 In this video, we will talk about the trends in the standard electrode potentials of the transition elements, specifically m2 plus slash m and m3 plus slash m2 plus electrode potentials. That is how easy it is for the transition metals to go from m2, m2 plus state and similarly from m2 plus to m3 plus oxidation state. Now if you look at it, we can see that the standard electrode potentials or the trends should be more or less an extension of the stability of the oxidation state. If a metal attains a more stable state, easy will it be for it to undergo that particular change or transformation and that means more negative will be the electrode potential. And in contrast, if you see a positive value for a specific electrode potential, then that means that particular change or that particular oxidation state is not really favored. So what does the trend say for our 3D series elements? Well we can see that as we move across a 3D series, the standard electrode potentials become less and less negative. We start from minus 1.63 and kind of end with minus 0.76 right? That is as we move across the period, the values become less and less negative. Now this is related to the increase in the sum of the first and second ionization enthalpies. However as you can see, there are a couple of exceptions. For example, copper has a positive electrode potential. Similarly manganese, nickel and zinc have slightly more negative values than what is expected. So how can we justify these exceptions? So that we need to look at their electronic configurations. When manganese becomes MN2 plus, the electronic configuration changes from 3D5 4 is 2 to a more stable 3D5 configuration, which is more stable due to the half electronic configuration right? So this is why this particular change is favorable because it attains a more stable state and because of this, the standard electrode potential also becomes more negative. Similarly, in the case of zinc, ZN2 plus results in a more stable fully filled 3D10 electronic configuration and because of this again, the standard electrode potential becomes more negative than what would be expected. But what about nickel? ZN2 plus 2 state, the electronic configuration of nickel is still argon 3D8 right? It does not attain a stable half filled configuration or a fully filled D10 configuration. So why does the electrode potential become more negative in this case? Well the reason here is slightly different. You see nickel has a very small size and has a very high hydration enthalpy and as a result more energy is released when it bonds with water molecules making the electrode potentials more negative than what would be expected. Copper, unlike the other transition elements of the series, has a positive standard electrode potential. Now to understand why that happens, we once again have to look at the electronic configuration. Now the electronic configuration of copper is argon 3D10 4S1. Now in order to form Cu2 plus iron, it would have to lose electrons from the 4S orbital as well as disrupt the highly stable 3D10 orbital right? In the case of Cu2 plus iron, we ended with an electronic configuration of 3D9. So this transition from a more stable 3D10 state to a less stable 3D9 makes it highly undesirable and as a result the standard electrode potential becomes positive in the case of copper. Now this unique behavior is also why copper is unable to displace hydrogen from acids. In fact only highly oxidizing acids like nitric acid or hot and concentrated sulfuric acid can react with copper and oxidizer. So as you can see the amount of energy required to convert copper to copper 2 plus ions is not compensated by its hydration enthalpy. Now this is quite opposite to the case of nickel where we saw that the formation of 3D8 state is stable or stabilized by the high hydration enthalpy of nickel. Let's now look at the trends in the standard electrode potential of M3 plus slash M2 plus. That is how easy it is to attain M3 plus state from M2 plus state for the transition elements. Now the trend in this case is not very straightforward. It shows a very erratic or a varying trend. For example in the case of Scandium, it favors going from plus 2 to plus 3 state as Scandium 3 plus attains a stable noble gas electronic configuration. And this is why it has a low value of standard electrode potential. Now if you talk about zinc, the transition from plus 2 to plus 3 state is not very favored because this disturbs a highly stable 3D10 electronic configuration. As Z n 3 plus attains a less stable state, the standard electrode potential in this case would be high. Let's look at another example, say manganese. Here again quite similar to zinc, manganese does not favor the formation of Mn3 plus state. As it forces manganese to go from a more stable 3D5 electronic configuration to a less stable 3D4 state. And this is why manganese again has a comparatively high value of standard electrode potential for this particular change. Whereas in the case of iron, this change is favored because FA3 plus results in a more stable 3D5 electronic configuration. Now we can invariably relate the standard electrode potentials with the chemical reactivity of transition metals. Except in the case of copper which has a positive value for standard electrode potential, the metals of the 3D series are more reactive and can be oxidized by acids. Another example, ions like titanium 2 plus, vanadium 2 plus and chromium 2 plus act as strong reducing agents and can liberate hydrogen from dilute acids. On the other hand, Mn3 plus and CO3 plus act as strong oxidizing agents in aqua solutions.