HYDROGEN Notes

HYDROGEN
Hydrogen is the first element in the periodic table. Its atomic number is one. Its electronic configuration is 1s¹.

· Isotopes of Hydrogens

   The atoms of an element having the same atomic number but different atomic mass are called isotopes.

Isotopes of Hydrogen

1) Protium ( Ordinary Hydrogen

Symbol – ¹₁H

Atomic number – 1

No of neutron – 0

Atomic mass(stp) – 1

Abundance – 99.9%

Application

-   Used in filling ballons

-   Used in Habber’s process

-   Used as reducing agent

2) Deuterium ( Heavy Isotopes )

Symbol – ²₁H

Atomic number – 1

    No of neutron – 1

Atomic mass(stp) – 2

Abundance –  0.1%

Applications

-  Used in preparing heavy water (D₂O )

-  Used in tracer technique to study complex mechanisms

 

3) Tritium ( Radioactive isotope )

Symbol – ³₁H

Atomic number – 1
  No of neutron –2

Atomic mass(stp) – 3

Abundance – Trace

Application

-   Used in tracer technique to study complex mechanism

-   It is the good source of radiation

-   Used to carry out nucleus fussion reaction

 Types of Hydrogen

1) Molecular Hydrogen (H₂)

Uses

- Used in the hydrogenation of vegetable oils

- Used as reducing agent in laboratory and industry

  - Used in the manufacture of synthetic petrol

 

2) Nascent Hydrogen ( H )

The newly born Hydrogen or the hydrogen at the moment of origin is called nascent Hydrogen.

Zn   +    dil.   H₂SO₄   =      ZnSO₄    +   2[H]

Zn    +   HCl     =     ZnCl₂     +  2[  dil.  2H]

It is very highly reactive and should be prepared in the presence of oxidizing agent. It is more powerful reducing agent then molecular Hydrogen because it can reduce acidified KMnO₄, K₂Cr₂O₇ and FeCl₃ but with molecular Hydrogen no reaction talks place.

FeCl₃         +     H     =   FeCl₂     +    HCl

Reddish yellow               light green

 

3) Atomic Hydrogen [H]

The Hydrogen produced by the dissociation of molecular hydrogen gas by passing gas by passing electricity is called atomic Hydrogen. The reaction is endothermic. The atomic Hydrogen thus produced is very highly reactive and combines with each other to form molecular Hydrogen gas again. It can have life period of about 0.3sec. It is more powerful then rest Hydrogen.

  

Allotropes of Hydrogen

1) Ortho Hydrogen

The dihydrogen molecule in which the nuclear spin of two Hydrogen atoms is in same or parallel direction is called Ortho Hydrogen. It is more stable at ordinary or high temperatures and found to 75%.

Parahydrogen           =         Orthohydrogen

                       ( 800⁰C,Heat)

 

2) Para Hydrogen

The dihydrogen molecule in which the nucleus spin of two Hydrogen atom is in opposite direction is called parahydrogen. It is more stable at low temperature and found to be about 99% at absolute zero.

Orthohydrogen       =         Parahydrogen

                       ( 20K,Ni )