On the earth Hydrogen exists as H2 molecule (dihydrogen). It constitutes to 10 % mass of universe. Hydrogen exit in many substances like carbohydrates, hydrocarbons etc. It is actually 3rd most abundant element
Characteristics of Hydrogen
Similarities with alkali metals – Its similarities with alkali metals are given below
Same number of valence electrons -1
Like alkali metals it has electropositive character
Oxidation state =+1, example is in HCl
It is strong reducing agent.
For Example: – Fe2O3 + 3H2 à 2Fe + 3H2O
Ferric Oxide Hydrogen Iron Water
Difference with alkali metals –
|Ionisation energy of Hydrogen is high as compared to alkali metals||Ionisation Energy of alkali is less.|
|Shows non -metallic behaviour||metallic behaviour|
|Diatomic molecule as gas||monoatomic|
|Hydrogen mostly form covalent bonds||Ionic bonds|
Similarities with Halogens –
- Hydrogen has only Ionisation energy less than noble gases.
- Ionisation energies of Hydrogen is 1312 kJmol-1 close to chlorine.
- Oxidation state of Hydrogen is -1 in many compounds.
- H2 is diatomic.
- Hydrogen is non-metallic and exists in gaseous state.
Differences with Halogen –
|Hydrogen has fewer tendencies to accept electron.||They have more tendencies to accept electron.|
|It has no unshared electron pairs.||They have unshared electron|
|Their oxide is neutral||Their oxide is acidic|
- H2 Preparation (in laboratory)—
It is formed in labs by reacting granulated Zinc with dilute hydrochloric acid . The apparatus used is shown in figure:
Out of all methods : Different methods are used to yield hydrogen as shown :
By Pertoluem Method 77%
By Electrolysis Method 18%
By other sources 1%