 Okay, there are a few reactions which are also important in this. We'll do that reactions also here. So for P4O6, P4O6, a reaction of this one or two reactions we'll discuss. P4O6, can you tell me the oxidation state of phosphorus in this molecule? The oxidation state of phosphorus is plus 3. This is one thing. Okay, now it is prepared by the reaction of P4 with limited supply of air. Okay, limited supply forms P4O6, limited supply of air. Few property are important. It is white colour, it is a white colour, vexist solid, vex kind of material it is. White colour, vexist solid, this is one thing. Soluble in ether, benzene, CS2, carbon disulfide, chloroform. Soluble in ether, benzene, CS2, chloroform. The reaction of P4O6 with water is very important. Okay, so with cold water you see, with cold water it gives P4O6 plus H2O, cold water. It gives phosphorus acid which is H3PO3, H2O is H3PO3. With hot water P4O6, 6 H2O, it gives H3PO4, 3 molecules of H3PO4, phosphoric acid plus pH3. So this molecule is phosphorus acid and this one is phosphoric acid, phosphoric acid. Okay, so this reaction is very important. They ask you this question, cold water and hot water, very important. Second one, phosphorus tetra oxide P4O8, P4O8, oxidation state plus 4, oxidation state of phosphorus is plus 4. And to get this, P4O6 is heated in absence of air, P4O6 is heated in absence of air around 200 or 210 degrees Celsius. 3 P4O8 we get here plus we'll get phosphorus red, it is also important. We get here phosphorus red. The important reaction of this is on hydrolysis of P4O8. P4O8, when you do the hydrolysis of this H2O, this gives phosphorus acid H3PO4 plus phosphoric acid H3PO4. Phosphorus, phosphoric both we get, H3PO3, I'll correct. It is H3PO3 and H3PO4. Phosphoric, both acid we get. All these are oxy acids of phosphorus, H3PO3, H3PO2, H3PO4. We'll discuss that also later, oxy acids of phosphorus, okay? Again, this one is important reaction. Last one we have is phosphorus pentoxide, that is P4O10, P4O10, phosphorus pentoxide. Oxygenation state is plus 5 of phosphorus plus 5. It is obtained by heating white phosphorus in excess of air. So, limited supply of air gives you what? Gives you P4O6, trioxide. If you have excess supply of air, 502 excess, then you end up getting P4O10. Most of the last pentoxide and trioxide, tetraoxide, they won't answer. These two are more important. Okay? Reaction of this P4O10 with water plus 6H2O gives 4H3PO4, phosphoric acid. The important property of this, write down, it behaves as an excellent dehydrating agent. Okay? So, suppose it reacts with acid reaction, we're assuming, 2HClO4 plus it reacts with P4O10. So, it removes water molecule from this, okay? And we end up getting Cl2O7 plus we'll get P4O10, a hydrated compound we'll get P4O10.H2O. Okay? So, it is a dehydrating agent also. It removes water molecule. All these three reactions you must remember. Okay? Now, the last compound of this, these elements are halides. Write down the next heading, halides, okay? These elements form two types of halide. The first one is trihalide and the second one is pentahalide. So, first we are going to discuss trihalide, which is Mx3 type, Mx3 type. Preparation is what? Elements directly combines with halogen to form trihalides, okay? So, we'll take excess of X, elements will take in excess, halides will take in limited way, right? So, we can write M, suppose we have M is the element here plus X2. So, it forms Mx3 trihalides of this. So, Mx3, so we have here 3, this is 2 and this is 2. Excess in these elements will take. Structures of halides are what? Mx3, it is similar to that of Mx3 type, Mx, X, X and a lone pair. This is also, so SP3 hybridized, similarly, SP3 hybridized, okay? Write down the trihalides, sorry, write on like this, the bond angle of the trihalides of phosphorus in bracket you write down or any elements. We are taking the example of phosphorus. The bond angle of the trihalides of phosphorus or any element increases with decrease in electronegativity, of halogen atoms, okay? So, if you have to compare the bond angle of PF3, PCL3, PBR3 and PI3, okay? The bond angle in PF3 is 98.5 degree. Again, this value you don't have to memorize. Here it is 100, here it is 101.5 and it is 102. So, like in case of hydride, if you see the central atom electronegativity increases, the bond angle increases, right? Here the outer atom electronegativity increases, the bond angle decreases. That also you can understand, okay? Outer atom, the electronegativity is less, right? So, bond angle is maximum, order is less, okay? Two, three properties we have for trihalides, write down, in short, just you write it down. All trihalides are covalent, are covalent. Next point, as we go down the group, the ionic character of these halides increases. Next point, among trihalides of nitrogen, like NF3, NCL3, NBR3 and Ni3, among trihalides of nitrogen, only NF3 is stable. All these are facts you must remember. Only NF3 is stable, NCL3 is explosive in nature. Next line, in this only next point to write down, next line, NCL3, NBR3 and Ni3 is unstable because of weak nitrogen halogen bond, and this is due to, and this is due to the large difference in size of nitrogen and hydrogen, nitrogen and halogen. Write down the Lewis basic strength of NX3. NX3, the Lewis basic strength is this. NF3 has minimum, then NCL3, then NBR3 and then Ni3. This is the Lewis basic strength of trihalides of nitrogen, and by this order we have Lewis basic strength is what? Tendency to lose lone pair, okay? So when electronegativity increases, then what happens? Tendency to donate lone pair will be less, that's what Lewis basic of NF3 is minimum, okay? This is the order of Lewis basic strength here, okay?