 In this video we will explore how the inert pair effect influences the type of bonding in group 14 elements. To be more specific we will see how inert pair effect favours the formation of ionic bonding in heavier elements like lead. Now we know that inert pair effect describes the reluctance or the inertness of the ns electrons to participate in bonding and this happens because of the poor shielding effect of the intervening d and f orbitals and it becomes more pronounced as we go down the group. That means it's going to be more significant for lead. Inert pair effect also describes why lead is more stable in the plus 2 oxidation state whereas all of the other group 14 elements are more stable in the group oxidation state which is plus 4. Now the question is do you think that the inert pair effect can play a role in dictating the type of bonding as well? Well indirectly may be yes because depending on the oxidation states we know we can predict the type of bonding right? For example all of the elements of the group 14 in the higher plus 4 oxidation state would prefer covalent bonding whereas the lead which is more stable in plus 2 oxidation state would prefer anic bonding. Now that would be correct because based on Fajans rule we know that lower valencies always prefer the formation of ionic bonds whereas higher valencies which in this case is plus 4 would prefer the formation of covalent bonds right? But suppose we didn't know about Fajans rule. Is there a way to substantiate this preference in bonding using the inert pair effect? Well that's what we're going to try in this video. Okay so to figure out the answer to this let's consider two elements of group 14. One is lead and one is carbon that is one in which inert pair effect is acting and carbon in which no such thing is going on. Alright so let's look at carbon first in detail. So you see carbon has four valence electrons in 2s and 2p orbitals. Now because it is small size of carbon and its high ionization enthalpy carbon will not want to give away all of these four electrons you know carbon will not form C4 plus ions it's extremely unstable and the ionization is required to form this is also extremely high so what does it do? It would rather prefer to share these four electrons. Now for that one of the 2s electrons will get excited or promoted to the empty 2p orbital and this gives us four unpaired electrons which can hybridize and combine with other unpaired electrons to form four covalent bonds. So here we have the example of methane CH4. Because the 2s and 2p orbitals are closed in energy it is easy to excite the 2s electron into the empty 2p orbital and notice that energy required for this promotion is more than compensated by the energy released when forming the two extra covalent bonds. Now can we do something similar in the case of lead you know excite the 6s electron and form covalent bonds like this? So pause the video here and think about it for a moment okay? Okay let's see. In heavier elements like lead the inert perifet comes into play so what happens here is that the valence 6s and 6p electrons get drawn closer towards the nucleus that is they experience greater effective nuclear charge due to the poor shielding effect of the F and D orbitals. Now this affects the valence s electrons more than the p electrons that is 6s experiences more nuclear charge so because of this the energy difference between 6s and 6p is larger than we would normally expect and it's definitely larger than the energy difference between the 2s and 2p orbitals of carbon. So that means promoting the 6s electron would require more energy and even if we somehow excite the 6s electron to the empty 6p orbital the resulting covalent bond formed does not release enough energy to compensate or may not compensate for the energy required for this promotion. Unlike in the case of carbon where the bonds formed are strong enough to encourage the promotion of the 2s electron. Now why are these bonds not as strong as the carbon bonds? Obviously look at the size right lead is a much bigger atom and as the atomic size increases atoms form longer and weaker bonds and this decreases their bond energy. Thus as carbon form stronger bonds than lead it is worth exciting or promoting this 2s electron to the 2p orbital as compared to exciting the 6s electron to the empty 6p orbital. So what happens is instead lead would rather let go of the 2p electrons easily and form pb 2 plus ions. Now this formation of pb 2 plus is also favored by the low ionization enthalpy. You see the ionization required to knock off these 2 electrons is much lower. Now because the s electrons would rather prefer to remain paired they are reluctant you know to participate in any kind of bonding be it ionic or covalent. Now remember folks this does not mean that lead forms only ionic compounds. No here we are simply talking about the role of inert pair effect in understanding why lead refers to form ionic bonds over covalent bonds. For example pb Cl4 is a covalent compound whereas pb Cl2 is considered to be predominantly ionic in nature. So here lead is in plus 4 oxidation state and here lead is in plus 2 oxidation state right and we know that because of inert pair effect lead is more stable in plus 2 oxidation state and because of that at room temperature pb Cl4 easily decomposes to form pb Cl2 and chlorine gas and in this process it acts as an oxidizing agent. So let's learn more about that in the next video.