Understanding Chemical Bonding in Organic Compounds

In this video we're going to talk about chemical bonding of organic compounds. So let's get started. You probably have heard about organic compounds and inorganic compounds in your general chemistry class. Organic compounds are usually composed of the elements carbons and hydrogens and inorganic compounds are composed of most of the time metals and non-metal elements. Organic compounds are easily decomposed into simpler substance by heating. The reaction that you have learned in your general chemistry class is called combustion reactions. It produces the product carbon dioxide and water. But inorganic substances, they cannot be decomposed into simpler substance by heating. Inorganic compounds one can synthesize quite easily in the lab, but synthesis of organic compounds is really, really hard. So these are the two primary main differences between organic compounds and inorganic compounds. So what is so special about organic compounds? Again, organic compounds are usually tend to be molecular. So they do not, they are not ionic. They are molecular, they're neutral. They're mostly composed of just six elements, carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus. You can see all are non-metals. So carbon is a non-metal, hydrogen, oxygen, nitrogen, sulfur, and phosphorus are non-metals. Mostly, most of the organic compounds are composed of carbon and hydrogen. There are certain cases where oxygen, nitrogen, sulfur, phosphorus can also be present in organic compound structure. Organic compounds can be found in solid form, can be found in liquid form, as well as in gaseous form. The solubility of organic compounds in water varies depending on which of the other elements are attached to the carbon atoms and how many they are. If it is a small molecule and it has some heteroatom, for example, methanol, CH3OH, they are miscible with water. They are soluble in water. But if it is a longer chain alcohol, which has more carbon atoms attached to it, like in this case, we have 10 carbon atoms. then those type of molecules are usually insoluble in water. What is so special about the carbon? So since we talk about organic compound is the carbon-based compound, so we first need to know what is the special type of characteristics can be found on carbon, but cannot be found in any other atoms, other elements. So again, the carbon atoms can do some unique... things that you cannot find the other atoms can do the same type of job carbon can bond to as many as four other atoms but very there are very few few elements they can form for they can bond to other four atoms bonds to carbons are usually very strong and non-reactive so as you see here in this structure these are organic molecular structures so carbon they can attached with four three different hydrogens and one carbon so each carbon is bonded with four atoms the simpler example is the methane here's the carbon one is the central carbon and so this is a test with four hydrogen atoms and if it is a straight chain molecule like this there means a bonds between carbon and carbon that bond is really really strong bonds and they are not reactive at room temperature Carbon atoms can attest together in a long chain. That means the carbon they can attest to another carbon, to another carbon, to another carbon. They get from long chain or even they can attest together to form a ring like structure like this. So here we have six carbon atoms. They attest together from six member ring. We call cyclohexane. And also the carbon atoms can form a single bond. You can see carbon-carbon bond. Because here is... Connected by a single line single bond here the carbon and hydrogen is connected by a single line equal single bonds It can be a double bond so carbon can form a double bonds with another carbon atoms or it can Like a tester another carbon atoms by triple bonds. So as you see here, there are many properties The carbon elements can exhibit but you cannot find similar properties in other elements As I was showing you that carbon-carbon bonds are really strong and non-reactive. If you want to compare with other atoms you will find you'll find interesting so carbon carbon single bond here the bond energy is 347 kilojoule and this for example is simple molecules ethane the carbon carbon bonds here is a non-reactive in the air but whereas if you are comparing with sulfur sulfur bonds alpha sulfur bonds is relatively lower 214 kilo 214 kilojoule and they are extremely reactive silicon bond, silicon-silicon bond, they spontaneously combust in air. Nitrogen-nitrogen bond, they're extremely reactive, they're kind of explosive in nature. Peroxides, very, very reactive, they're also explosive in nature. So it means you cannot have any type of carbon-based organic compound based on sulfur-sulfur or silicon-silicon, nitrogen-nitrogen or oxygen-oxygen, purely oxygen-oxygen bond. As you see, they are very, very reactive. They are not stable. They will not form a stable compound. Whereas the carbon, they're non-reactive in air. They form stable organic compounds. This is the specialty of carbon atoms. When you talk about the carbon bonding, we know the carbon forms four bonds every time. That's how you can see here. You have one, two, three, four, four bonds. Each bond has two electrons, so carbon can have eight. share electrons on its valence shell so that's how they attend the octet role octet electrons on their valence shells by sharing electrons with other four atoms when carbon has four single bonds when carbon has four single bond the shape is d-dehedral when carbon has one triple bond one single bond or two double bond, the shape is usually linear shape. When carbon has two single bonds and one double bond, the shape is trigonal planar. If you look at this structure here, you can see the carbon in the central atom is bonded with four hydrogen. The shape is tetrahedral. If the carbon is bonded with another atom by a triple bond, the shape is usually linear shape. And when the carbon bonded with... another atom by double bonds and two single bonds. So usually they're two-unit planar. That's the shape of the carbon molecule. Now we're going to learn a little bit more details about the bonding, chemical bonds, chemical bonding story. So in your general chemistry, in our general chemistry class, you have learned the chemical bonds, usually that holds atoms or ions together in the compounds. For example here, if you have atom 1 and atom 2, if they want to stick together by bonds, by chemical bonds, they can do it in two ways. Either they can share their valence electrons and stick together like this way, A to electrons A, that means they're sharing electrons. Or they can stick together by ionic bonds. The one will form cation, another will form anions. So that way they can stick together. So it means you can have two possibilities. There are two types of bonding. One is the ionic bonds. In that case, one atom will completely transfer its electrons. One electron or more than one electron to another atom. And form oppositely charged ions that attract one another. Usually you can find that type of ionic bonds in ionic compounds. So ionic compounds atoms are kind of hold atoms are held together by our new bonds in covalent bonding case the atoms they are basically they are held together by um by sharing their valence electrons so they can share their valence electrons uh so that sharing of valence from balance electrons with covalent bonds it means in molecules they in molecules the atoms are held together by covalent bonds like this second category that we're talking about. Now let's take a look more detailed picture of the ionic bonds and covalent bonds. When you talk about the ionic bonds usually we're meaning the electrons are transferred between metal atoms to non-metal atoms. On the other hand, ionic compounds are formed by metals and non-metal atoms. Usually what happens, the metal loses electrons from the valence shell. They form positively charged ions, we call in chemistry called cations. When non-metal ions gain that electrons and add into their valence shell, they turn into negatively charged ions in organic chemistry we call anions. So atom 1 and atom 2, if you look at in this case, atom 1 is losing electrons to atom 2, turning into cations. and an atom two after accepting the electron turning into an anion. So these cations and anions are held together by ionic bonds by columbic inter-columbic electrostatic attraction or clubbing, columbic interactions. So this is why we call the ionic bonds. And the reason why the atom one is transferring electron to atom two, If you recall from your general chemistry class, you probably will remember because of the novel gas configurations. So atom 1 will try to gain a novel gas configuration by losing electrons. Atom 2 will try to gain the electrons, will accept the electron because it wants to attain the novel gas electron configuration. So what is novel gas electron configurations? Usually elements, they tend to gain or lose electrons. So they will have the same number of electrons as a noble gas. The number of electrons could be eight except for helium which has two to become more stable. For example if you look at in this case sodium atoms, a metallic sodium, it has 11 electrons, total of 11 electrons. So one valence electrons. So it will lose that one valence electrons to form sodium ions. And now in the sodium ions you can see it has eight valence electrons. So two, four, six and eight. which is similar like neon electron, neon electron configuration. Neon has eight electrons on its valence shell. So metallic sodium therefore wants to lose that electron, the one single valence electrons from its outer shell, and will form sodium ion, sodium cation, so that it can attend the same electron configuration as neon. So the tendency of an atom in a molecule is to have eight electrons in the outer shells. is called octet rule. If it is hydrogen, then they would like to have two electrons in the outer shells, we call Dewitt rule. Now we're talking about the covalent bonding. Covalent bond means sharing of a pair of electrons between two non-metal atoms. So this is the thing that you need to remember. When you talk about the covalent bonds, we're talking about the sharing of electrons between two non-metal atoms. So if you have atom 1 and atom 2, Those two are non-metal atoms, none of them are metals. So those two are non-metals. So what they are going to do, atom 1 and atom 2, they will share their electrons, so that way they can attain the electronic, novel gas electronic configuration. So this, the bonds between, bonds after sharing these electrons are generatrix covalent bonds, often found in molecules. So in molecules, atoms are held together by covalent bonds. molecules like hydrochloric acid, water, and H3N, methane molecules. You can see hydrochloric acid is two non-metal atoms, hydrogen and chlorine, and in water, oxygen, hydrogen bonds are covalent bonds. In ammonia, nitrogen and hydrogen bonds are kind of covalent bonds. In methane, carbon, hydrogen bonds are covalent bonds. If you look at the structure for hydrochloric acid, You can see the hydrogen has one balanced electron, chlorine has one balanced electron. So they can share their electrons. Hydrogen can have these two electrons on it. So that can have those two electrons so it can add and do an electron configuration. Chlorine on the other hand after sharing the electrons it can have eight valence electrons around it. Two, four, six, eight. So it can add in the electron in the octet form. So that's the driving force that they're kind of forming the covalent bond. So again, when we talk about the ionic bonds, ionic bonds are basically bonds between metal and nonmetal atoms. And covalent bonds are bonds between two nonmetal atoms. Covalent bonds can also be shown as a line to represent the pair of electrons. For example, in hydrogen, two hydrogen atoms, they're non-metal elements. Therefore, the bonds between them are covalent bonds. So, it can be shown by single lines. If it is a double bond, if it is a single line, it's a single bond. If it is a molecule like carbon dioxide here, you can see the carbon is actually bonded with oxygens by two single lines, we call double bond. In nitrogen, so two nitrogen atoms are bonded together by three lines, we call triple bond. Single bonds are sharing of one pair of electrons. You can see here you have one pair of electrons, two electrons by two atoms and double bonds sharing two pairs of electrons, so a total of four electrons shared by two atoms and it can be found in carbon dioxide or in oxygen in this example. Triple bond means sharing of three pairs of electrons means a total of six electrons are shared by two atoms. And one thing also you have to remember, single bonds are usually the longest bonds and weakest bond. Double bonds are shorter and stronger than single bonds and triple bonds are the shortest bond and strongest bond. It is strongest strongest bonds, stronger than single and double bonds. Now we are going to talk about the topic called electronegativity and polarity. You have learned the definitions in your general chemistry class already. Electronegativity of an atom means the ability of an atom in a bond to attract shared electrons to itself. Larger electronegativity means atom attracts more strongly the shared electrons toward yourself. If you look at on the periodic table, it usually increases across the period from left to right on periodic table, and it decreases down the group top to bottom on periodic table. If you look at the electronegative values for hydrogen atoms here, it is 2.1, it's after boron and before carbon, somewhere between boron and carbon, the electronegative hydrogens. is locating here. So if you know this electronegativity chart here, electronegativity chart for each element, one can actually quantitatively predict whether the bonds between two atoms are polar, nonpolar, or ionic type of bonds. So there is a rule, if you look at the electronegativity difference values between two atoms, if it is less than 0.5, we call nonpolar covalent bonds. and if it is somewhere between 0.5 to 1.9 we call polar covalent bonds, if it is greater than 1.9 we call ions, ions formed. So let's see some example here. Now let's say you are given this periodic tables, you know the electronegative values for each atom, and from there you want to predict whether the bonds are here are polar, non-polar, or ionic. So the first one here is the fluorine and hydrogen. If you look at the fluorine is 4.0 and hydrogen is 2.1. So then 4.0 minus 2.1 is 1.9. So which is larger than 0.5. So it is falling in the range 0.5 to 1.9. So the fluorine hydrogen bond should be polar bonds. Oxygen, hydrogen, again oxygen is 3.5 and hydrogen is 2.1. So 3.5 and 3.5 and 2.1 give you 1.4. So this is between 0.5 to 1.9. So each bond is polar bond. Nitrogen hydrogen bond is again 0.9. So nitrogen is 3.0 minus 2.1, so 0.9. Whereas the carbon hydrogen bonds, carbon has 2.5 and hydrogen has 2.1, so it's 0.4. It's less than 0.5. Therefore carbon hydrogen bonds are non-polar bonds. So if you want to compare the sodium chloride, sodium chloride, so Cl, chlorine and sodium bonds, if you want to look at, so chlorine is 3.0 and sodium is 0.9, so that's a 2.1, so it's greater than 1.9, that means it's an ionic bond. So one can also predict whether it's a polar bond, nonpolar bond or ionic bond based on just looking at the electronegativity. values qualitatively. For example, if you want to see a bond between A and B and if you look at that bond closely, and if you find that A and B have, those both atoms have equal electronegativity values, then they can share their bond electrons equally, and those type of bonds become non-polar covalent bonds. Again, it's kind of understandable, if you look at A and B, if they have the same electronegativity, that means the electronegativity difference would be 0, which is less than 0.5, So, therefore, one can say it's a non-polar covalent bond if you use that mathematical relations. The most common example for non-polar covalent bonds in diatomic molecules, so when you have a diatomic molecule like hydrogens, oxygen, nitrogen, chlorine, fluorine, iodine, bromine, so in those molecules, like the two atoms are forming a... covalent bonds like in bromine gas. In bromine, if you look at bromine and bromine bonds, so two electronegativity, two same atoms forming that bond, so that means the bond would be a nonpolar covalent bond. Another type of covalent bonds is called polar covalent bonds. When you have A and B forming a covalent bond and they have different electronegativity values, then the polar covalent bond will result. We say polar because it has two poles. So one side it has a positive end, another side it has a negative end. If you look at this polar cobalt bonds between hydrogen and fluorine, you can see hydrogen has a delta positive charge and fluorine has a delta negative charge. Because the electrons spend, the shared electrons spend more time around fluorine and they spend less time around hydrogen. If fluorine gets a partial negative charge because electrons spending more time on it So we usually indicated by Delta negative charge and hydrogen get a partial positive charge We indicated by Delta negative charge So this is why because of this two pole we call polar bonds and this is a cobalt bonds You can polar cobalt bonds. So Again, the Delta notation that we use here. We kind of rely on which one is the more electronegative atom. So electrons are usually concentrated around the more electronegative atoms in the molecules and that electronegative atoms can say partial negative charge indicated by Delta minus and since electrons spend less time around the other atoms, so other atoms gain a partial positive charge that indicated by Delta positive. Another example here is the cobalt bond between iodine and chlorine. Chlorine is more electronegative atom. So you have a delta negative charge on chlorine and delta positive charge on iodine. If you have a covalent bond between carbon and fluorine, so fluorine is more electronegative than carbon, so carbon will get delta positive charge and fluorine will get delta negative charge. So that takes us to our next lecture problem here. It says use the delta notations to indicate which atom in each bond is more electronegative and then use an arrow to point towards the negative pole. If you look at this example here, carbon, chlorine, nitrogen, chlorine, and hydrogen, boron, oxygen, hydrogens. So if you want, you can pause the video and try to answer these questions on your own, and then you can check your answer with the answer I'm going to show you in a second. If you have carbon-chlorine bonds, so carbon and chlorine, chlorine is more electronegative than carbon, so chlorine will get delta negative charge and carbon will get delta positive charge. Nitrogen fluorine case fluorine is more negative electronegative than nitrogen. So fluorine will get delta negative charge and nitrogen will get delta positive charge for hydrogen boron. We have learned previously in the electronegative value chart that boron has electronegative values 2.0 and hydrogen is 2.1. So hydrogen is more electronegative than boron. So the hydrogen will have a delta negative charge and boron will have delta positive charge. OH case, so oxygen has a delta negative charge and hydrogen is delta positive charge because oxygen is more electronegative than hydrogen. So if you want to draw the dipole arrow, it will look like this. It will start from carbon to chlorine. For this case, it will start from nitrogen to chlorine. For this case, it will start from boron to hydrogen. And for OH case, it starts from hydrogen to oxygen. Now take us to our next lecture problem here, which of the following bonds has a dipole and for those that have dipoles on which atom to the first positive and first negative charge. If you look at these bonds here, carbon oxygen is two electronegative atoms. This is a polar covalent bonds. For hydrogen and hydrogen, you have two same similar atoms. So this is a non polar covalent bonds. On hydrogen and fluorine case, this is also polar covalent bonds because two negative electro negative elements here two different elect two different atoms having different electronegative values for hydrocarbon and hydrogens carbon and hydrogen carbon has electronegative values 2.5 hydrogen has electronegative values is 2.1 carbon hydrogens bonds we know is the electronegativity difference is 0.4 therefore carbon hydrogens that bond is non-polar covalent bonds this is The thing that you must need to remember is not every time when you have a covalent bond having two different atoms and that bond would be a polar bond. It's not true. For carbon-hydrogen case, it is a non-polar covalent bond. Only you can see the carbon and oxygen. That's a kind of polar bonds. And for hydrogen and fluorine, this is also polar bonds. Again, the diatomic... and diatomic molecules and also the carbon hydrogen bonds are nonpolar covalent bonds. That take us to our next lecture problem here identify bonds in the following by circling one for each. So we have here the bonds in hydrofluoric acid. Will that be ionic, polar or nonpolar covalent bonds? If you want you can pause this video and then you can find the answer. or check your answer. The answer I'm going to show you in a second. So the bonds in hydroponic acid, so hydrogen and fluorine, this is two different elements and they have different electron negative values. So it would be in polar covalent bonds. If you want to look at the bonds in fluorine, it's a diatomic molecule, same atom, so it's a non-polar covalent bond. The bonds in K2O, So you have metals and nonmetals combination that should be ionic. You have bonds in CO. You have carbon and oxygen, two different electronegative atoms. It is not carbon-hydrogen bonds. Again, remember, carbon-hydrogen bonds is non-polar covalent bonds. That's the exceptional thing that you must need to remember. But all other like carbon-oxygen, hydrogen-fluorine, nitrogen-carbon, so those are different elements, different electronegative values. those bonds would be polar covalent bonds. The bonds in O2, again, that's a non-polar covalent bonds. The bonds in magnesium chloride, again, metal non-metal combinations and ionic bonds. And the bonds in NO, so nitrogen and oxygen, two different elements, different electronegative values, it would be polar covalent bonds. So that's how you have to identify whether the bond is polar bonds or is a non-polar covalent bonds or is an ionic bond. So that's all for this video. We'll talk about the organic chemical structure, how to draw the chemical structure for organic compounds in our next video.

The reaction that you have learned in your general chemistry class is called combustion reactions. It produces the product carbon dioxide and water. But inorganic substances, they cannot be decomposed into simpler substance by heating.

Inorganic compounds one can synthesize quite easily in the lab, but synthesis of organic compounds is really, really hard. So these are the two primary main differences between organic compounds and inorganic compounds. So what is so special about organic compounds? Again, organic compounds are usually tend to be molecular.

So they do not, they are not ionic. They are molecular, they're neutral. They're mostly composed of just six elements, carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus.

You can see all are non-metals. So carbon is a non-metal, hydrogen, oxygen, nitrogen, sulfur, and phosphorus are non-metals. Mostly, most of the organic compounds are composed of carbon and hydrogen. There are certain cases where oxygen, nitrogen, sulfur, phosphorus can also be present in organic compound structure. Organic compounds can be found in solid form, can be found in liquid form, as well as in gaseous form.

The solubility of organic compounds in water varies depending on which of the other elements are attached to the carbon atoms and how many they are. If it is a small molecule and it has some heteroatom, for example, methanol, CH3OH, they are miscible with water. They are soluble in water. But if it is a longer chain alcohol, which has more carbon atoms attached to it, like in this case, we have 10 carbon atoms.

then those type of molecules are usually insoluble in water. What is so special about the carbon? So since we talk about organic compound is the carbon-based compound, so we first need to know what is the special type of characteristics can be found on carbon, but cannot be found in any other atoms, other elements. So again, the carbon atoms can do some unique...

things that you cannot find the other atoms can do the same type of job carbon can bond to as many as four other atoms but very there are very few few elements they can form for they can bond to other four atoms bonds to carbons are usually very strong and non-reactive so as you see here in this structure these are organic molecular structures so carbon they can attached with four three different hydrogens and one carbon so each carbon is bonded with four atoms the simpler example is the methane here's the carbon one is the central carbon and so this is a test with four hydrogen atoms and if it is a straight chain molecule like this there means a bonds between carbon and carbon that bond is really really strong bonds and they are not reactive at room temperature Carbon atoms can attest together in a long chain. That means the carbon they can attest to another carbon, to another carbon, to another carbon. They get from long chain or even they can attest together to form a ring like structure like this.

So here we have six carbon atoms. They attest together from six member ring. We call cyclohexane. And also the carbon atoms can form a single bond. You can see carbon-carbon bond.

Because here is... Connected by a single line single bond here the carbon and hydrogen is connected by a single line equal single bonds It can be a double bond so carbon can form a double bonds with another carbon atoms or it can Like a tester another carbon atoms by triple bonds. So as you see here, there are many properties The carbon elements can exhibit but you cannot find similar properties in other elements As I was showing you that carbon-carbon bonds are really strong and non-reactive. If you want to compare with other atoms you will find you'll find interesting so carbon carbon single bond here the bond energy is 347 kilojoule and this for example is simple molecules ethane the carbon carbon bonds here is a non-reactive in the air but whereas if you are comparing with sulfur sulfur bonds alpha sulfur bonds is relatively lower 214 kilo 214 kilojoule and they are extremely reactive silicon bond, silicon-silicon bond, they spontaneously combust in air. Nitrogen-nitrogen bond, they're extremely reactive, they're kind of explosive in nature.

Peroxides, very, very reactive, they're also explosive in nature. So it means you cannot have any type of carbon-based organic compound based on sulfur-sulfur or silicon-silicon, nitrogen-nitrogen or oxygen-oxygen, purely oxygen-oxygen bond. As you see, they are very, very reactive.

They are not stable. They will not form a stable compound. Whereas the carbon, they're non-reactive in air. They form stable organic compounds. This is the specialty of carbon atoms.

When you talk about the carbon bonding, we know the carbon forms four bonds every time. That's how you can see here. You have one, two, three, four, four bonds. Each bond has two electrons, so carbon can have eight.

share electrons on its valence shell so that's how they attend the octet role octet electrons on their valence shells by sharing electrons with other four atoms when carbon has four single bonds when carbon has four single bond the shape is d-dehedral when carbon has one triple bond one single bond or two double bond, the shape is usually linear shape. When carbon has two single bonds and one double bond, the shape is trigonal planar. If you look at this structure here, you can see the carbon in the central atom is bonded with four hydrogen. The shape is tetrahedral. If the carbon is bonded with another atom by a triple bond, the shape is usually linear shape.

And when the carbon bonded with... another atom by double bonds and two single bonds. So usually they're two-unit planar.

That's the shape of the carbon molecule. Now we're going to learn a little bit more details about the bonding, chemical bonds, chemical bonding story. So in your general chemistry, in our general chemistry class, you have learned the chemical bonds, usually that holds atoms or ions together in the compounds. For example here, if you have atom 1 and atom 2, if they want to stick together by bonds, by chemical bonds, they can do it in two ways. Either they can share their valence electrons and stick together like this way, A to electrons A, that means they're sharing electrons.

Or they can stick together by ionic bonds. The one will form cation, another will form anions. So that way they can stick together.

So it means you can have two possibilities. There are two types of bonding. One is the ionic bonds.

In that case, one atom will completely transfer its electrons. One electron or more than one electron to another atom. And form oppositely charged ions that attract one another.

Usually you can find that type of ionic bonds in ionic compounds. So ionic compounds atoms are kind of hold atoms are held together by our new bonds in covalent bonding case the atoms they are basically they are held together by um by sharing their valence electrons so they can share their valence electrons uh so that sharing of valence from balance electrons with covalent bonds it means in molecules they in molecules the atoms are held together by covalent bonds like this second category that we're talking about. Now let's take a look more detailed picture of the ionic bonds and covalent bonds.

When you talk about the ionic bonds usually we're meaning the electrons are transferred between metal atoms to non-metal atoms. On the other hand, ionic compounds are formed by metals and non-metal atoms. Usually what happens, the metal loses electrons from the valence shell.

They form positively charged ions, we call in chemistry called cations. When non-metal ions gain that electrons and add into their valence shell, they turn into negatively charged ions in organic chemistry we call anions. So atom 1 and atom 2, if you look at in this case, atom 1 is losing electrons to atom 2, turning into cations.

and an atom two after accepting the electron turning into an anion. So these cations and anions are held together by ionic bonds by columbic inter-columbic electrostatic attraction or clubbing, columbic interactions. So this is why we call the ionic bonds. And the reason why the atom one is transferring electron to atom two, If you recall from your general chemistry class, you probably will remember because of the novel gas configurations.

So atom 1 will try to gain a novel gas configuration by losing electrons. Atom 2 will try to gain the electrons, will accept the electron because it wants to attain the novel gas electron configuration. So what is novel gas electron configurations?

Usually elements, they tend to gain or lose electrons. So they will have the same number of electrons as a noble gas. The number of electrons could be eight except for helium which has two to become more stable. For example if you look at in this case sodium atoms, a metallic sodium, it has 11 electrons, total of 11 electrons.

So one valence electrons. So it will lose that one valence electrons to form sodium ions. And now in the sodium ions you can see it has eight valence electrons.

So two, four, six and eight. which is similar like neon electron, neon electron configuration. Neon has eight electrons on its valence shell. So metallic sodium therefore wants to lose that electron, the one single valence electrons from its outer shell, and will form sodium ion, sodium cation, so that it can attend the same electron configuration as neon.

So the tendency of an atom in a molecule is to have eight electrons in the outer shells. is called octet rule. If it is hydrogen, then they would like to have two electrons in the outer shells, we call Dewitt rule. Now we're talking about the covalent bonding. Covalent bond means sharing of a pair of electrons between two non-metal atoms.

So this is the thing that you need to remember. When you talk about the covalent bonds, we're talking about the sharing of electrons between two non-metal atoms. So if you have atom 1 and atom 2, Those two are non-metal atoms, none of them are metals. So those two are non-metals.

So what they are going to do, atom 1 and atom 2, they will share their electrons, so that way they can attain the electronic, novel gas electronic configuration. So this, the bonds between, bonds after sharing these electrons are generatrix covalent bonds, often found in molecules. So in molecules, atoms are held together by covalent bonds. molecules like hydrochloric acid, water, and H3N, methane molecules.

You can see hydrochloric acid is two non-metal atoms, hydrogen and chlorine, and in water, oxygen, hydrogen bonds are covalent bonds. In ammonia, nitrogen and hydrogen bonds are kind of covalent bonds. In methane, carbon, hydrogen bonds are covalent bonds. If you look at the structure for hydrochloric acid, You can see the hydrogen has one balanced electron, chlorine has one balanced electron. So they can share their electrons.

Hydrogen can have these two electrons on it. So that can have those two electrons so it can add and do an electron configuration. Chlorine on the other hand after sharing the electrons it can have eight valence electrons around it.

Two, four, six, eight. So it can add in the electron in the octet form. So that's the driving force that they're kind of forming the covalent bond. So again, when we talk about the ionic bonds, ionic bonds are basically bonds between metal and nonmetal atoms. And covalent bonds are bonds between two nonmetal atoms.

Covalent bonds can also be shown as a line to represent the pair of electrons. For example, in hydrogen, two hydrogen atoms, they're non-metal elements. Therefore, the bonds between them are covalent bonds.

So, it can be shown by single lines. If it is a double bond, if it is a single line, it's a single bond. If it is a molecule like carbon dioxide here, you can see the carbon is actually bonded with oxygens by two single lines, we call double bond.

In nitrogen, so two nitrogen atoms are bonded together by three lines, we call triple bond. Single bonds are sharing of one pair of electrons. You can see here you have one pair of electrons, two electrons by two atoms and double bonds sharing two pairs of electrons, so a total of four electrons shared by two atoms and it can be found in carbon dioxide or in oxygen in this example. Triple bond means sharing of three pairs of electrons means a total of six electrons are shared by two atoms.

And one thing also you have to remember, single bonds are usually the longest bonds and weakest bond. Double bonds are shorter and stronger than single bonds and triple bonds are the shortest bond and strongest bond. It is strongest strongest bonds, stronger than single and double bonds. Now we are going to talk about the topic called electronegativity and polarity.

You have learned the definitions in your general chemistry class already. Electronegativity of an atom means the ability of an atom in a bond to attract shared electrons to itself. Larger electronegativity means atom attracts more strongly the shared electrons toward yourself. If you look at on the periodic table, it usually increases across the period from left to right on periodic table, and it decreases down the group top to bottom on periodic table. If you look at the electronegative values for hydrogen atoms here, it is 2.1, it's after boron and before carbon, somewhere between boron and carbon, the electronegative hydrogens.

is locating here. So if you know this electronegativity chart here, electronegativity chart for each element, one can actually quantitatively predict whether the bonds between two atoms are polar, nonpolar, or ionic type of bonds. So there is a rule, if you look at the electronegativity difference values between two atoms, if it is less than 0.5, we call nonpolar covalent bonds. and if it is somewhere between 0.5 to 1.9 we call polar covalent bonds, if it is greater than 1.9 we call ions, ions formed.

So let's see some example here. Now let's say you are given this periodic tables, you know the electronegative values for each atom, and from there you want to predict whether the bonds are here are polar, non-polar, or ionic. So the first one here is the fluorine and hydrogen.

If you look at the fluorine is 4.0 and hydrogen is 2.1. So then 4.0 minus 2.1 is 1.9. So which is larger than 0.5. So it is falling in the range 0.5 to 1.9. So the fluorine hydrogen bond should be polar bonds.

Oxygen, hydrogen, again oxygen is 3.5 and hydrogen is 2.1. So 3.5 and 3.5 and 2.1 give you 1.4. So this is between 0.5 to 1.9.

So each bond is polar bond. Nitrogen hydrogen bond is again 0.9. So nitrogen is 3.0 minus 2.1, so 0.9.

Whereas the carbon hydrogen bonds, carbon has 2.5 and hydrogen has 2.1, so it's 0.4. It's less than 0.5. Therefore carbon hydrogen bonds are non-polar bonds. So if you want to compare the sodium chloride, sodium chloride, so Cl, chlorine and sodium bonds, if you want to look at, so chlorine is 3.0 and sodium is 0.9, so that's a 2.1, so it's greater than 1.9, that means it's an ionic bond. So one can also predict whether it's a polar bond, nonpolar bond or ionic bond based on just looking at the electronegativity.

values qualitatively. For example, if you want to see a bond between A and B and if you look at that bond closely, and if you find that A and B have, those both atoms have equal electronegativity values, then they can share their bond electrons equally, and those type of bonds become non-polar covalent bonds. Again, it's kind of understandable, if you look at A and B, if they have the same electronegativity, that means the electronegativity difference would be 0, which is less than 0.5, So, therefore, one can say it's a non-polar covalent bond if you use that mathematical relations. The most common example for non-polar covalent bonds in diatomic molecules, so when you have a diatomic molecule like hydrogens, oxygen, nitrogen, chlorine, fluorine, iodine, bromine, so in those molecules, like the two atoms are forming a... covalent bonds like in bromine gas.

In bromine, if you look at bromine and bromine bonds, so two electronegativity, two same atoms forming that bond, so that means the bond would be a nonpolar covalent bond. Another type of covalent bonds is called polar covalent bonds. When you have A and B forming a covalent bond and they have different electronegativity values, then the polar covalent bond will result.

We say polar because it has two poles. So one side it has a positive end, another side it has a negative end. If you look at this polar cobalt bonds between hydrogen and fluorine, you can see hydrogen has a delta positive charge and fluorine has a delta negative charge.

Because the electrons spend, the shared electrons spend more time around fluorine and they spend less time around hydrogen. If fluorine gets a partial negative charge because electrons spending more time on it So we usually indicated by Delta negative charge and hydrogen get a partial positive charge We indicated by Delta negative charge So this is why because of this two pole we call polar bonds and this is a cobalt bonds You can polar cobalt bonds. So Again, the Delta notation that we use here.

We kind of rely on which one is the more electronegative atom. So electrons are usually concentrated around the more electronegative atoms in the molecules and that electronegative atoms can say partial negative charge indicated by Delta minus and since electrons spend less time around the other atoms, so other atoms gain a partial positive charge that indicated by Delta positive. Another example here is the cobalt bond between iodine and chlorine.

Chlorine is more electronegative atom. So you have a delta negative charge on chlorine and delta positive charge on iodine. If you have a covalent bond between carbon and fluorine, so fluorine is more electronegative than carbon, so carbon will get delta positive charge and fluorine will get delta negative charge.

So that takes us to our next lecture problem here. It says use the delta notations to indicate which atom in each bond is more electronegative and then use an arrow to point towards the negative pole. If you look at this example here, carbon, chlorine, nitrogen, chlorine, and hydrogen, boron, oxygen, hydrogens. So if you want, you can pause the video and try to answer these questions on your own, and then you can check your answer with the answer I'm going to show you in a second.

If you have carbon-chlorine bonds, so carbon and chlorine, chlorine is more electronegative than carbon, so chlorine will get delta negative charge and carbon will get delta positive charge. Nitrogen fluorine case fluorine is more negative electronegative than nitrogen. So fluorine will get delta negative charge and nitrogen will get delta positive charge for hydrogen boron.

We have learned previously in the electronegative value chart that boron has electronegative values 2.0 and hydrogen is 2.1. So hydrogen is more electronegative than boron. So the hydrogen will have a delta negative charge and boron will have delta positive charge. OH case, so oxygen has a delta negative charge and hydrogen is delta positive charge because oxygen is more electronegative than hydrogen. So if you want to draw the dipole arrow, it will look like this.

It will start from carbon to chlorine. For this case, it will start from nitrogen to chlorine. For this case, it will start from boron to hydrogen. And for OH case, it starts from hydrogen to oxygen.

Now take us to our next lecture problem here, which of the following bonds has a dipole and for those that have dipoles on which atom to the first positive and first negative charge. If you look at these bonds here, carbon oxygen is two electronegative atoms. This is a polar covalent bonds.

For hydrogen and hydrogen, you have two same similar atoms. So this is a non polar covalent bonds. On hydrogen and fluorine case, this is also polar covalent bonds because two negative electro negative elements here two different elect two different atoms having different electronegative values for hydrocarbon and hydrogens carbon and hydrogen carbon has electronegative values 2.5 hydrogen has electronegative values is 2.1 carbon hydrogens bonds we know is the electronegativity difference is 0.4 therefore carbon hydrogens that bond is non-polar covalent bonds this is The thing that you must need to remember is not every time when you have a covalent bond having two different atoms and that bond would be a polar bond.

It's not true. For carbon-hydrogen case, it is a non-polar covalent bond. Only you can see the carbon and oxygen. That's a kind of polar bonds.

And for hydrogen and fluorine, this is also polar bonds. Again, the diatomic... and diatomic molecules and also the carbon hydrogen bonds are nonpolar covalent bonds.

That take us to our next lecture problem here identify bonds in the following by circling one for each. So we have here the bonds in hydrofluoric acid. Will that be ionic, polar or nonpolar covalent bonds?

If you want you can pause this video and then you can find the answer. or check your answer. The answer I'm going to show you in a second. So the bonds in hydroponic acid, so hydrogen and fluorine, this is two different elements and they have different electron negative values.

So it would be in polar covalent bonds. If you want to look at the bonds in fluorine, it's a diatomic molecule, same atom, so it's a non-polar covalent bond. The bonds in K2O, So you have metals and nonmetals combination that should be ionic.

You have bonds in CO. You have carbon and oxygen, two different electronegative atoms. It is not carbon-hydrogen bonds. Again, remember, carbon-hydrogen bonds is non-polar covalent bonds. That's the exceptional thing that you must need to remember.

But all other like carbon-oxygen, hydrogen-fluorine, nitrogen-carbon, so those are different elements, different electronegative values. those bonds would be polar covalent bonds. The bonds in O2, again, that's a non-polar covalent bonds.

The bonds in magnesium chloride, again, metal non-metal combinations and ionic bonds. And the bonds in NO, so nitrogen and oxygen, two different elements, different electronegative values, it would be polar covalent bonds. So that's how you have to identify whether the bond is polar bonds or is a non-polar covalent bonds or is an ionic bond. So that's all for this video. We'll talk about the organic chemical structure, how to draw the chemical structure for organic compounds in our next video.

Transcript for:Understanding Chemical Bonding in Organic Compounds

Transcript for:
Understanding Chemical Bonding in Organic Compounds