 In this video, we will find out the trends in the ionization enthalpies of transition elements. We know that, in general, ionization enthalpy increases as we move across the periodic table. Something similar happens in the case of transition elements as well. With increase in nuclear charge and with the D electrons getting successively filled, the ionization in general for transition metals show an increasing trend, as you can see here. However, there are a few exceptions. For example, vanadium and chromium show slightly lower values than their predecessor. Similarly, towards the end of the series, cobalt nickel and copper also show slightly decreasing values of ionization enthalpy. But again, you can see that the variation is not very drastic or as significant as we observe in the case of S or P block elements. So, in general, although we can say that the ionization enthalpy values increase along a period, the trend as such you can see is erratic or irregular. Further, you can see that in the first series, zinc has the highest ionization enthalpy. And it's not as unique to zinc. Zinc, cadmium and mercury all have highest values of ionization enthalpies in the respective series. This is because of the completely filled detent electronic configuration. As we need to provide more energy to break this stable arrangement, the ionization enthalpies of these elements is very high. Let's now look at the trends in the second and third ionization enthalpies. Here again, we can notice a couple of interesting things. Firstly, when you compare the first ionization enthalpies with the second and third, you can see that the magnitude of increase in the values of second and third ionization enthalpies is much larger or much higher than the first ionization enthalpies. Now, if you look at the second ionization enthalpy values, you will see that chromium and copper have abnormally higher values than we would normally expect. I mean, if you look at the values here, you can see that they definitely stand apart from the rest of the elements in the series, right? Similarly, if you look at the third ionization enthalpy values, here again, we note an exceptionally high value in the case of manganese. Now, can you figure out the reason behind these exceptions? Well, let me give you a clue. All you need to do is simply look at their electronic configurations, okay? So, keeping that in mind, pause the video and try to find out the answer. So, as I said, it all comes down to the electronic configuration. Now, if you look at chromium, we know that the electronic configuration of chromium is argon 3D5 4S1. And when it loses one electron, it gets a very stable electronic configuration which is 3D5. So, that means to form CR2 plus ions, we need to disturb a highly stable state here. And that's not very desirable for chromium. Similarly, in the case of copper, CU plus gives it a very stable configuration where it has completely filled D10 orbitals. It's not very excited to form CU2 plus ions because that again disturbs the stable arrangement. And this is why we need to provide more energy to break these stable electronic configurations, which is the reason that their second ionization enthalpy values are substantially higher. We can extend the same logic to manganese as well. In the case of manganese, MN2 plus to MN3 plus transition demands a high supply of energy. This is because manganese is forced to move from a highly stable 3D5 electronic configuration to a less stable state which is 3D4. As a result, the third ionization enthalpy value of manganese is very high. So, that majorly covers what we need to know about the trend in the ionization enthalpy values. Now, we know that ionization enthalpy values are closely related to the stability of the oxidation states. A high value of ionization enthalpy would mean that that particular oxidation state is not really favored. For example, the third ionization enthalpy value of copper, nickel and zinc is very high. And this means that it is generally difficult for these elements to form plus 3 oxidation state. But once again, in deep block elements, it would be wise not to make any generalizations like that. Instead, let's learn more about oxidation states in the next video.