbon oxygen bond is a polar covalent bond the electrons are being shared but not equally now because oxygen is more electronegative than carbon it's going to have a partial negative charge and carbon because it's less electronegative in oxygen it has a partial positive charge so how can we indicate bond polarity how can we show the dipole moment in this bond you need to draw an arrow pointing towards the more electronegative element and so whenever you see a dipole moment like this it tells you that this bond is a polar bond now what about the bond between sodium and chlorine would you describe it as ionic polar covalent or nonpolar covalent sodium is a metal chlorine is a nonmetal and typically when you have a metal mixed with a nonmetal for the most part it's safe to say that it's going to be an ionic bond sodium chloride is made up of ions in this substance sodium has a positive charge and chlorine has a negative charge positively charged ions and known as cat ions and negatively charged ions are known as anions and so that's why we have an ionic bond you know that opposite charges attract and so there is an electrostatic force of attraction that keeps these ions held together and that makes the ionic bond so typically whenever you have a metal mixed with a nonmetal ionic interactions are usually created now it's important to understand the difference between an ionic bond and a covalent bond in a covalent bond the electrons are shared in an ionic bond the electrons are transferred so in a polar covalent bond they're shared unequally but in a nonpolar covalent bond the electrons are shared equally sodium has 11 electrons but it has 1 valence electron chlorine has 7 valence electrons so when you put together let me draw this differently an atom of chlorine and sodium sodium it's going to give away its one valence electron to chlorine and when it loses that electron it acquires a positive charge when chlorine accepts it it's going to have eight valence electrons and so it's going to be negatively charged since it gained an extra electron so after this transfer of electrons there's going to be an electrostatic force of attraction that holds these ions and so that makes up the ionic bond now let's talk about the hydrogen atoms that make up the h2 bond let's say if we have two individual atomic hydrogen particles both of which contain one valence electron when these two get together they will each give up their valence electron to form a covalent bond and so the two electrons represented by that bond are shared equally among those hydrogen atoms and that's why it's a nonpolar covalent bond the electrons are shared in the ionic bond you had a transfer of electrons sodium gave up an electron chlorine accepted it but here both hydrogen atoms contributed an electron to create this covalent bond and so that's why it's not ionic but it's covalent you have a sharing of electrons as opposed to a transfer of electrons now let's go through some more examples so what about the carbon hydrogen bond would you describe it as ionic polar covalent or nonpolar covalent now carbon has an electronegativity value of 2.5 and for hydrogen's 2.1 so the electronegativity difference is point 4 which means that this bond is nonpolar whenever you see a molecule that contains only carbon and hydrogen bonds it's a nonpolar molecule for example methane is nonpolar it doesn't mix with water or hexane c6 h-12 that's a non-polar molecule they don't dissolve in polar substances like water or like alcohol now what about the carbon-carbon bond is the ionic or is a covalent now both substances have the same electronegativity value so the en difference is zero which means that it's nonpolar so anytime you have two of the same type of atoms that make up a bond it's always going to be a non-polar bond the electrons will be shared equally now what about the Oh H bond what can we say about is it an ionic bond a polar covalent bond or a non polar covalent bond well let's start with the electronegativity values oxygen has an electronegativity of 3.5 and for hydrogen it's 2.1 so the electronegativity difference is 1.4 so this bond is highly polar now it's a special type of polar bond anytime you see hydrogen directly attached with nitrogen oxygen or fluorine it's a special type of bond do you remember what it is it's known as hydrogen bonding these are very powerful in some local forces because of hydrogen bond in water has a very high boiling point for being a molecule most molecules have low boiling points but those with hydrogen bonds they have relatively high boiling points so we have a polar covalent bond with a special case of hydrogen bonding now let's indicate the bond polarity because the oxygen is more electronegative it's gonna have the partial negative charge and hydrogen is going to have the partial positive charge so to indicate the dipole moment we're going to draw the arrow towards the more electronegative element now let's consider one more example what about the bond between lithium and fluorine would you say it's an ionic bond a covalent bond and if it's covalent is it polar covalent or nonpolar covalent lithium is a metal fluorine is a nonmetal so automatically just by identifying the type of element that we're dealing with we know it's going to be an ionic bond the electronegativity difference between lithium and fluorine is huge but for the most part if you have a metal and a nonmetal it's safe to say that you have an ionic interaction the lithium is a positively charged cation and fluoride is a negatively charged anti