Hydrogen Class 11 Notes Chemistry Chapter 9 || Why position of hydrogen is not fixed in elements periodic table || What is the Occurence of hydrogen element || What are the Isotopes of hydrogen || What is water gas shift reaction

Hydrogen Class 11 Notes Chemistry Chapter 9

Hydrogen class 11 notes chemistry chapter 9. Why the position of hydrogen is not fixed in elements periodic table. What is the Occurrence of hydrogen element. What are the Isotopes of hydrogen. What is water shifted reaction.

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Hydrogen Class 11 Notes Chemistry Chapter 9

Why the position of hydrogen is not fixed in the elements periodic table?

Periodic position of hydrogen

According to the electronic configuration

H: 1s¹ 




But Periodic table based on the property of the element and property of hydrogen match with group 1st (alkali metal) as well as group 17 (halogen group).

 So, hydrogen is not placing group 1st as well as group 17. It is a study separately as a little hydrogen and its compound.

Classification of element(Hydrogen) based on property

1) Group-1(Alkali metal)(s-Block)

2) Group-17 (Halogen)(p-Block)

Property of hydrogen match with group 1st

           Hydrogen                    Group-1 Alkali metal


i) Outermost E.C.=1s¹              i)  ns¹(n=2,3,4,5,6,7)

ii) H - 1electron=H+                 ii) Na - 1=Na+

iii) H2 + O2= H2O                     iii) Na + O2= Na2O

iv) H2 + Cl2= 2HCl                    iv) Na+Cl2=NaCl

Property of hydrogen match with group 17 (halogen group)

Hydrogen. Halogen group
(F, Cl, Br, I)
1. It exists in diatomic form (H2) 1. It exists diatomic form(F2, Cl2, Br2, I2)
2. H gain one electron and convert into H- 2. It gains one electron and converts: F-, Cl-, Br-, I-
3. High ionization potential 3. High ionization potential
4. React with metal
Nah, CaH2, AlH3
4. React with metal
NaCl, CaCl2, AlCl3

What is the Occurrence of hydrogen elements?

It is the most abundant element in the universe. The composition is as follows:-
•Universe contain 70% hydrogen.
• Earth's atmosphere contains very less amount hydrogen (0.15%) due to being lighter.
•Earth crust contains 15.4% hydrogen.
•Hydrosphere H2O contain 11.1% hydrogen.



% of H2=2×100/18=11.1%

•Plant and animal also contains hydrogen in the form of carbohydrates and protein.

What are the Isotopes of hydrogen?

Hydrogen has three isotopes. It is separated by Urey(a name of a scientist). This isotope is Protium, Deutrium, Tritium.

Method of preparation of hydrogen (H2)

1. Lab method

Metal + acid= Salt + H2

Metal + base= Salt + H2

Zn + H2SO4(Dil.) = ZnSO4 + H2

Zn + NaOH = Na2ZnO2 + H2

2. Commercial method

Chlor Alkali process

When brine solution is electrolyzed then hydrogen gas is formed. Besides hydrogen gas, it also gives Chlorine (chlor) and Alkali (NaOH). So it is called the  Chlor Alkali process.

NaCl + H2O =(electrolised)= NaOH Cl2 + H2

NaCl + H2O= Brine

NaOH= Alkali

3. Lane process

Fe + H2O(steam) = Fe3O4 + H2

Fe3O4=mixed oxide of FeO and Fe2O4

FeO= Ferrous oxide

Fe2O3= Ferric oxide

So, Fe3O4 is known as Fersoferric oxide.

Hydrogen from saturated hydrocarbon

When saturated hydrocarbon(alkane) react with steam then it gives a mixture of CO and H2. This mixture of gas (CO + H2) is called water gas. This gas is used to synthesise many organic compounds. So it is also called synthesis gas or syngas gas.

CnH2n+2 + nH2O(steam)→nCO+(2n+1)H2 

C4H10 + 4H2O → 4CO + 9H2 

CO + H2: Water gas 

After liquification:- CO(liquid) + H2(liquid)

After distillation:- CO and H2: separated

Further CO react with H2O(steam)

CO + H2O→CO2 + H2

This reaction is known as water shifted reaction.

What is a water gas shift reaction?

Water-gas which is obtained from liquefication and distillation then, both separated be obtained H2 and CO separately. Further, CO reacts with H2O (steam) and gives hydrogen and carbon dioxide gas this reaction is called the Water gas shift reaction.

To be continued.......

Read more topics in the next article such as



Metallic or Non-stoichiometric


To be continued.......

Next part here 👉Hydride of hydrogen electron 👈

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