Understanding Ionic and Covalent Bonds

In this video, we're going to discuss the difference between ionic and covalent bonding. In ionic bonding, electrons are transferred from one element to another. typically ionic bonds contain ions. In a covalent bond electrons are shared. But let's go over ionic bonding first. Let's consider the reaction between an atom of sodium and an atom of chlorine. Sodium as an atom has one valence electron. If you look where it is in the periodic table, it's in the first column. It's in group 1a of the periodic table, and elements in that group all contain one valence electron. A valence electron is simply the electrons in the last, or outermost, energy level. Chlorine, which is a halogen, contains seven valence electrons. It's in group 7a of the periodic table. The halogens are very reactive nonmetals. And the alkali metals where sodium is found are very reactive metals. Metals like to give away electrons, and so they form positively charged ions. Non-metals, they like to receive electrons, and so they form negatively charged anions. So sodium is going to give chlorine one of its electrons, or valence electrons, since it only has one. So as sodium loses that one valence electron, it's going to acquire a positive charge and as chlorine gains that electron it acquires a negative charge. Now going back to physics if you have two like charges next to each other what's going to happen? Like charges repel. They're going to feel an electric force that repels them or pushes them away from each other. But what's going to happen if you have a positive and a negative charge next to each other? These two are attracted to each other. They feel a force of attraction that pulls them together. And so that's what's happening between the sodium ion and the chloride ion. The sodium ion, which now has a net positive charge, is attracted to the chloride ion, which has a negative charge. And so these two, they feel a force of attraction. That force of attraction that electrostatic force it binds them together and so that creates the ionic bond so keep this in mind within ionic bonds you have a transfer of electrons and The bonds that hold them or as a result of the electrostatic forces between Opposite charges keep in mind opposite charges attract each other So now let's move on into covalent bonding Let's look at hydrogen. A hydrogen atom has one valence electron and it's in the first row of the periodic table. Elements in the first row, they want to have a total of two electrons in their outer energy level. Second row elements, they want to have eight electrons. So elements like oxygen and fluorine, they want to satisfy their octet. They want to have eight electrons. But hydrogen and helium, They can only have two electrons in their first shell. So each of these hydrogens, they need one more electron to fill that first shell with a total of two electrons. And both of these elements are the same. So what they're going to do is they're going to share their electrons. And so these two, they're going to form a bond. So when you see a bond, this bond represents the sharing of two electrons. And so this is a covalent bond. Anytime you have sharing of electrons, it's a covalent bond. Now there's two types of covalent bonds you need to be familiar with. Polar covalent bonds and nonpolar covalent bonds. The bond between two hydrogen atoms is considered to be a nonpolar covalent bond. The reason why it's nonpolar is because the electrons are shared equally between those two hydrogen atoms. Now, if you look at the bond between hydrogen and fluorine, the elements are different. Fluorine is much more electronegative than hydrogen. Because fluorine is electronegative, it's going to pull the electrons toward itself. Now granted, the electrons are still being shared, but they're being shared unequally. And whenever you have an unequal sharing of electrons, you have a polar covalent bond, as opposed to a nonpolar covalent bond. So because fluorine is more electronegative, as it pulls the electrons toward itself, fluorine is going to acquire a partial negative charge, and hydrogen is going to be partially positive. And whenever you have an object... where one side is positive and the other side is negative, you have a dipole, you have a polarized object. And this is what it means to be polar. You have an unequal distribution of charge. One side is positive, one side is negative. So the electrons, they're not distributed evenly in that molecule. The electrons spend more time closer to fluorine because it's more electronegative. Electronegativity is the ability of an atom to attract an electron. electron toward itself and flooring it does a good job in doing that so now you know what a polar covalent bond is it's a bond where you have unequal sharing of electrons and a non polar covalent bond is a bond where you have equal sharing of electrons now let's go over some practice problems I want you to classify the following bonds as being ionic, polar covalent, or non-polar covalent. So let's start with the first one. MgO, magnesium oxide. Is it ionic, polycovalent, or non-polycovalent? The first thing I would look for is to see if it's ionic. An ionic compound consists of a metal and a nonmetal. That's how you can easily identify it. Magnesium is a metal. Metals exist on the left side of the periodic table. Nonmetals exist on the right side of the periodic table. the right side. The nonmetals are on the upper right side, the metals are on the lower left side. So magnesium is a metal, and oxygen, which is on the upper right side of the periodic table, that's a nonmetal. So this is going to be ionic. Magnesium forms a plus 2 charge as an ion. It has two valence electrons. So in this bond, it's going to give away two electrons to oxygen. Oxygen which is a chalcogen. Magnesium is an alkaline earth metal. But oxygen, it has six valence electrons and needs two more to get to eight. So once it acquires those two electrons, it's going to have a negative charge. As you can see, this compound is composed of ions. Now what about two chlorine atoms? Chlorine is a nonmetal. Whenever you have two nonmetals with the same type of element, it's always going to be be a non-polar covalent. The electrons are shared equally because we have the same type of atom. Now what about sodium fluoride? Sodium is on the left side of the periodic table so it's a metal and fluorine is a halogen on the right side so that's a nonmetal. So sodium fluoride contains ionic bondant. Now what about HBr? Is it polar covalent? non polar covalent now the elements are different so that could be an indication that it might be polar covalent but you need to run a test you need to calculate the difference in election negativity if the election negativity difference is equal to or greater than 0.5 most textbooks they use this number if it's 0.5 or more than the bond is considered to be polar covalent If it's less than 0.5, if it's 0.4 or less, then it's considered to be non-political valence. So if you need the election negativity values, you can go to Google Images and type in election negativity table and you'll see some tables come up. Now I've seen different tables with different values. They don't vary much, but sometimes they do vary. So if you're doing a homework problem, use whatever table your book gives you. In the table that I use, hydrogen has an electronegativity value of 2.1. Bromine, it's about 2.8. And so the EN difference is 0.7. Therefore, this is going to be polar covalent. I'm going to write PC for polar covalent. Now what about iodine? Monobromide what is the difference in electronegativity? iodine has an electronegativity value of 2.5 and for bromine 2.8 so the en difference is about about point three which means that it's relatively non polar covalent so I'm gonna write NC again make sure you use the table that your book provides because if the values are slightly different the result might be different but the idea is that you want to find an EN difference of 0.5 or more to see if it's polar or not so let's try some more examples Determine if the following bonds is polar covalent, non-polar covalent, or ionic. So let's look at carbon and hydrogen. Carbon has an electronegativity value of 2.5, and for hydrogen it's 2.1. so the EN difference is 0.4. For this one I would commit this memory anytime you see carbon hydrogen it's going to be nonpolar. This is a very common example that you'll see within chemistry and even organic chemistry. Now what about the OH bond? Whenever hydrogen is bonded to oxygen, nitrogen, or fluorine, you have a special case of bonding known as hydrogen bonds. Whenever you have hydrogen bonds, it's going to be polar, by the way. Oxygen has an electronegativity value of 3. point five so three point five minus two point one the difference is huge so one point four this bond is very polar so this is polar covalent this is non polar covalent now if the two atoms are the same and they're both not nonmetals it's going to be not political you don't really need to do the calculation floyd has an election a TV value 4.0 4 minus 4 is 0 which is less than 0.5 now calcium sulfide for this you really don't need the election a TV values you just need to know that calcium is a metal and sulfur is a nominal and then so you could say it's ionic if you have one element all the the way to the left side of the periodic table and another all the way to the right side, it's going to be ionic. So that is it for this video. Now you understand the difference between ionic and covalent bonding. So thanks for watching and have a great day.

But let's go over ionic bonding first. Let's consider the reaction between an atom of sodium and an atom of chlorine. Sodium as an atom has one valence electron.

If you look where it is in the periodic table, it's in the first column. It's in group 1a of the periodic table, and elements in that group all contain one valence electron. A valence electron is simply the electrons in the last, or outermost, energy level. Chlorine, which is a halogen, contains seven valence electrons.

It's in group 7a of the periodic table. The halogens are very reactive nonmetals. And the alkali metals where sodium is found are very reactive metals.

Metals like to give away electrons, and so they form positively charged ions. Non-metals, they like to receive electrons, and so they form negatively charged anions. So sodium is going to give chlorine one of its electrons, or valence electrons, since it only has one. So as sodium loses that one valence electron, it's going to acquire a positive charge and as chlorine gains that electron it acquires a negative charge. Now going back to physics if you have two like charges next to each other what's going to happen?

Like charges repel. They're going to feel an electric force that repels them or pushes them away from each other. But what's going to happen if you have a positive and a negative charge next to each other?

These two are attracted to each other. They feel a force of attraction that pulls them together. And so that's what's happening between the sodium ion and the chloride ion.

The sodium ion, which now has a net positive charge, is attracted to the chloride ion, which has a negative charge. And so these two, they feel a force of attraction. That force of attraction that electrostatic force it binds them together and so that creates the ionic bond so keep this in mind within ionic bonds you have a transfer of electrons and The bonds that hold them or as a result of the electrostatic forces between Opposite charges keep in mind opposite charges attract each other So now let's move on into covalent bonding Let's look at hydrogen.

A hydrogen atom has one valence electron and it's in the first row of the periodic table. Elements in the first row, they want to have a total of two electrons in their outer energy level. Second row elements, they want to have eight electrons.

So elements like oxygen and fluorine, they want to satisfy their octet. They want to have eight electrons. But hydrogen and helium, They can only have two electrons in their first shell.

So each of these hydrogens, they need one more electron to fill that first shell with a total of two electrons. And both of these elements are the same. So what they're going to do is they're going to share their electrons. And so these two, they're going to form a bond. So when you see a bond, this bond represents the sharing of two electrons.

And so this is a covalent bond. Anytime you have sharing of electrons, it's a covalent bond. Now there's two types of covalent bonds you need to be familiar with. Polar covalent bonds and nonpolar covalent bonds. The bond between two hydrogen atoms is considered to be a nonpolar covalent bond.

The reason why it's nonpolar is because the electrons are shared equally between those two hydrogen atoms. Now, if you look at the bond between hydrogen and fluorine, the elements are different. Fluorine is much more electronegative than hydrogen.

Because fluorine is electronegative, it's going to pull the electrons toward itself. Now granted, the electrons are still being shared, but they're being shared unequally. And whenever you have an unequal sharing of electrons, you have a polar covalent bond, as opposed to a nonpolar covalent bond.

So because fluorine is more electronegative, as it pulls the electrons toward itself, fluorine is going to acquire a partial negative charge, and hydrogen is going to be partially positive. And whenever you have an object... where one side is positive and the other side is negative, you have a dipole, you have a polarized object. And this is what it means to be polar.

You have an unequal distribution of charge. One side is positive, one side is negative. So the electrons, they're not distributed evenly in that molecule. The electrons spend more time closer to fluorine because it's more electronegative.

Electronegativity is the ability of an atom to attract an electron. electron toward itself and flooring it does a good job in doing that so now you know what a polar covalent bond is it's a bond where you have unequal sharing of electrons and a non polar covalent bond is a bond where you have equal sharing of electrons now let's go over some practice problems I want you to classify the following bonds as being ionic, polar covalent, or non-polar covalent. So let's start with the first one.

MgO, magnesium oxide. Is it ionic, polycovalent, or non-polycovalent? The first thing I would look for is to see if it's ionic. An ionic compound consists of a metal and a nonmetal.

That's how you can easily identify it. Magnesium is a metal. Metals exist on the left side of the periodic table.

Nonmetals exist on the right side of the periodic table. the right side. The nonmetals are on the upper right side, the metals are on the lower left side.

So magnesium is a metal, and oxygen, which is on the upper right side of the periodic table, that's a nonmetal. So this is going to be ionic. Magnesium forms a plus 2 charge as an ion. It has two valence electrons.

So in this bond, it's going to give away two electrons to oxygen. Oxygen which is a chalcogen. Magnesium is an alkaline earth metal. But oxygen, it has six valence electrons and needs two more to get to eight.

So once it acquires those two electrons, it's going to have a negative charge. As you can see, this compound is composed of ions. Now what about two chlorine atoms?

Chlorine is a nonmetal. Whenever you have two nonmetals with the same type of element, it's always going to be be a non-polar covalent. The electrons are shared equally because we have the same type of atom.

Now what about sodium fluoride? Sodium is on the left side of the periodic table so it's a metal and fluorine is a halogen on the right side so that's a nonmetal. So sodium fluoride contains ionic bondant.

Now what about HBr? Is it polar covalent? non polar covalent now the elements are different so that could be an indication that it might be polar covalent but you need to run a test you need to calculate the difference in election negativity if the election negativity difference is equal to or greater than 0.5 most textbooks they use this number if it's 0.5 or more than the bond is considered to be polar covalent If it's less than 0.5, if it's 0.4 or less, then it's considered to be non-political valence.

So if you need the election negativity values, you can go to Google Images and type in election negativity table and you'll see some tables come up. Now I've seen different tables with different values. They don't vary much, but sometimes they do vary. So if you're doing a homework problem, use whatever table your book gives you. In the table that I use, hydrogen has an electronegativity value of 2.1.

Bromine, it's about 2.8. And so the EN difference is 0.7. Therefore, this is going to be polar covalent.

I'm going to write PC for polar covalent. Now what about iodine? Monobromide what is the difference in electronegativity?

iodine has an electronegativity value of 2.5 and for bromine 2.8 so the en difference is about about point three which means that it's relatively non polar covalent so I'm gonna write NC again make sure you use the table that your book provides because if the values are slightly different the result might be different but the idea is that you want to find an EN difference of 0.5 or more to see if it's polar or not so let's try some more examples Determine if the following bonds is polar covalent, non-polar covalent, or ionic. So let's look at carbon and hydrogen. Carbon has an electronegativity value of 2.5, and for hydrogen it's 2.1. so the EN difference is 0.4. For this one I would commit this memory anytime you see carbon hydrogen it's going to be nonpolar.

This is a very common example that you'll see within chemistry and even organic chemistry. Now what about the OH bond? Whenever hydrogen is bonded to oxygen, nitrogen, or fluorine, you have a special case of bonding known as hydrogen bonds. Whenever you have hydrogen bonds, it's going to be polar, by the way. Oxygen has an electronegativity value of 3. point five so three point five minus two point one the difference is huge so one point four this bond is very polar so this is polar covalent this is non polar covalent now if the two atoms are the same and they're both not nonmetals it's going to be not political you don't really need to do the calculation floyd has an election a TV value 4.0 4 minus 4 is 0 which is less than 0.5 now calcium sulfide for this you really don't need the election a TV values you just need to know that calcium is a metal and sulfur is a nominal and then so you could say it's ionic if you have one element all the the way to the left side of the periodic table and another all the way to the right side, it's going to be ionic.

So that is it for this video. Now you understand the difference between ionic and covalent bonding. So thanks for watching and have a great day.

Transcript for:Understanding Ionic and Covalent Bonds

Transcript for:
Understanding Ionic and Covalent Bonds