Ionic and Covalent Bonding - Chemistry

Consider this problem, what type of bonds are contained in the following substances? Is it

ionic

or

covalent

? And if it is

covalent

, would you describe it as polar covalent or nonpolar covalent? Now, before tackling this problem, we need to be able to determine the difference between an

ionic

bond and a covalent bond so how can we quickly distinguish the two? Let's say if we are given a test problem, the first thing I recommend knowing is that an ionic bond is usually found between a metal and a non-metal. Covalent bonds generally exist between two non-metals and within an ionic bond an ionic bond occurs between ions and ions are particles that contain positive and negative charges covalent bonds basically have partial charges if it is polar covalent if it is non-polar covalent then those charges are minimal now the second thing that What you need to keep in mind is that covalent bonds involve sharing electrons, while ionic bonds are created through a transfer of electrons and later in this video I will explain these concepts, but let's see if we have enough information to answer this. particular question so let's understand part a or answer br2 what kind of bonds are contained in that substance then br2 is bromine and it looks like this then you have a molecule which is made up of multiple atoms in this case this molecule has two atoms and within This molecule has a single bond and each atom has three free pairs, this is what the bromine molecule looks like, but now let's describe the bond that holds these two atoms together, is it ionic or covalent?

So do we have two non-metals or is it this one? a metal mixed with a non-metal, you need to know where metals and non-metals are on the periodic table to answer that question first, so let's take a minute and talk about that, so if you're going to look up your periodic table or if you don't have one go to google images and search for the following elements, they should be at the top right of the periodic table and you will see this line dividing some of these elements, now most of the elements. Those located near that line are known as metalloids or semiconductors.

A metalloid has properties that fall between a metal and a non-metal, but what must be deduced from this is that non-metals are located to the right of that line and to the left of that line. has the metals, so by using the periodic table you can quickly determine if an element is considered a metal, a non-metal, or if it is in a line, a metalloid, so bromine is on the right side of the periodic table Therefore, bromine is considered a nonmetal. -metal, so here we have two non-metals mixed together and because those elements are the same, the two electrons that are in this bond will be shared equally between those two atoms, so we will have a covalent bond, so at any time there is some type. of sharing electrons you have a covalent bond now that we have a covalent bond we have to discuss whether it is a polar covalent bond or it is a non-polar covalent bond in a non-polar covalent bond the electrons are shared equally if it is polar covalent, that means that the Electrons are shared between the two atoms but relatively unequally, so in this case this will be a non-polar covalent bond because the elements are the same for it to be a polar covalent bond the elements have to be different, so let me give you some notes on this, so if it's going to be polar covalent, the electronegativity difference has to be 0.5 or more.

A non-polar covalent bond has an electronegativity difference value of 0.4 or less, so keep that in mind now, let's consider. methane ch4 here is the Lewis structure of methane and we are going to focus on the hydrogen bond of carbon, so is this particular bond ionic or covalent, what would you say? Let's compare that bond with the bond between two hydrogen atoms now automatically if the elements are the same in a chemical bond then you know it will be a non-polar covalent bond but if the elements are different it could be ionic or it could be polar covalent or it could even be non-polar covalent, but first let's see if it is ionic or covalent, so carbon is a metal or a non-metal.

What would you say carbon is considered a non-metal? It's on the right side of that line. Hydrogen, although on the left side, is not actually considered. to be a metal it is considered a non-metal so be careful with that, here we have two non-metals combined so we know this is a covalent bond. Now, is it polar covalent or non-polar covalent? Answer that because the atoms in that bond are different, we need to look at the electronegativity values. Here are some common values ​​you want to be familiar with. The electronegativity value for hydrogen is 2.1, for boron it is 2.0 for carbon 2.5.

Nitrogen is 3.0 and then oxygen is 3.5. Fluoride is 4.0. is the highest and then we have chlorine which is 3.0 bromine 2.8 iodine 2.5 and you can look up these values ​​if you go to Google Images and type in the electronegativity values ​​it should appear so in the link ch the electronegativity difference between the two elements be 2.5 minus 2.1 which is 0.4 therefore the bond is considered non-polar if the elements are same then the difference in will be zero which means definitely is nonpolar, so both bonds are nonpolar covalent bonds. Now let's move on to part c. What type of bond do we have between the elements carbon and oxygen?

What would you say? Is it ionic or covalent? Well, carbon is a non-metal and oxygen is a non-metal, so we have two non-metals, which means the bond between them is rather covalent. than ionic Now to determine if it is polar or non-polar, we must look at the electronegativity values. Carbon has an en value of 2.5 and oxygen is 3.5, so the difference in electronegativity between the two elements is 1.0, which is greater than 25, so this particular bond is a polar covalent and that's basically it, that's how you can quickly tell if it's polar covalent or non-polar covalent and that's by looking at the difference values.

Now let's move on to lithium fluoride, is it ionic or covalent? Well, lithium is activated. the left side of the periodic table, so it is a metal, in fact, it is an alkali metal. Fluorine is on the right side of the table, it's a halogen, which is a type of non-metal, so here we have a metal and a non-metal, when you see that. tells you that you are dealing with an ionic bond now let's delve into ionic and covalent bonds, let's understand how they are formed now let's start with ionic bonds before going back to covalent bonds lithium as an atom has one valence electron fluorine as an atom has seven electrons of valence, fluorine as a non-metal has a very high electronegativity value, it is 4.0 and lithium as a metal has a very low electronegativity value, I don't remember what the number is, but it could be 1.0 or less, but is pretty. low and because fluorine is more electronegative it has a strong affinity for electrons you really want it and halogens like to have eight electrons to satisfy the octet requirement they want eight electrons in their outer energy level to be stable for be satisfied and so what?

What you need to understand is that metals like to give up electrons and non-metals like to take them, so what's going to happen here is that we're going to have an electron transfer, so lithium is going to give up its electron to fluorine. and then, when lithium loses that electron, it will acquire a positive charge, when fluorine gains that electron, it acquires a negative charge. Now, what do you know about opposite charges? If you have a positive charge next to, say, a negative charge, what will happen to both? get it right, opposite charges attract, so you will have a force of attraction and this force keeps them together, so this is the chemical bond between these two ions, it is called an ionic bond, so the electrostatic force of attraction It is what maintains ionic bonds.

Together now let's consider the situation in a covalent bond and use bromine as an example, so bromine as an atom has seven valence electrons like fluorine and because they are in the same column of group seven a of the periodic table, both They are halogens and as a result, they both want eight electrons when a bromine atom meets, say, another bromine atom. They both want to have eight electrons, but neither wants to give up their electrons, so they say: how are we going to do it? solve the situation I need an extra electron and you need an extra electron what kind of deal can we make so that we both get what we want in this case what they do is share electrons and then the bromine gives up an electron to form a bond and the other atom of bromine also gives up one electron and note that it takes two electrons to form a bond so we get the bromine molecule that looks like this and there is a single bond between them so each bromine atom now has eight . electrons around it, so if we look at the bromine atom on the left two four six and this is considered two, so that's eight electrons, the same goes for the one on the right, it has two four six and the two shared electrons , so he has eight. and in this arrangement they satisfy the octet requirement that they have, that is, having eight electrons in their outermost energy level.

Now, because the electronegativity of the two atoms in this molecule is the same, the electrons are shared equally, so this will be a non-polar covalent bond now let's talk about the other situation, a polar covalent bond and in this video we use the example of carbon and oxygen, so carbon as an atom has four valence electrons, oxygen as an atom has six valence electrons, now both of them are non-metals and as a result they want to acquire electrons so like in the previous example They need to make a deal they need to share electrons so they can both have eight the question is how are they going to do it in this case they are going to share electrons unequally for this to work carbon will give two electrons to form a bond between carbon and oxygen , but oxygen will give four electrons, so we have a total of six shared electrons and, if you remember, two shared electrons are needed. to make a bond, then six electrons will form a triple bond.

The Lewis structure between carbon and oxygen looks like this, so those are the six electrons that were used to make that bond, so carbon gave up two, meaning it has two oxygen electrons left. he gave up four, which means he also has two left, so this is the Lewis structure for carbon monoxide, carbon has an electronegativity value of 2.5 and oxygen is 3.5 and as the Oxygen is more electronegative than carbon, it will attract the electrons from that bond. closer to itself, so oxygen will take on a partial negative charge, which is why it has this delta-looking symbol for partial charges, and, uh, carbon, because it has a lower electronegativity value relative to oxygen. , will lose some electrons to oxygen.

The oxygen will attract them. electrons closer to itself, both still share electrons, but what we have is an unequal exchange of electrons and because of this unequal exchange, one element attracts electrons more than the other and because oxygen has a greater attraction, it goes have a partial negative charge, while carbon will have a partial positive charge and when you have these partial charges on a covalent bond, it becomes a polar covalent bond. When something is polar, it means that it is still neutral overall, but is polarized on one side. it has a partial positive charge and the other side has a partial negative charge and that's what it means that something is polarized, you have a charge separation in something that is intrinsically neutral because it is generally a neutral molecule if you add plus one and negative with one you get 0. but you have a distribution of partial charges within this single molecule, so this is a polar covalent bond, so what I'm going to do now is summarize what we just considered, so we talk about ionic. bonds and we talk about covalent bonds now within a covalent bond you can have two types: it can be a polar covalent bond or you can have a non-polar covalent bond, so for the ionic bond we have the example of lithium fluoride now in an ionic bond. we have lithium ions it has a positive charge fluorine has a negative charge in a polar covalent bond we had molecules like carbon monoxide however we did not have a full charge but we had a partial charge carbon was partially positive and oxygen was partially negative so make sure you see the difference in ionic bonds, you have full charges like plus one or minus one, while in a polar covalent bond you can have partial charges, they could be 0.1.2, but it is not a full charge in a non-polar covalent bond like if. of the bromine molecule, the electrons in this molecule were shared equally, so there are no partial charges and if you remember, ionic bonds are usually formed by metals and non-metals, while covalent bonds usually consist of two non-metals. metals, whetherpolar covalent or non-polar covalent and Remember that the difference in for a polar covalent bond has to be 0.5 or more, for a non-polar covalent bond it is usually 0.4 or less, so that's basically it for this video, which is a summary sheet of what I have and there is one more thing I want. to mention ammonium nitrate, this is one of those exceptions you should pay attention to.

Would you consider it ionic or covalent? Now, when looking at the elements nitrogen, hydrogen, and oxygen, you'll probably notice that there are no metals in this example, so you might think this is a situation between two nonmetals, which is true. However, it is not. You can't rule out ionic bonds in this case because it turns out that this compound has a mix of ionic and covalent bonds. Ammonium is a polyatomic ion with a positive charge. and nitrate is a polyatomic ion with negative charges so between the ammonium ion and the nitrate ion you have an ionic bond even though there are no metals so this is one of those exceptions where you have an ionic bond between two non-metals, so when you see a metal and a non-metal, it is normally an ionic bond if you see two In non-metals it is usually a covalent bond, but it could be an exception, as seen in this case, for this substance in particular, ammonium nitrate, we have covalent bonds within the polyatomic ion, so within the ammonium ion, which looks like this, the bond between hydrogen and nitrogen is a covalent bond it is a polar covalent bond the difference ian is greater than 0 .5 the electronegativity value for nitrogen is 3.0 for hydrogen 2.1 and for the nitrate ion which looks like this we have another polar covalent bond between a nitrogen and an oxygen the difference is 0.5, so within of this molecule you have ionic bonds and covalent bonds, so there are exceptions that you should pay attention to, but the things that were mentioned in this video are general rules to keep in mind.