Hydrogen and its compound .class 11th and iit-jee

HYDROGEN AND ITS COMPOUND.Class 11th and IIT- JEE.

 In chemistry we are starting HYDROGEN ANDITS COMPOUNDS.        

 In the topic HYDROGEN AND ITS COMPOUNDS,The very first thing is, How was hydrogen discovered?

What is its position in periodic table? 

And on what basis hydrogen is said to be anelement for which a fixed position has not been assigned in periodic table.

 Then after we shall study about the methodsto prepare diatomic hydrogen, Its properties and then the compounds of thehydrogen, So the things start from its discovery,Hydrogen for the first time was obtained by the action of certain metals on some acids,By the reaction between some active metals and some acids,Hydrogen gas was liberated.

 The name hydrogen was given on the basis onthe fact that hydro word stands for water. And gen means, the derivative. So on burning, on combustion hydrogen formsH2O, On that basis it is considered to be waterproducing gas. 

So hydrogen was discovered this way and the name hydrogen was given on this basis. After its discovery hydrogen was found tobe prepared by some chemical methods, There are some laboratory and other methodsof its preparation. And in continuation we will talk about itsproperties also.

 But before coming to all these points,Let us talk about the element hydrogen with its position and the other things. Hydrogen has atomic number 1 and it existsin 3 different isotopic forms, It is protium, deuteriumDeuterium is actually the isotope of hydrogen with mass two and it is denoted as either1H2 or simply D, Tritium is another isotope.

,Actually it is a radioactive isotope of hydrogen, Its mass number is three; it is also denotedas T. So these are the three isotopes of hydrogen. Among the three isotopes protium isotopesis most abandoned, And due to that reason the average atomicmass come to be nearly 1 only. Protium is more abandoned as compare to deuteriumand tritium, And therefore for all the particle purposesthe average atomic mass.

Since it comes nearly equal to 1So for all the particle purposes, For all the chemical calculations,The atomic mass of hydrogen is taken as 1.

 Now about its position in periodic table,As we know its electronic configuration is 1S1,Looking at the configuration. It resembles alkaline metals,So regarding the position of hydrogen Since it has been found to contain the valenceelectron as orbital, It has been placed in first group of periodictable, In hydrogen there are certain properties similarto the alkaline metals, But at the same time there are certain propertiessimilar to the halogens also.

That is why the position of hydrogen has adispute, The position of hydrogen in periodic tableis a disputed proposition, Some scientist say that,Hydrogen has a resemblance with alkaline metals.

 Which is a fact. But at the same time another fact is its resemblancewith the halogens. This way due to its resemblance with two extremegroups, The group of alkaline metals and the groupof halogens, The position has not been expressed clearlyin the initial classifications. 

Although in the modern periodic table, theposition of hydrogen has been given in the first group of periodic table. Hydrogen has been placed in the first groupon the basis of its configuration. 

Let us talk now about the properties in which hydrogen has similarity with alkaline metals. Similarity with alkaline metals,The presence of one electron in valence shell, That means similar electronic configuration. 

This is the first thing in which hydrogenresembles the alkaline metals. Shows plus 1 oxilation state in compounds,The oxidation state of alkaline metals in their compound is +1,That of hydrogen in compounds is also +1. It forms compounds with nonmetals. 

Forms compound with halogens specifically. Although halogens are the nonmetals but Ihave mentioned it as a separate point, Because halogens they form compounds withalkaline metals in which halogens are present in the form of negative irons. 

Although with hydrogen the compounds of halogenswith hydrogen, They are covalent compounds but still theoxidation state of hydrogen is plus 1, And halogens have minus 1 oxidation number,This way these are some key points where alkaline metals and hydrogen have a resemblance.

 We can also mention the property of reducingcharacteristics. Alkaline metals have a strong reducing nature,Similar is hydrogen it has a reducing nature So these are dome of the points where hydrogenresembles the alkaline metals. 

But at the same time,We have similar points where hydrogen has resemblance with halogens. Similarity with halogens,These were the points of similarity of hydrogen with alkaline metals and now similarity withthe halogens. 

What do we think? Where hydrogen should resemble halogens? If one electron is accepted by gained by hydrogen,It acquires the configuration of noble gas. Halogens have the similar thing,If they gain one electron, the stable inert gas configuration is acquired. So similarity with halogens gaining of an electron gives stable electronic configuration.

 Ionization energy of hydrogen is comparable to halogens. Halogens and hydrogen have comparable valueof ionization energy. Forms compound in minus 1 oxidation state. Hydrogen forms compound in minus1 oxidationstate with metals. Similar is the property of halogens they alsocombine with the metallic element and exist in the form of negative irons.

 So forms compound in minus one oxidation statewith metals. With the metals the compound formed by hydrogenis called as hydride and the compounds formed by halogens are called as halides. 

So hydrides and halides they have negativeoxidation in number of this elements. These are certain points of resemblance wherehalogens and hydrogen have a similar thing. 

Both are non metallic elements. Hydrogen is a non metal, halogens are nonmetals. And in fact their elemental existence is similar. Elemental existence means both exist if thediatomic molecular form. 

So non metallic nature and existence in theform of diatomic molecule, These are the points where hydrogen has aresemblance with halogens. 

If we see these properties of hydrogen thenthese properties of hydrogen show a difference of hydrogen from alkaline metals in the properties.

 And if we these properties of hydrogen,Then these properties are the dissimilarities of hydrogen from halogens.

Means similarity of hydrogen with alkalinemetals show dissimilarity of hydrogen from halogens,And similarities of halogens with halogen show the dissimilarity of hydrogen with alkalinemetals.

 This way the position of hydrogen could notbe assigned properly in the initial classification. Later on it has been accepted that modern periodic table has all elements placed on the basis of their electronic configuration. 

And that is why hydrogen has been placed infirst group of periodic table. So now this was about an introduction aboutthe element. Hydrogen! As I have said it was discovered initiallyby the chemical reaction in which metal acted upon the acids.

 The name hydrogen was derived on the basisof its water forming property. Hydro- water, gen- producing. So that way hydrogen is found to be the 9thmost abundant elements in earth's crust. 9th most abundant. Hydrogen is found to combine with many ofthe metallic elements. 

The compounds form by hydrogen with metalsis usually ironic. And hydrogen exists in the form of negativeiron. The compounds forms by hydrogen with nonmetalsare called as are having the nature covalent. 

So compounds of hydrogen with metals are ionicthey are called as hydrides. Because hydrogen is in the negative oxidationstate, And the compounds of hydrogen with the nonmetalsare covalent in nature, Where the oxidation state of hydrogen is positive,After all these things we should come to the preparation of the diatomic hydrogen.

 How can we prepare the diatomic molecularhydrogen, See the chemical reactions. Preparation! We are talking about preparation of the diatomicmolecular hydrogen. 

One of the methods of preparation of hydrogenis from water. From water hydrogen can be prepared. By the reaction with active metals like sodium,potassium, Equation shown are not balanced calciumIn all such reactions metals hydro oxides are formed and hydrogen gas is liberated.

 So these are the reactions where from waterwe get hydrogen, by reaction with metals. Another way to produce hydrogen from wateris by its electrolysis.

 So by the electrolysis process,Pure water cannot be electrolyzed. Since pure water cannot be electrolyzed becauseit is not conducting.

 If we add a small amount of acid or a baseor salt in water, Then it is possible to electrolyze water. The electrolysis of water gives hydrogen andoxygen gases at cathode and at anode respectively. 

Hydrogen obtained cathode is due to the reductionof H+ irons. Oxygen obtained at anode is due to the oxidationof hydroxide irons. H+NOH- These irons are only produced when small amountof acid, base or salt is present in water. Because then only it becomes conducting,Otherwise water is not conducting. So by the electrolysis of water, hydrogenand oxygen gasses are obtained and this makes one of the methods of preparation of the atomichydrogen.

 Another method is from metal hydrides,Metal hydrides! There are certain metal hydrides,One of the most common metal hydride is calcium hydride. CAH2 With water it liberates hydrogen,So metal hydrides are hydrolyzed reaction with water is called as hydrolysis. 

So metal hydrides give hydrogen gas by thistype of reaction, Other metal hydrides can also be taken. Like lithium hydride, lithium hydride formslithium hydroxide and liberate hydrogen.

 Another form, another way to produce hydrogengas is from acids. Acids react with active metals by reactionwith active metals. 

Active metals means metals which are placedabove hydrogen in electro chemical series. That means in the reactivity series the metalsabove hydrogen's they liberate hydrogen when reacted with acids. For example zinc on reaction with HCL liberateshydrogen. Again zinc on reaction with dilute sulphuricacid liberates hydrogen. 

This particular method is used for the preparationof hydrogen in laboratory. So this is the laboratory method of preparationof hydrogen.

 

Remember we take dilute sulphuric acid andit is allowed to react with zinc. In the reaction it is compulsory to take dilutesulphuric acid because concentrated sulphuric acid does not produce hydrogen gas.

 Rather it produces sulphur dioxide gas, dueto the reaction between hydrogen and sulphuric acid. So the liberated hydrogen because of oxidizingproperty of concentrated sulphuric acid it forms water,Rather then hydrogen it undergoes oxidation to form H2O and sulphuric acid itself reducedinto sulphur dioxide. These are certain methods from acids. 

It's not that you can take only zinc,Magnesium, iron etc type of metals can be taken. For example if you take iron with HCL theproduct is ferrous chloride and hydrogen. 

So these are the reactions of acids with activemetals to produce hydrogen, We have another methods where hydrogen gas can be liberated from the bases like NAOH, KOH etc.