What is Hydrogen and its atomic mass? | properties of hydrogen

What is Hydrogen? Hydrogen is the lightest and simplest element with no smell, taste and color. Its atomic number 1, symbol (H), molecule (H2) and atomic mass are 1.008 g mol−1. It occupies the first position in the periodic table.

Its atom consists of only one proton and one electron. Because it is an active element, it is not found independently on Earth but is found in compounds with many other elements. This gas is found on earth as a compound in water, acids, carbohydrates, oil, diesel, petrol, etc.

What is hydrogen

Unsaturated hydrogen is found in a small amount of air. Its volume in the upper air is more than expected. This gas is abundant in the stars and it plays a major role in the process of generating heat and light.

The density of ‘H’ is 0.09 grams per liter. It becomes liquid and solid at very low temperatures. Liquid hydrogen boils at -253 ° C and solid hydrogen melts at -258 ° C.

See also: What is oxygen?

What is a hydrogen bond?

A Hydrogen bond is a bridge between two electronegative atoms which acts as a bridge. It is also called -H- bond. The energy of the hydrogen bond (about 5 to 30 kJ / mol) is comparable to a (Week) covalent bond (155 kg/mol). A special connective bond is about 20 times stronger than an intermittent hydrogen bond.


Henry Cavendish was the first to recognize hydrogen gas as a discrete substance. He speculated that "flammable air" was in fact similar to an imaginary substance called "phlogiston" and further found in 1781 that gas produces water when it burns.

He is generally credited with the discovery of hydrogen as an element. They obtained it by the reaction of dilute sulfuric acid on iron and were called flammable air. In 1883 Lavoisier named it hydrogen because it burns with oxygen to form water. The name hydrogen is taken from the Greek word ὑδρο γενής. (ὑδρο - hydro meaning "water" and γενής - genes meaning "creator")

How to make hydrogen in the laboratory

In the laboratory, hydrogen gas can be made by chemically reacting certain metals such as zinc, magnesium, iron, etc. with dilute hydrochloric acid or dilute sulfuric acid.

Zn (s) + 2HCl(dil) (aq) ® ZnCl2(aq) + H2(g)

Mg(s) + 2HCl(dil)(aq) ® MgCl2(aq) + H2(g) 

Things to pay attention to when making ‘H2’ gas in the laboratory.

  • Pure zinc should not be used as it reacts slowly with dilute sulfuric acid.
  • Hard sulfuric acid should not be used as it gives off other gases (sulfur dioxide) instead of H2 gas.
  • Ulf bottle should be made airtight with cork.
  • Once sulfuric acid has been added to the experiment material, the flame should not be moved near it.

Industrial production of hydrogen

Hydrogen atom released by a chemical reaction that is more active than molecule hydrogen. This is called nascent hydrogen but soon two hydrogen active atoms combine to form a hydrogen molecule.

H2 gas in industries is produced by the following two processes.

From hydrocarbons and water vapor

To produce large amounts of hydrogen, methane is reacted with boiling water vapor at high temperatures (1200 C). Powdered nickel is used as a catalyst in this reaction.

                                             9000 -12000C

CH4 (g) + H2O (steam)           ®                     CO (g) +  3H2(g)


From the electrolysis of water

Hydrogen gas is also produced in industries by electrolysis of water.

Properties of hydrogen

Physical properties

  • This gas is odorless, odorless, and tasteless.
  • It is the simplest gas and is lighter than air.
  • This gas is extremely soluble in water.
  • Hydrogen can also be made liquid and solid at high pressure and low temperature.
  • Its boiling temperature is -253 ° C and melting temperature is -258 ° C. 
  • Hydrogen does not react with litmus paper.

Chemical properties

1. This gas burns in air or oxygen and becomes water.

     2H2(g)  + O2 ® 2H2O(l)

2. It combines with metals such as sodium, potassium, and calcium to form hydrides.


2Na + H2 ® 2NaH


Ca + H2 ® CaH2

3. Forms metal and water by reacting with some metal oxides.

Fe3O4(s) + 4H2 ® 2Fe(s) + 4H2O(l)

ZnO(s) + H2 ® Zn(s) + H2O(l)

CuO(s) + H2 ® Cu(s) + H2O(l)

PbO(s) + H2 ® Pb(s) + H2O(l)

4. It reacts with some halogens to form halides.

H2 + F2 ®  2HF

H2 + Cl2 ®  2HCl

H2+ Br2 ®  2HBr

H2 + I2 ®  2HI

5. Hydrogen reacts with nitrogen at about 200-600 atmospheric pressure and 5000C to form ammonia gas.


3H2 + N2                    ®                     2NH3

                              5000C + Ni

Use of hydrogen gas

  • It is mixed with helium and used to fill balloons.
  • This gas is used to make vegetable oil.
  • Hydrogen gas is used to make chemical fertilizers. It is used to make fertilizers like ammonium sulfate, ammonium phosphate, and urea.
  • When it is burned with oxygen, high heat is released, which is called hydrogen flame. It is used in smelting, cutting, and welding of metals.
  • It is used as fuel in rockets.

Conclusion: Hydrogen is the most important and useful element which plays a major role in the process of generating heat and light.

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