 So guys today we are going to start P block okay and in the P block boron and carbon we have already done in 11 standard. So here we are going to do nitrogen family group 15 so write down the heading okay. So group 15 we are going to start group 15 we are going to start and that is nitrogen family okay nitrogen family we also call it as these groups or these groups the element present in this group we also call it as Nectogens okay P N I C T O G E N S okay Nectogens okay so the elements which are present in these groups are we have Nitrogen N Phosphorus arsenic and Timony and Pismac these are the elements present in this group okay if you see the atomic number Nitrogen is 7 guys I love to meet you yourself Nitrogen has atomic number of nitrogen is 7 and then for phosphorus it is 15 atomic number for arsenic it is 33 then 51 and then 83 okay this is the atomic number we have if you see the difference here the difference that you are getting between nitrogen and phosphorus atomic number is here the difference is 8 and then it is 18 18 and the last one is 32 these numbers 8 18 18 32 these are the magic numbers magic magic numbers okay and this is true for all elements present in P block okay so advantage of these numbers are what if you know the magic number of P block element that is 8 18 18 32 you can find out the atomic number of any elements present load in the group down in the group because usually we know the atomic number of the first two or three elements okay suppose if you have to find out the atomic number of Bismuth you know this present in nitrogen family and if you know this for nitrogen you can add 8 18 18 and 32 you'll get it for this one that is the advantage of this magic okay so magic number for P block elements are 8 18 18 32 okay now when you find try to find out the electronic configuration of these elements suppose I am taking the simplest one nitrogen that is 7 the atomic number is 7 and hence the electronic configuration is 1 s 2 2 s 2 and 2 p 3 okay 1 s 2 2 s 2 and 2 p 3 okay ask me if you have any doubt okay both of you okay 1 s 2 2 s 2 2 p 3 correct so this you see this is the outermost electronic configuration 2 s 2 2 p 3 okay this nitrogen present in second period that's why the general electronic configuration of nitrogen is the outermost electronic configuration of nitrogen is 2 s 2 p 3 similarly for phosphorus the outermost electronic configuration is 3 s 2 3 p 3 then 4 s 2 4 p 5 s 2 5 p 3 like this okay so if I write down the general general outermost electronic configuration outermost electronic configuration this is for 15 group 15 it is n s 2 n p 3 n s 2 n p 3 where n is the period of that element okay okay n is the period of that element correct now you see in the outermost shell it has five electrons actually total five electrons so it needs actually three more electrons to gain its octet okay this electron is the electron present in the outermost shell and the number of electrons or those electrons which are present in suppose if I take this as this is suppose we have n x shell the outermost shell is nth then penalty then the cell which is just below this particular shell is n minus 1 okay so if n is the outermost shell n minus 1th the electron present in the electron in n minus 1th n minus n minus 2 2 etc are called are called inner electron not that important this term I am writing it out inner electrons and inner electrons does not take part in any bonding okay because the electron the interaction takes place always from the outermost electron and the other atoms okay so inner electrons does not take part in bonding at all okay but it plays a vital role when you have to decide the property of these elements right and this shell n minus 1th n minus 2 n minus 3 all this shell are the inner shell okay the shell which is just below the outermost shell which is n minus 1 is shell right the shell all these n minus 1 n minus 2 n minus 3 are the inner shell but the cell which is just below the outermost shell we call it as penalty mention this term you must you will see in the book okay it is penalty mention okay penalty mention okay the number of electron present in penalty mention that affects the property of these elements and all these things what I am discussing now it is true for not only for a nitrogen family it is true for oxygen group 17 group 18 everything okay so all those elements which has different different nature different different properties that is because of the number of electron present in outermost shell plus penalty mention and the size of the atoms okay so this thing is general thing that I am discussing now okay now if I talk about this group specifically okay as we go down the group there are few properties we need to understand here the first property you write down which is atomic radius atomic radius atomic radius what happens into that as we go down the group atomic radius increases because the electrons are going into higher you know shell next higher energy shell the electrons are going into that okay so that's why whenever the electron whenever you go down the group the atomic radius increases of these elements okay so write down here as we go down the group down the group atomic radius atomic radius increases okay so size down the group as you go the size increases okay that's a very important point we have and this trend is true for all other groups also it is true for group 16 group 17 group 18 okay so these properties that I am going to discuss now it is more or less true for all the elements all the other groups as well okay there are few exceptions here and there that we'll discuss when we'll do the specific groups separately okay so that is the one thing but in general you can understand this as we go down the group and that we all have already discussed in periodic table that down the group you go the atomic radius increases okay similarly if I talk about the metallic nature okay or first we'll discuss after this the ionic ionization enthalpy ionization enthalpy what is ionization enthalpy ionization enthalpy I won't give you the you know dictate you the in definition of this but ionization enthalpy is what it is the energy required to remove an electron completely from the outermost shell of an isolated gaseous atom if you want you can write it down ionization enthalpy is the energy required to remove an electron from the outermost shell to remove an electron from the outermost shell of an isolated gaseous atom so ionization enthalpy as we go down the group what happens then as we go down the group you know size increases right size increases so ionization energy decreases okay because the removal of electron is easier now as we go down the group as we go down the group ionization enthalpy decreases ionization enthalpy decreases okay right on the next time which is important here the ionization enthalpy of the elements of group 14 sorry of the elements of group 15 people of group 15 of the elements of group 15 is higher than is higher than that of is higher than to that of the corresponding elements of group 14 and 16 group 14 and group 16 due to due to half filled configuration due to half filled configuration okay this means what suppose you have a nitrogen correct and we are comparing carbon nitrogen and oxygen ionization enthalpy of carbon nitrogen and oxygen so carbon if you see the electronic configuration the outermost electronic configuration is 2 s 2 2 p 3 sorry 2 s 2 2 p 2 2 s 2 2 p 2 for carbon for nitrogen it is 2 s 2 2 p 3 and for oxygen it is 2 s 2 2 p 4 okay so you see here we have exactly half filled configuration this atom is more stable than the configuration is more stable than that of carbon and oxygen okay that's why the removal of electrons from nitrogen as compared to carbon and oxygen is difficult and when we see the ionization enthalpy of nitrogen it is more than to that of carbon and it is also more than to that of oxygen and I'm talking about ie 1 means first ionization enthalpy ie 1 correct usually the trend is what as we go left to right atomic radius increases or decreases left to right decreases why I got it I got it so there's a term I want to I wanted to listen and that is effective nuclear charge right they're defective because of effective nuclear charge the electron is going into the same shell right but the proton is also increasing by one and hence the effective nuclear charge is increasing if the electron is going to the different higher energy shell then that dominates the effective nuclear charge okay that's why the size increases down the group but here the reason is left to right if you go as we discussed the atomic radius atomic radius decreases atomic radius decreases correct the reason is write down z effective or effective nuclear charge that you must notice very important effective nuclear charge okay so when the size decreases so ionization energy should increase because when size decreases the removal of electron is difficult right so left to right if you go the ionization energy ionization energy increases the general trend is this but since it is you know organic chemistry so there are many exceptions into it general trend left to right ionization energy decreases but this is not true when we have this condition that is the electronic contrary half field configuration and it is true also when we have full field configuration there also it is true so here the change is this the expected order is carbon minimum then nitrogen and then oxygen oxygen should be even higher than that of nitrogen but here the extra stability due to half field configuration makes the ionization energy of nitrogen okay that is one very important point okay understood all of you yeah can I go to the next page