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D - And F - Block Elements

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d and f Block Elements PDF Notes, Important Questions and Formulas

d-Block Elements

Definition: They are often called "transition elements" because their position in the periodic table is between s-block and p-block elements

Typically, the transition elements have an incompletely filled d-level. Since Zn group has d10 configuration and are not considered as transition elements but they are d-block elements.

General characteristics:

  1. Metallic character: They are all metal and good conductor of heat & electricity
  2. Electronic configuration: (n-1)d1-10ns1-2

    begin mathsize 12px style table attributes columnalign left end attributes row cell text                                           end text table row cell space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space Sc end cell Ti straight V Cr Mn Fe Co Ni Cu Zn end table end cell row cell other text    end text are text     end text as text    end text usual open curly brackets table row blank blank blank blank cell 4 straight s to the power of 1 end cell blank blank blank cell space             4 straight s to the power of 1 end cell blank row blank blank blank blank cell 3 straight d to the power of 5 end cell blank blank blank cell space                           3 straight d to the power of 10 end cell blank end table close end cell end table end style
  3.  M.P

    begin mathsize 12px style table row Cr row Mo row straight W end table open table attributes columnalign right end attributes row blank row blank end table close curly brackets table row cell rightwards arrow with blank on top straight thin space maximum end cell row cell 6    no. straight thin space of space unpaired space straight e to the power of minus space straight s end cell row cell are space involved space inmetallic space bonding end cell end table               table row Zn row Cd row Hg end table open table attributes columnalign right end attributes row blank row blank end table close curly brackets table row cell rightwards arrow with blank on top lowest straight space straight m.. straight space straight p. end cell row cell due space to space no space unpaired space straight e to the power of minus end cell row cell for straight space metallic space bonding end cell end table end style
  4. Variation in atomic radius:


    decreases remain   increases

                    same        again

  5. Variable oxidation states possible

se

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

 

 

 

+1

 

 

 

 

+1

 

 

+2

+2

+2

+2

+2

+2

+2

+2

+2

+3

+3

+3

+3

+3

+3

+3

+3

 

 

 

+4

+4

+4

+4

+4

+4

+4

 

 

 

 

+5

+5

+5

 

 

 

 

 

 

 

 

+6

+6

+6

 

 

 

 

 

 

 

 

+7

 

 

 

 

 

 

Colour: (aquated)                               Colour: (aquated)

Sc3+ → colourless                                                      Ti4+ → colourless

Ti3+ → purple                                                             V4+ → blue

V3+ → green                                                                V2+ → violet

Cr2+ → blue                                                                 Cr3+ → green

Mn3+→ violet                                                              Mn2+→ light pink

Fe2+→ light green                                                      Fe3+ → yellow

Co2+ → pink                                                                Ni2 → green

Cu2+ → blue                                                                Zn2+ → colourless

CHROMATE-DICHROMATE

Preparation: 

begin mathsize 12px style 4 FeCr subscript 2 straight O subscript 4 plus stack 8 text  Na end text subscript 2 CO subscript 3 with left parenthesis Chromite text  ore end text right parenthesis below plus 7 straight O subscript 2 rightwards arrow from Red text  hot in pressce of air end text to 1000 to the power of ring operator minus 1300 to the power of ring operator straight C of 8 text  Na end text subscript 2 CrO subscript 4 plus 2 text  Fe end text subscript 2 straight O subscript 3 plus 8 CO subscript 2 end style

[Lime (CaO) added with Na2CO3 which keeps the mass porous so that air has access to all parts and prevents fusion]

Then, 2Na2CrO4 +H2So4→ Na2SO4↓ +Na2Cr2O7+H2O

                           conc

begin mathsize 12px style open table attributes columnalign right end attributes row cell table attributes columnalign left end attributes row cell It apostrophe straight s text  solubility upto  end text end cell row cell text 32 end text to the power of degree straight C text   end text increases text  and  end text end cell row cell text then decreases end text end cell end table end cell row blank end table close curly brackets end styleHence, suitable temp, is to be employed to crystallise out Na2SO4 first.

Then Na2Cr2O7 is crystallised out as Na2Cr2O7.2H2O On evaporation.

                                                        (red crystal)

How to get

 begin mathsize 12px style straight K subscript 2 Cr subscript 2 straight O subscript 7 comma stack Na subscript 2 Cr subscript 2 straight O subscript 7 with hot space conc. below plus KCl rightwards arrow from decomposition to double of straight K subscript 2 Cr subscript 2 straight O subscript 7 plus 2 NaCl end style

NaCl crystallises out first and filtered off. Then K2Cr2O7 crystallised out on cooling

*        Other props & test of CrO42- & Cr2O72- Already discussed

*        Similarities between hexavalent Cr & S-Compounds.

  1. SO3 & CrO3 → both acidic
  2. S → SO42-, S2O72-, Cr → CrO42-, Cr2O72-
  3. CrO4-2 & SO42- are isomorphous
  4. begin mathsize 12px style SO subscript 2 Cl subscript 2 text  &  CrO end text subscript 2 Cl subscript 2 rightwards arrow with OH to the power of minus on top end style
  5. CrO&  (SO3) has same structure

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