 In this video, we are going to look at some of the anomalous properties of nitrogen. The properties that make nitrogen different and unique from the rest of the group 15 elements. You see, nitrogen literally is 70% of her atmosphere. It is extremely inert in nature and yet nitrogen when combined in the form of ammonia is one of the most useful substances in the world. In fact, figuring out a scalable way to make the inert nitrogen react to form ammonia was one of the greatest challenges of the 20th century. And thanks to Haber's process, we have now no worry regarding the production of ammonia. Now coming to the chemistry of nitrogen, nitrogen differs from the rest of the members in a number of ways, such as it has small size, high electronegativity, high ionization enthalpy, exhibits multiple oxidation states, and it has the unique ability to form strong p-pi-p-pi bonds and also compared to the others, nitrogen has no empty d orbitals available. But what are the consequences? How do these properties affect the chemistry of nitrogen? Let's see. Because of its small size and high electronegativity, nitrogen has the unique ability to form hydrogen bonds. This is why ammonia forms hydrogen bonds whereas the larger, less electronegative phosphorus has no such possibility. That is, phosphine does not form any hydrogen bonds but ammonia forms. Now coming to ionization enthalpy, due to its large ionization enthalpy, nitrogen cannot lose its valence electrons easily and therefore prefers to form covalent bonds. Just like that, the ability to exhibit multiple oxidation states actually makes nitrogen pretty versatile. For example, these are the oxidation states of nitrogen in different compounds. So let's now talk about how nitrogen forms strong p-pi-p-pi bonds and how it affects its chemistry. You see, just like carbon of group 14, nitrogen has the unique ability to form p-pi-p-pi bonds with itself and with elements that are similar in size and have high electronegativity like carbon and oxygen. For example, nitrogen can combine with itself to form diatomic nitrogen molecule. It can combine with carbon to form cyanide ion. It can combine with oxygen to form nitrosonium ion as you can see here. Now in the case of diatomic nitrogen molecule, as you can see here, we have a triple bond just like the others and this triple bond is formed by 1 sigma and 2 pi bonds where the sigma bond is formed by the head-on overlap of the 2 sp orbitals whereas the 2 pi bonds are formed by the parallel overlap of the unhybridized p orbitals. And as a result of the strong p-pi-p-pi bonding, its bond enthalpy is also very high. That is the bond enthalpy of diatomic nitrogen is very high and this is what it makes nitrogen molecule inert at room temperature. Now even though nitrogen is inert at room temperature, we can activate it or make it more reactive by increasing the temperature and this is something that we exploit easily in the Haber's process where we force our inert nitrogen to combine with hydrogen and form ammonia using conditions like very high temperature of 700 Kelvin and high pressure. In fact when you increase the temperature, nitrogen can react directly with various elements and even some transition metals. Now the interesting thing to note here is that even though all of them have triple bonds, it is only nitrogen that is inert at room temperature whereas CN minus and NO plus are more reactive than nitrogen and this is because their bonds are more polar. CN minus and NO plus are more polar due to the electronegativity difference between nitrogen in carbon and nitrogen in oxygen. Now coming back to nitrogen, this evolutative form strong p-pi-p-pi bonds makes nitrogen very special because unlike nitrogen, the residue members cannot form these bonds. This is because as you go down the groove their atomic size increases right and their atomic orbitals are much larger or more diffused than nitrogen and that means they cannot form effective overlapping as you can see in this case and this is why all the other members form single bonds whereas nitrogen forms triple bonds and if you look at a single bond of nitrogen it is extremely unstable. You see nitrogen atom is really very small and when it forms a single bond the non-bonding electrons are too close to each other and they repel each other very strongly and this inter-electronic repulsion is what makes nitrogen single bonds extremely thermodynamically unstable. So if you extend this, if the single Nn bond is not strong enough or stable enough, it would consequently affect its catenation tendency, right? Exactly. Because of the weak Nn bonds, nitrogen actually has a very poor catenation tendency. Now I thought we could discuss one more property which is the unavailability of deorbitals in nitrogen but looks like that would make this video very heavy to comprehend. So let's discuss that in a short video next.