 So, this is the first group we have, even hydrogen is also placed in this group only. If you look at the elements of these groups, we have hydrogen, lithium, sodium, potassium, rubidium, cesium and franzium. These are the elements we have, right? These are metals also. S-block elements are good metals. If you go left to right in a in a pre-order table, the metallic properties or metallic nature decreases. Metallic nature is nothing but the tendency to lose electron, okay? So few properties you should understand, which is common in all the groups, okay? You will see here, whatever, you know, few properties you will see in alkali metals here, that also goes through, like, no, that is also true with the alkaline earth metal, which is group 2 elements, correct? So, we try to understand first few general things here. Like, you see, if you talk about the elements here, why these elements are placed in group 1? And why we are calling it as S-block elements? How do we define blocks? Incredible? Any idea? How do we define different different blocks? Why do we place sodium in S-block? Why not in P-block? See, when you draw the electronic configuration of any elements, synthetic resins, we don't discuss here, should this? It is a little bit as therein polymers chapter, which also they have removed, okay? That's why we are not discussing synthetic resins over here, okay? Well, it's electron and that's in S-subtial, right? So, for any elements you see, if you look at the electronic configuration, like, for example, if I take boron, boron is the first element of P-block, correct? Electronic configuration is 1S2, 2S2 and 2P1. So, if the last electron goes into P-subtial here, that's why it is the P-block element. So, how do we define a block and how do we place an element in a given block? It depends upon where the last electron for that particular element, you know, where it goes, the last electron, where it goes, in which sub-shell or in which shell it goes, right? So, if the last electron goes into S-subtial, it is said to be an S-block element. Same goes with P-block and D-block also, okay? So, for all these elements you see, there is one pattern that you need to understand. There is, you know, for all these elements you see, last electron, it goes into S-subtial, okay? If you look at the configuration here, electronic configuration, I will show you, hydrogen has only one electron, right? So, its configuration is 1S1. It has three electrons. So, it is 1S2, 2S1. It has 11 electrons. So, it is 1S2, 2S2, 2P6, 3S1. Similarly, for potassium, rubidium, cesium, and frangium. Is this atomic number correct? Yeah, 3S1. So, if you look at the electronic configuration, this we can also write as helium, 2S1. Or this one is neon, 3S1. This one is argon, 4S1. This one is krypton, 5S1. If you have this, it is xenon, 6S1. And the last one is radon, 7S1. So, for all these elements you see, the electronic configuration, the last electron goes into S-subtial and hence it is S-block elements, right? And since we have, we can have only two electrons in S-orbital, right? That's why we have only two groups in S-block, group 1 and group 2. Because we can have only two possible configurations. Either we can have S1 or we can have S2. So, group 1 has S1 configuration, outer motion, and group 2 has S2 configuration, outer motion, right? Outermost, right? So, this is how we, you know, place or, you know, define the blocks of a given element. Okay. Now, if you look at this electronic configuration, the general electronic configuration of the elements of group 1, general electronic configuration, you can say it is NS1, outermost, sorry, outermost electronic configuration, NS1, then N is the period of the element. N is the period of the element. Any doubt in here? How do we define alkali metals? We define alkali metals as, this is the metals which reacts with, metals which reacts with water and forms, and forms hydrogen gas, H2 gas, like, which reacts with water and forms hydroxide, liberates hydrogen, are said to be alkali metals. Hydrogen does not react with water, right? Hydrogen does not react with water. Hence, hydrogen, however it is placed in group 1, it is not considered as the alkali metal. So, out of all these you see, this is the first element here we have, hydrogen, it is not an alkali, an alkali metal. If you look at the difference here, it is 2, 8, 8, 18, 18 and then 32. This number 2, 8, 8, 18, 18, 32 you all know, this number is called this number is called magic number for group 1, okay? Magic number for group 1. If you know these numbers, you can find out the atomic number of any lower elements belongs to this group. Then, yes, finished. Now, you look at the properties of these alkali metals. The first one, right down, atomic and ionic red eye, sorry. Yeah, tell me, what is the trend for this 2 we have? What happens as we go down the group? Yes, atomic radius and ionic radius increases down the group. The reason is what? So, write down, write. So, first of all, write down here, write down. As we go down the group, as we go down the group, the radius, whether it is atomic radius or ionic radius, the radius increases. Obviously, we have poor shielding effect, but as we go down the group, one extra shell is getting added, right? After 1s, we'll get 2s, then we'll get 3s, 4s, 5s. So, you're going away from the nucleus, right? Like this. Like this. We're going away from the nucleus, correct? Hence, the size increases. So, write down, as we go down the group, as we go down the group, atomic and ionic radius increases because of less effective nuclear charge and due to the addition of one extra shell due to the presence of, due to the presence of an extra shell, done? Right? So, based on this information, we can have 2, 3 property you can understand here. Like you see, size is increasing right down the group. So, we have this first, then it becomes this, then it becomes this, then it becomes this, and so on. Right? Like this. So, if you talk about the ionization energy, so as we go down the group, what happens with ionization energy? Could you tell me? Ionization energy decreases. And why it decreases? Yeah. So, what we can say here, you see clearly you can understand that as you go down the group, the size is increasing. So, distance of the center and the outermost electron also increases. Right? You see this? It increases. Okay? So, as the distance increases, it is easier to take the electron out. Means, it requires lesser energy to break this attraction pool so that the electron comes out. Right? So, first thing is what? With size, we can relate ionization energy when we say as size increases, ionization energy decreases. Ionization energy decreases means tendencies to lose electron is more. Correct? Means, electropositive character increases. Means the metal converts into an electropositive ion. So, it has more tendency to release electron means more electropositive nature. Right? And as the electropositive character you know increases, tendency to become more electropositive is more. It means it is releasing electron, then only it is becoming as you know more electron releasing, more electron releasing nature it is. Right? So, hence as we go down the group, the electropositive character tendency to forms the positive ions that also increases since ionization energy decreases. So, to tendency to form electropositive ions also increases which we call it as electropositive character. Right? So, electropositive character increases. If you talk about the metallic nature down the group the metallic nature you know increases again the same reason size increases attraction is more. Right? A side attraction is less hence the world of electron is easier and hence it has more tendency to form the electropositive ion and more tendency to release electron. More tendency to release electron means more ionization, sorry less ionization energy. So, with this we can relate two three properties here. The first one is right down ionization energy, ionization energy. Right down quickly as we go down the group as we go down the group as we go down the group size increases ionization energy decreases. So, I'll write down this way. Here we have sorry and when I write ionization energy it automatically it means you're talking about first ionization energy. Ionization energy decreases means metallic character metallic character increases electropositive nature also increases. Next write down third sorry yeah third property is if you talk about the oxidation state only one possibility is alkali metal always shows alkyl metal always shows plus one oxidation state okay plus one oxidation state any compound if you see Na2SO4 NaCl right NiCl any example you can do. Okay the next one is hydration energy what is hydration energy anybody what is hydration energy what is the difference between solvation energy and hydration energy is there any similarity or is there any difference between solvation energy and yeah that's right okay see whenever you dissolve with you dissolve a compound into any solvent any solvency right dissolution generally is an exothermic process okay it is endothermic also in some cases but in general it is exothermic when you dissolve something in water or any solvent there will be some amount of heat releases energy releases okay very simple example you have you have suppose this detergent powder right any detergent powder surfacel anyone you can take take a small amount of it put it on your palm add some water right this four five droplets of water you add okay a little bit of water you add and when you close this you'll see you'll feel some warm inside right when it dissolves you'll feel a bit of heat over there there on your palm right that heat is the heat energy that liberates when the detergent dissolves in dissolves in the water right it's a very simple example of you know exothermic process it is so basically dissolution is in general exothermic process means whenever you dissolve a solid or any substance into any solvent there is a fixed amount of energy releases okay so what is solvation energy first of all we'll discuss the solvation energy is the amount of energy released when one mole of any compound any any solute dissolve in dissolve in a given amount of solvent at a given temperature at a given temperature for a given amount of solvent one mole of solute if you dissolve then the amount of energy that releases is called solvation energy correct one more given amount of solvent and a given temperature because dissolution is temperature dependent also right that's why we define this for a given temperature for a one mole of substance hydration energy is also exactly same and it is a term hydration is the term that we use when the solvent is water that is it okay so for water we have a specific term that is hydration energy right otherwise for any other solvent we call it as solvation energy correct so hydration energy is basically a type of solvation energy right it is another name of solvation energy solvation energy we call it a hydration energy when the solvent is now what happens here the solvation or hydration energy depends upon the degree of hydration right as the size of cation is more degree of hydration is less a smaller amount a smaller size can easily hydrate it okay so hydration energy right down it is the amount of right down it is the amount of energy release it is the amount of energy release when one mole of any substance when one mole of any substance dissolve in water dissolve in water a given temperature dissolve in water at a given temperature right so degree of hydration actually you see degree of hydration means extent basically degree of hydration is inversely proportional to the size of cation bigger the size lesser will be the hydration and hence lesser will be the hydration energy so hydration energy decreases as we go down the group for this cation ni plus we'll have maximum then we have na plus k plus c h plus hydration and the degree of hydration and hydration energy both we can say okay understood okay next slide down next slide down reducing nature see reducing nature is means what that the atom should oxidize and reduce others right so it means oxidize itself and reduce others this is the reducing nature oxidize itself means what it is nothing but the tendency to lose electron right as you lose electron as you lose electron oxidation takes place and it can reduce others right and under what condition it can lose electron when the element has low ionization energy then only it can easily lose electron so basically low ionization energy means low means more reducing nature right so basically if you combine all these things you'll see as we go down the group as we go down the group ie decreases and reducing nature right so if you compare li it has lesser reducing nature than na than k rb this is the order we have in free state free state free state means gaseous state basically no if suppose we have a metal m if it loses electron it converts into m plus plus one electron so this is oxidation so metal itself is going under oxidation and hence it is reducing others just to give me a second right it gains it releases electron and hence it reduces it gets oxidized and reduces others right that's how the thing is understood so when you talk about this reducing nature in gaseous state free state the concept that you are using is ionization energy here but this is not the factor ionization energy is not the factor when we consider this in aqueous state in solution right so right now next thing here in this only write down however the tendency of lose electron in solution however the tendency to lose electron in solution depends upon depends upon many factors like you see we have the solid metal m solid first of all you need to provide the enthalpy of sublimation that is delta h of sublimation so that from solid it converts into gas okay so enthalpy of sublimation is involved now to oxidize this what we need to do you need to provide ionization energy it converts into m plus gas plus one electron so ionization energy also evolve over here right and then when you dissolve this in water h2o it converts into m plus aqueous plus the energy involves here releases that energy we call it as hydration energy so hydration energy is basically depends upon depends upon these three terms enthalpy of sublimation ionization energy and obviously the size of the cation that you are getting right because this energy that comes out it depends upon the size of this cation and we know size of the cation is less extent of hydration is more more energy releases so in case of solution what happens the order of hydration energy right is we know it is maximum for li plus and based on that we write down the reducing nature the li plus will have the maximum reducing nature in solution since it has the maximum hydration energy right so reducing power you write down in solution in solution it is maximum for li than na krb etc right we also say depends upon the standard oxidation potential right so standard oxidation potential is maximum for lithium standard oxidation potential more is more value of standard oxidation potential more is the reducing power in solution right write down more standard oxidation potential more will be the reducing power in solution so in solution it is opposite next write down reactivity towards air write down the next reactivity towards air react towards air when we write this mainly the reaction with oxygen okay write down alkali metals are very reactive alkali metals are very reactive and on exposure to and on exposure to moist air exposure to moist air they forms oxides peroxides and super oxides oxides peroxides and super oxides on exposure to moist air they forms all three types of oxides oxides peroxides and super oxides so basically when we have a metal m with oxygen it forms m2o this is the oxide we have. Further exposure of oxygen it converts into M2O2 which is peroxide. Further it converts into MO2 which is superoxide. Tendency to form oxide it is maximum for like you see here oxide is mainly formed by lithium and to some extent sodium may also form. Lithium mainly forms oxide only and to some extent sodium forms this oxide. If you talk about peroxide it is mainly formed by sodium but to some extent Li also forms this but it is mainly for sodium. Here it is mainly for lithium. So basically you see if you look at the oxides here the statement that I've given you just now this means when you have lithium and lithium when you heat with oxygen O2 atmospheric oxygen around 200 degrees Celsius the temperature is not important it forms oxide of this type Li2O. It won't form the peroxide Li2O2 but if you take sodium here that is Na with O2 and if you heat this even at higher temperature it forms peroxide Na2O2 type oxide. And this superoxide is mainly formed by the other elements like that is potassium, rubidium and cesium and hence we also say that as we go down the group the tendency to form superoxide increases right on that stability of right on first this point that the reactivity of metals towards oxygen reactivity of metals towards oxygen increases as we go from the group reactivity of metals towards oxygen increases as we go down the group okay increases as we go down the group next point next point the stability of the stability of peroxides and super oxides the stability of peroxides and super oxides also increases peroxides and super oxides also increases as we go down the group okay so important property this is one note you write down here on exposure on exposure to towards air on exposure to air you write down lithium also combines with nitrogen lithium also combines with nitrogen and forms nitride and forms nitride right so the reaction only lithium not other metals right only lithium we have here among all the alkali metals lithium on exposure to air it also combines with nitrogen and converts into li3n nitride okay lithium nitride case only lithium can form this see one thing you must remember any group whether it is s-block p-block the first element of every group I'm giving you this general thing right it is valid for all the groups the first element of all the groups will show some will show some abnormal behavior okay like you see lithium is the first element of alkali metals right hydrogen we are not talking about here so it has some abnormal behavior because of its small size less electronegativity and lesser number of electron in the inner shell because of all these things the first element always shows a bit of different behavior right then the other elements of the same group if you have to choose one like suppose one example if I give you you know this fact that the behavior of first element is different from all other right you know this fact now I'm not now you see you got this question like the question is which one of the alkali metals forms nitrides on exposure towards air right you don't have any you don't have any clue like what should be the answer but you know only one point that the behavior of first element is different from the other elements so if the options are given like lithium sodium potassium rubidium right like these four options are given you have to choose one you know the question gives only one correct answer which element show forms nitrides on exposure to air you know the first element has a normal behavior so if you have to choose one if you if you want to have a guess for the question you should go for the first element of that group that is probably most probably gives you the right answer because if potassium shows why not rubidium right why not sodium then because all have the similar kind of behavior but we know the fact that the first elements behaves differently with respect to the other elements so there are high chances that the answer is lithium and you should go for that okay this is true for all the groups even for alkyline earth metal also you'll see the behavior of beryllium is different for boron family boron behavior is different carbon behavior is different okay is that's why ncrt you see they'll give you abnormal behavior of lithium if when you open up the book you'll see it is written the topic over there abnormal behavior of lithium abnormal behavior of boron beryllium and so on right this is because of their small size and lesser number of electrons in there in a shell okay so this point is general thing you must keep in mind okay so this is one thing now one note you write down here because of high reactivity towards air because of high reactivity towards air alkali metals are kept in kerosene are kept in kerosene because it is non reactive in kerosene this also they ask why alkali metals are kept in kerosene what is the reason for this then next write down reactivity reactivity towards water the reaction is 2m plus h2o it forms hydroxide and hydrogen gas evolves into this so alkali metals reacts with water forms hydroxide and evolves hydrogen gas write down the reactivity of alkali metals of alkali metals with water increases increases down the group so reactivity is more the reason is the more rate of reaction okay the rate of reaction also increases and hence the reactivity with water also increases over here then next write down reactivity towards hydrogen what kind of hydride it forms we have discussed last class tell me what kind of hydride it forms yes could you check your notes yeah last class only i had discussed okay ionic hydride it forms okay so write down alkali metals reacts with hydrogen reacts with hydrogen and forms and forms ionic hydride of mh type ionic hydrides of mh type okay from ionic hydrides of mh type now the properties of these hydrides are important okay so write down into this the first point mh type you have written these hydrides have nacl type structure i'll discuss what is this first few points write down i said alkali metals reacts with hydrogen and forms hydrides of mh type mh type means like this i meant this if you have a reaction 2m plus h2 on heating it gives 2m h means molecular formula is this mh type m is any metal slightly ethium sodium potassium anything that is mh type first property in write down it has nacl type structure it has nacl type structure the ionic character of these hydrides increases down the group means if you compare li h na h k h the ionic character increases and covalent character decreases anybody explain here why ionic character increases could you explain the reason here why ionic character increases yes correct no no no no already pradyum that's right see what happens i have discussed one concept of fazan's rule if you remember and there we'll talk about there we'll talk about the polarization it deals with the ionic character right the covalent character in ionic compound okay and there one factor we had discussed that as the size of cation increases polarization decreases and covalent character decreases so as you go down the group you see li plus na plus k plus the size of cation is is increasing and hence covalent character decreases ionic character increases correct next write down the stability of hydrides decreases down the group right so from top to bottom if you go top to bottom if you go the stability decreases why stability decreases again size increases bond length increases stability decreases and since stability decreases we can also say reactivity increases all these things are related reactivity increases down the group no doubt no in general we say in general we say reactivity increases for any reactions we can say okay yeah tell me okay these properties of hydrides you must keep in mind they can ask you any one of these okay relation i have already told you how to relate all these things you can understand easily next write down reactivity towards halogen reactivity towards halogen i forgot to discuss one thing na cl type structure means what this in detail you will study in solid state in na cl what happens na and cl minus are present like this in cubic crystal system they arranged i don't draw this okay just you see this in this what happens the na plus present here at the edge center all edge center na plus is present there's a cube of equal like we have cubes and these edge center we have na plus present plus at the body center also na plus present right so all the red dots you see are na plus and cl minus are present at the corners these corners there are eight corners so we have eight cl minus like it is present at the face center all the face center all the face center like this so black dot that you see it is the position of cl minus and red dot is the position of na plus okay this we call it as na cl type structure this we also called rock salt type structure or rock salt structure okay so 12th class you will have solid state there we'll discuss all these things in detail but lithium hydride also it is it has same or the hydrides of alkali metals have similar kind of structure understood next write down reactivity towards halogen write down alkali metals reacts vigorously alkali metals reacts vigorously with halogens and forms and forms halides of and forms halides of mx type like na cl kcl all these types okay halides of mx type reactivity towards halogen if you see it increases down the group because again ionization energy decreases so for alkali metals the reactivity order is this if you talk about the halogens halogens the reactivity of fluorine is maximum towards any one of the alkali metals okay this is again f2 cl2 br2 i2 okay I said the first line under this topic that alkali metals reacts with halogen vigorously vi go ro us ly vigorously and forms halides of mx type forms halides of mx type for metal if you look at the reactivity of metal towards any halogen down the group the reactivity increases if you look at this for any halogens for halogen towards any metal the reactivity down the group for halogen decreases it is maximum for fluorine and minimum for iodine why it happens easily you can understand you see the bond na cl if you see I have discussed this many times na cl molecule how it forms first of all it is an ionic compound na plus and cl minus so how na plus forms when sodium releases one electron it forms this right how cl minus forms chlorine takes one electron and forms this okay so here we need to talk about the ionization energy plus enthalpy of sublimation also because solid you need to convert first into gas and then ionization energy here also we have electron affinity right we need to consider here basically halogens are accepting electron and alkali metals are losing electron so electron losing tendency increases down the group hence reactivity is this electron accepting tendency is maximum for fluorine high electronegativity hence reactivity orders so overall we have these two order clear can you doubt in this next write down reactivity towards liquid ammonia liquid ammonia write down alkali metals are highly soluble in ammonia highly soluble ammonia write down this solution shows deep blue color this solution shows deep blue color which has the following properties following properties first one the solution is the first one write down like this solution is paramagnetic good conductor of electricity electricity strong reducing agent reducing agent and irrespective irrespective of metal the color of the solution is blue the solution is blue the reaction is you see here metal we have solid plus n h 3 it gives m n h 3 x positive charge plus electron m h 3 y negative charge this is the reaction we have this electron is actually surrounded by the ammonia right so this electron we call it as ammoniated electron ammoniated electron and this is responsible for the color of the solution for color and hence whatever metal we use irrespective of the metal electron is electron only right so whatever metal we have the color of the solution is blue only ammoniated electron is this we have electron and this electron it's surrounded by ammonia molecule in which hydrogen is towards this electron all these have delta plus delta negative and delta positive delta positive delta positive this electron is ammoniated electron because of this only it is conductive the solution is conductive in nature and shows blue color understood this electron right down here it is ammoniated electron responsible for the conductive behavior and blue color of the solution important this one is okay must remember this okay so this is it for ammonia solution we'll take a break now and after the break we'll see carbides okay this will start with after the break carbides and then carbonates bicarbonates we'll discuss after this fine take a break now we'll resume at 6 30 take a break guys any doubt you have in this yes fine guys take a break 6 30