 We humans have been curious about ranking things. For example, we have ranking of our cricketers based on their scores. We have ranking of our superheroes based on their strength. So this should not be a surprise that we wanted to rank our metals depending on their reactivity. From most reactive metal to least reactive metal. And for this, we did some experiments and in this video, we are going to burn metals to rank them. Basically, if a metal burns vigorously or explosively, then it is going to be more reactive. Whereas if a metal burns weakly, then it's going to be less reactive. So let's do that. But before doing that, let's see what happens chemically when a metal burns in air. So we have seen earlier that if we take a shiny piece of magnesium ribbon and we burn it, then we are left with a white powdery substance. Now see what's happening here is the magnesium atoms, when they are burnt, they combine with the oxygen molecules present in the air and they form magnesium oxide, which is white in color. Mg plus O2 gives MgO. Now if we take another example like copper, which is also a shiny metal. And if we heat it in air, the color changes to black. Now what's happening here is that copper atoms, they are combining with the oxygen molecule of the air and forming copper oxide, which is the black color substance that you see. So as a general thing you can notice that when metals are being burnt or heated in air, their atoms combine with oxygen and form oxides. Whether you take aluminium or iron or sodium, most of the metals, they will combine with oxygen to form metal oxides. Most of the metals, almost all, because there are certain exceptions like gold and silver. See gold and silver, how much so ever you heat them, they are not going to combine with oxygen. We will not get oxides of silver and gold being formed. And that's why we say almost all metals combine with oxygen to form metal oxides. So with this, let's try to rank our metals according to how vigorously or how weakly they react with oxygen. So first let's begin with sodium. If you heat sodium in open air, it will catch fire and start burning very vigorously. We will have a vigorous reaction. In fact, this can even become explosive in nature. So be very careful while carrying out this reaction. In fact, we don't even need to heat it. Just keep it out in the open air and it might react automatically with oxygen and catch fire. That's why we never keep sodium in the open. We store it by dipping inside kerosene so it never comes in contact with air or water. And just like sodium, potassium is also very reactive. Its reaction with oxygen is also very vigorous in nature. So these are the two top most reactive metals that we have. Next we have magnesium. We have already seen that when we burn magnesium, it catches fire and it burns with a dazzling white flame. So it is also very reactive, but in comparison to sodium and potassium, it can only come second. It's no match for them. Now next up, I have metals such as aluminium, zinc, iron and copper. Now all of them react in a similar fashion with oxygen to form their oxides. And that's why I have grouped them together in a single box. It's pretty hard to actually tell which one among them is more reactive. And their reaction is not as vigorous as sodium or magnesium. And that's why I've put them at a third rank. Now even among them, aluminium, zinc and iron, they will burn and react with oxygen to form their oxides. Whereas copper, it does not burn. It will get hot and then it will react with oxygen to form copper oxide, whose colour is black. And that's why you will see a colour change from copper colour to black colour. Okay, with this, I have listed out few of the metals that will react with oxygen to form oxides. Now after this, we have metals such as gold and silver. Now these two metals, on being heated up, they do not react with oxygen. Doesn't matter how much so ever you heat them, there will be no reaction happening. That's why these metals are called noble metals or peaceful metals. These are the least reactive in our list. So this is our list of reactivity. Here the metals, sodium and potassium are most reactive. Then we have magnesium. Then we have these metals, aluminium, zinc, iron and copper. We are not sure which one is more reactive among them. And then at last we have gold and silver. Now before we wrap up the video, let me tell you one interesting fact. See few of these metals, they can react with oxygen and form oxides, even at normal temperature, without being heated up. For example, if I take a piece of aluminium metal and I leave it outside for some time. Now the outer most atoms, the ones that are in contact with air, they can react with oxygen and form oxide, even at room temperature, even at normal temperature. Something like this. And they will form a protective layer, a layer of oxide over this metal. So what will happen is, this layer will prevent the inner most atoms from reacting with oxygen. Because now oxygen cannot go through it and come in contact with the inner most atoms. So in one sense we can say that the outer most layer, it sacrifices itself by reacting with oxygen and therefore it prevents or safeguards the inner most atoms from reacting with oxygen. And this happens with many metals like magnesium, zinc, sodium, they all will have a layer of metal oxide on top of them. In this video, we wanted to rank the metals in the order of their reactivity. For this, we reacted the metals with oxygen and let them form oxides. Now depending on how vigorous the reaction was, we put them in this particular order. But there was a problem with this particular process. See, we did not get a detailed enough list. For example, if you look at position number three, we have four metals clubbed for this particular position. We can detail them further enough, right? Over here, we have two metals grouped together. Over here, we have two more metals grouped together. So for this purpose, we will be carrying out more reactions in future videos. We will be reacting metals with water, we will be reacting metals with acid and with more information, we will be detailing this list out.