The learning objective of the topic is explain the relationship between the type of bonding and the properties of the elements participating in the bond. So what is a bond? What types of bonding we are talking about and what is the relationship between the bonding and the elements?
So we will be talking all of this in this video. Hello everyone this is topic 2.1 types of chemical bonds. This is taken from AP Chemistry college board. Let's start. So what is a chemical bond?
Chemical bonds are forces that hold atoms together to make compounds or molecules. So in chapter 1, I have told you what is an atom, what are compounds and what are molecules. Atoms basically combine together to form compounds and molecules.
So what is the force that keeps the atoms together? That force or you can say that attraction is called a chemical bond. So chemical bonds are basically of three types, iron, covalent and metallic.
I'll be talking all of these types in this video. So let me start with the basic property which is electronegativity. This property is responsible for formation of the bonds between two atoms. So what is electronegativity? Electronegativity is the measure of the tendency of an atom to attract electrons towards itself.
So a bond is formed between two atoms. Suppose there is atom A and atom B. there are electrons which are present for the warning. So these electrons when they are attracted towards one of the atoms, it means that that atom has high electronegativity.
In a periodic table, electronegativity decreases as we move down the group and electronegativity increases as we move from left to right in a period. When we move down the group, the size of the atom goes on increasing. So electrons become far away from the nucleus and there is less attraction between the nucleus and the outermost electrons.
So that is why the electronegativity decreases as the size increases. Whereas when we move from left to right the size of the elements goes on decreasing and that is why the electrons stay near to the nucleus and the electronegativity increases. Electronegativity is basically due to the structure of the atom, the shell model and the Coulomb's law. If you want to know more about these factors, you can watch video of topic 1.5.
But what are the values of the electronegativity? Here you can see the values of the electronegativity of all the elements of the periodic table. You can see here that on the left of the periodic table, the values of electronegativity is quite low and on the right side of the periodic table, the electronegativity values are very high. Out of all the elements, fluorine has the highest electronegativity.
Now, on extreme left of the periodic table these elements try to lose the electrons to attain a noble gas configuration that is why these elements have lesser values of electronegativities while on the right side of the periodic table except the noble gases so these elements try to gain the electrons to attain a noble gas configuration and become stable that is why here you can see the values of elements is quite high The group 1A elements have one valence electron, group 2A elements have two valence electrons and so on. Here group 7A elements have seven valence electrons and group 8A has eight valence electrons except helium. These elements are having fully filled orbitals while rest of the elements do not have fully filled orbitals.
So to have that fully filled orbitals, these elements lose the electrons and these elements gain the electron. So if lithium loses the electron, that electron can be gained by fluorine to have 8 electrons in total and to become stable. This losing and gaining of the electrons leads to the formation of the ionic bonds. But it is not necessary that all the elements would form bonding by gaining all and losing the electrons. Because here you can say that if hydrogen has 1 electron and fluorine has 7 electrons, then Hydrogen will lose that one electron and fluorine would gain that one electron and a bond would be formed between hydrogen and fluorine.
It is not always the case. There it depends a lot on the electronegativities. So if there is a lot of difference between the electronegativities then only gaining and losing takes place.
But they if there is not much difference in the electronegativities then the sharing of electrons takes place. So let's see more of this by talking about ironing compounds and covalent compounds. Here you can see that sodium has one valence electron and chlorine has seven valence electrons. So sodium loses one valence electron to attain noble gas configuration and it becomes Na positive. similarly on right side this chlorine atom gains that one electron and attain a noble gas configuration or you can say fully filled orbital and it becomes chloride and there is an attraction between the sodium ion and the chloride ion this kind of interaction is called an ionic bond so sodium chloride is formed which is an ionic compound ionic compounds are the compounds which is made up of ions as here it is made up of sodium ion and chloride ion that form charged particles when an atom gains or loses the electrons.
Here sodium atom lost one electron and chlorine atom gained that one electron and that is why NaCl is formed which is an ionic compound. Second type of bond is a covalent bond. A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms.
Earlier ionic bond was when the elements gains or loses the electrons. Here covalent bond is sharing of electrons. So if similar type of elements or the elements that have almost the same electronegativity value when they come close to each other a covalent bond is formed.
For example hydrogen atom has one valence electron so when two hydrogen atoms will come close to each other they will share one electron each and both of them will have two electrons in their shell. That will make it stable and a bond would be formed between two hydrogen. The covalent bond which is formed between two elements when there is not much difference in the electronegativity, that is called nonpolar covalent bond.
But when there is a large difference in the electronegativity, then a polar covalent bond is formed. A polar covalent bond is the bond when the shared pair of electrons are not shared equally. There are two elements, one is hydrogen atom and one is fluorine atom.
Hydrogen atom has 1 electron and fluorine atom has 7 valence electron. So when hydrogen and fluorine come close to each other, they form a covalent bond between themselves. But fluorine being more electronegative than hydrogen, it attracts the shared pair of electrons towards itself as you can see here.
The shared pair of electrons is not equally distributed between the elements. They are towards only one element. This leads to formation of a partial charges on both the elements.
As you can see here. the hydrogen has developed a delta positive charge which is partial positive charge and the chlorine atom has developed the delta negative charge which is said as partial negative charge so the elements when they have a higher difference in the electronegativity it leads to polar oval and one so let's see some more examples of polar and nonpolar compounds for polar we can see that hydrogen and chlorine there is a polar oval and one between them so hydrogen being less electronegative than chlorine has developed a delta positive charge and the chlorine has delta negative charge another example is water that is h2o so oxygen is bonded to hydrogens and both the hydrogens have the delta positive charge and oxygen has the delta negative charge because of the difference in the electronegativity cylinder is the case for the ammonia that is nh3 nitrogen gets a delta negative charge and hydrogens get the delta positive charge Let's see some examples for the non-polar covalent bond. These are mostly when they are the same elements or there is not much difference in their electronegativity.
For example, nitrogen molecule where NN triple bond is formed and this is a non-polar covalent bond. Another example is carbon dioxide CO2 or CCL4. Now we know that in a polar covalent bond, the share pair of electrons are towards the more electronegative element. Now let's see the comparison here.
Hydrogen is forming polar covalent bonds with all the halogens here. First case is fluorine, second case is chlorine, then third case is bromine and the fourth case is iodine. For all these four cases, the electronegativity values are written at the top. As I told you, the electronegativity decreases as we move down the group.
So the fluorine has the highest electronegativity and the iodine has the lowest electronegativity out of all the halogens. So when shared pair of electrons are attracted towards the halogens, there is a dipole formed. This arrow with a cross sign shows the dipole of the compound.
This shows that the electrons are more towards the fluorine and the hydrogen has a delta positive charge. And the difference in the electronegativity for hydrogen, iron is lowest and hydrogen and fluorine has the highest difference in the electronegativity. That is why the dipole moment for HF is highest and HI is the lowest.
There is one more property which tells about the type of bond so that is the metallic property a bond which is formed between metal and non-metal will be an ionic bond and bond which is formed between two non-metals is always a covalent bond so for ionic bond you can see that sodium is a metal and chlorine is a non-metal so there is an ionic bond between sodium and chlorine next example is potassium and chlorine so potassium is a metal and chlorine is a non-metal so this bond would also be an ionic bond similarly for co2 and MgNO3 whole twice. There is an ionic bond between magnesium and nitrogen atoms. So magnesium is a metal and nitrogen is a non-metal and covalent bond is bond between hydrogen atoms. Both the hydrogen atoms are non-metal, both the oxygen atoms are non-metal, then carbon and hydrogen are non-metal. So methane also has covalent bond and all the organic compounds are also have the covalent bond because all the elements in an organic compound are non-metal.
Water is also an example for the covalent bond because hydrogen and oxygen are also nonmetals. So basic thing is the difference in the electronegativity is not the only factor which tells that the bond is ionic or covalent. Metal and nonmetal property also tells that the bond would be ionic or covalent.
So these properties should be kept in mind while we characterize a type of bond. Last type of bonding is metallic bonding. So the metallic bonding is found in metals and their alloys when the atoms give up their valence electrons they form ions and these ions are held together by the electron cloud surrounding them the electrons are surrendered to a common pool and they become shared by all the atoms in the solid metal so this provides the property of ductility to the metals and the cloud of free electrons is highly mobile and that results in good electrical conductivity in the metals So the learning objective of the topic was explain the relationship between the type of bonding and the properties of the elements participating in the bond. So the properties which we talked about for the bonding are electronegativity and the metallic property. And apart from that, we studied the types of the bonding, the covalent bond, the ionic bond and the metallic bond.
And we saw that how these types of bondings are related to the properties of the elements. Please like and subscribe to the channel LogIota. and press the bell icon