 The P block elements have some pretty interesting properties and in this video We are going to look at one such property briefly, which is the oxidation state Now briefly because honestly, this is a huge topic to study oxidation state And we will be able to do complete justice to it only when we study the individual groups in detail So what are we expecting from this video? Well, we will see how oxidation state varies across the P block and Why certain elements are more comfortable or stable in a particular oxidation state than the others? So to understand this, let's look at one of the groups of the P block Let's begin by looking at group 13 elements and their electronic configurations So what is common in the electronic configurations of these elements? Yes, they all have the same number of balance electrons That is two electrons in the s orbital and one electron in the p orbital That makes a total number of valence electrons in group 13 as 3 Now obviously because these elements have the same number of valence electrons or the outer electrons They also exhibit similar properties Now the reason I'm talking about valence electrons here is because it is closely related to the oxidation state And how is that? Well, you see oxidation state refers to the ability of an atom to undergo oxidation or reduction That is it is a total number of electrons that is gained or lost by an atom during a chemical bond formation Now when an atom loses electrons to attain stability, the oxidation state becomes positive And when it gains electrons to attain stability, the oxidation state becomes negative, correct? So coming back to a question, how is oxidation state related to the total number of valence electrons again? Well, you see the maximum oxidation state an element can show depends on the total number of valence electrons Now in the case of p-block elements, the total valence electrons is nothing but the sum of the s and p electrons, right? For example, if you go back to the group 13 elements again You will see that the maximum oxidation state any element in this particular group can show is a total number of valence electrons Which is nothing but the sum of the s and p electrons That's again 3, that means these elements will have to lose 3 electrons in order to attain a stable electronic configuration Now remember folks when we say lose or gain electrons to attain stability This is purely based on how oxidation state is defined as we know It is a hypothetical charge that we assign to an atom assuming that the atom forms only ionic bonds Now this is important because you see boron just as many other elements in the p-block does not lose electrons You know, it does not lose 3 electrons to form b3 plus ions. It actually shares as electrons But still while assigning an oxidation state We assume that the bonds that boron or any other atom forms to be completely Anic in nature and that it attains stability by gaining or losing electrons All right. Now that's enough recap about oxidation state Now coming back this maximum oxidation state for a particular group is also called its group oxidation state And every group has its own specific group oxidation state depending on the number of valence electrons As we just saw for group 13 it is plus 3 For group 14 it would be plus 4 because it has 2 electrons in the s orbital and 2 electrons in the p orbital For group 15 the group oxidation state would be plus 5 because it has 2 electrons in the s orbital and 3 electrons in the p orbitals And so on But you know what? All the elements within a particular group need not have only this particular group oxidation state In fact, p-block elements are known to have multiple oxidation states For example in group 13 the elements show plus 1 oxidation state In addition to the group oxidation state, which is plus 3 Similarly in group 14 the elements show plus 2 and minus 4 oxidation states in addition to the group oxidation state Which is plus 4 now can you think of a compound where carbon exists in minus 4 oxidation state? How about ch4? Yes in methane carbon combines with a more electro positive element like hydrogen and in this case Its oxidation state becomes minus 4 Whereas in a compound like co where it combines with a more electro negative element like oxygen The oxidation state of carbon would be a positive plus 2 Now if you look at group 15, can you name a compound in which nitrogen exists in plus 5 oxidation state? How about nitric acid? Yes in nitric acid nitrogen exists in plus 5 oxidation state Whereas in most amines or ammonia nitrogen exists in minus 3 oxidation state And just like nitrogen phosphorus also has many compounds in which it exhibits plus 5 plus 3 as well as minus 3 oxidation states So basically as you go across the periodic table or across the p-block the elements tend to show more number of oxidation states Now in contrast to s-block element, this is a very significant feature of p-block elements That is to show variation or variable oxidation states In s-block elements, we know that group 1 always shows plus 1 oxidation state Whereas group 2 elements always show plus 2 oxidation state But when you come to p-block, you will see that the elements tend to exhibit multiple oxidation states Now before wrapping up this video, I need to bring your attention to something peculiar here You see, it has been observed that the lighter elements in a group tend to show the group oxidation state Especially for group 13, 14 and 15 Whereas the heavier members within the group become more stable in their lower oxidation state By lower I mean the oxidation state that is two units lower than the group oxidation state For example, boron exists only in plus 3 oxidation state Which is the group oxidation state But the heavier member within the group thallium is more stable in plus 1 oxidation state Similarly, carbon, silicon, germanium, all of them show plus 4 oxidation state But let the heaviest member in the group is more stable in plus 2 oxidation state Just like that, if you look at group 15 Bismuth, the heaviest member exclusively exists in plus 3 oxidation state And not in the group oxidation state which is plus 5 So as you can see, all of these lower oxidation states are lower exactly by two units Correct? Now the question is, why does this happen so? Why are the heavier members more stable in a lower oxidation state unlike the lighter members? Now this can be attributed to something that we call the inert pair effect That mainly results due to the poor shielding effect of D and F orbitals So let's learn more about that in the next video