• Resemblance with alkali metals.
• Resemblance with halogen.
• Difference from alkali metals & halogen.
• Preparation of hydrogen.
2. • Properties of Dihydrogen.
• Uses of dihydroen.
• Hard water soft water.
• Removal of hardness.
4. •Hydrogen : It is the first element in the periodic
table with the atomic number 1. The Hydrogen
Ion ( H+ ) never exist in free state, it is always
found in combined form.
•It resembles the first group elements and halogen
group due to its anomalous character .
5. Electronic Configuration : contains one
Electron In the outermost shell.
Electropositive : Like Alkali metals, Hydrogen
also looses its one electron to form hydrogen
ion, i.e., H+ .
Resemblance With Alkali
6. Combination With Electronegative Elements :
Like Alkali metals Hydrogen also combines
with electronegative elements such as oxygen,
Oxidation State : Like Alkali metals Hydrogen
also shows the oxidation state of +1 I its
7. Reducing Character : Like Alkali metals
Hydrogen also act as a strong reducing agent.
8. Electronic Configuration : All the Halogen
wants one electron to complete its octet, this
property is shown by Hydrogen also.
Electronegative Character : Halogens have a
strong tendency to gain electron to form halide,
Hydrogen also shows same tendency.
Resemblance With Halogen
9. Ionization Enthalpy : Ionization Enthalpy of
Hydrogen is quite comparable with those of the
Oxidation State : Just Like halogen Hydrogen
shows the oxidation state of -1.
Combination With Metals : Hydrogen combines
with the metals in the same way as the halogens
10. • Nature Of oxides : Hydrogen forms oxides that
are neutral unlike alkali metals & halogen.
• Size Of ions : The Size Of ions Are Not
Comparable with the size of the ions of alkali
metals & halogen.
Difference From Alkali Metals
• 1 H → Protium : The only isotope without
• 2 H → Deutrium : The isotope that is used as
nuclear moderator in nuclear reaction .
•3 H → Tritium : The only isotope of Hydrogen
that is radioactive .
12. Lab Preparation :
• Reaction Of dilute acid or bases with
• Zn + HCl ZnCl2 + H2
• Zn + 2NaOH Na2ZnO2 + H2
Preparation Of Hydrogen
13. • Reaction with Water on Sodium Hydroxide.
• By reaction of KOH on scrap Aluminium.
( Uyeno’s Method )
15. • Reaction Of steam with Hydrocarbons in the
presence of Catalysts.
CH4 + H2O CO + H2
• (Co + H2 ) → Water Gas or Syngas or
• (CO + N2) → Producer Gas
16. • Coal Gasification Reaction
• C(s) + H2O (g) CO + H2
• Water Gas Shift Reaction :
• CO + H2O C O2 + H2
• General Form:
• Cn H2n+2 + n H2O nCO + (2n+1) H2
• Colourless, Tasteless & odourless.
• Lightest substance.
• Slightly soluble in water.
• Can be liquefied under low temperature & high
Properties Of Dihydrogen
• Neutral Character.
19. • Reaction With Metal:
2Na + H2 2NaH
• Reaction With Dioxygen:
2 H2 + O2 2 H2O
20. • Reaction With Halogen :
H2 + X2 2HX (X=F, Cl, Br, I)
• Reaction With Dinitrogen :
N2 + 3H2 2NH3
• Reaction With Sulphur :
H2 + S H2S
21. • Reaction With Carbon :
C + 2H2 CH4
• Reduction Of Metal Oxides & Ions :
• General form :
MxOy + yH2 x M + yH2O
22. • Hydrogenation Of Unsaturated Hydrocarbons :
Unsaturated hydrocarbons such as alkenes &
alkynes add Dihydrogen in presence of catalysts
to form saturated hydrocarbons.
RCH=CH2 + H2 + CO RCH2CH2CHO
RCH2CH2CHO + H2 RCH2CH2C H2OH
23. • Hydrogenation of Vegetable Oil to solid fats.
• Manufacturing of bulk chemicals such as
• Manufacture of Ammonia ( Haber’s process ) .
Used Of Dihydrogen
24. • Manufacture Of metal Hydrides .
• In Metallurgy to reduce heavy metals.
• Used as liquid hydrogen.
25. • The various elements that form hydrides are
i. All the main group elements except those of
noble gases & probably indium & Thallium.
ii. All Lanthanides & Actinides.
iii. Transition elements .
• On the basis of physical 7 chemical properties
hydrides are categorized in three groups.
26. Ionic or salt like or Saline Hydrides :
• These are formed by transfer of electrons from
the metals to the hydrogen atoms & thus
contain hydride ion.
• The density of these hydrides is higher than
those of the metals from which they are formed.
This is because Hydrogen ion occupies holes in
the lattice of the metal without disturbing the
27. • These are white crystalline solids 7 their crystal
structure consists of ions.
• They have high melting & boiling points and
conduct electricity in fused state, liberating
• They react violently with the water to form
their respective metal hydroxides, with the
liberation of Dihydrogen. The act as strong
28. • They are very powerful reducing agents,
especially at high temperature.
• They have high heat of formations 7 are always
• Examples are NaH, CaH2 etc.
29. Metallic or Interstitial Hydrides :
• These are formed by the transition elements.
• They are hard, have a metallic luster, conduct
electricity and have magnetic properties.
• The densities of these hydrides is lower than
those metals of which they are formed since the
crystal lattice expands due to inclusion of H2.
30. • The metals of group 7,8 and 9 do not form
hydrides. Infact this region from group 7—9 is
called as hydride gap.
• These hydrides are often non-stoichiometric .
• Example : La H2.87 , Ti H1.5-1.8 .
31. Molecular or Covalent Hydrides .
• When transition elements from hydride, they are
called metallic or non-stoichiometric.
• On the basis of electron number the metallic
hydride is classified is divided in three group.
32. i. Electron Deficient :
BH3 13th group.
ii. Electron Precise :
CH4 14th group.
iii. Electron Rich :
H2O, NH3 15th, 16th, 17th group.
34. Physical Properties :
• The freezing point , BP, heat of fusion, heat of
vaporization, of water are very high because of the
presence of intermolecular hydrogen bonding.
• Water has high specific heat, thermal conductivity,
surface tension, high dielectric constant.
35. • Chemical properties :
• Amphoteric nature :
H2O + N H3 O H- + N + H4
(Acid) (Base) CB CA
H2O + H2S H3O+ + HS–
(Base) (Acid) CA CB
36. • Autoprotolysis : One molecule act as a base and
another molecule acts as acid.
• Redox reactions involving H2O
H2O + Na NaOH + H2 .
( Reduction of H2O )
CO2 + H2O C6H12O6 + H2O + O2 .
( Reduction of H2O )
37. • Hardness of water depends upon hydrogen
carbonate, chlorine, sulphate and salts of Ca &
• Temporary hardness is due to HCO3 Of Ca &
• Permanent Hardness is due to Cl and SO4 of Ca
Hard Water & Soft Water
38. Removal Of Hardness
39. • Removal of temporary hardness:
Mg(HCO3)2 Mg(OH) 2 + CO2
Ca(HCO3)2 CaCO3 + H2O + CO2
Removal Of Hardness