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1. INTRODUCTION 2
2. ELECTRONIC CONFIGURATION AND IRREGULARITIES 2
3. GENERAL CHARACTERISTICS 2
4. COLOUR 3
5. COMPLEX FORMATION 3
6. CHROMATE -DICHROMATE 4
7. MANGANATE & PERMANGANATE 5
8. SILVER AND ITS COMPOUND 6
9. ZINC COMPOUNDS 8
10 .COPPER COMPOUNDS 9
11. IRON COMPOUNDS 10
12. INNER TRANSITION ELEMENTS 11
13. LANTHANIDE CONTRACTION 12
1
CONTENTS
S.NO. TOPIC PAGE NO
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d & f - block
1. INTRODUCTIONIn these elements the last electron enters (n1)d orbitals of atom of an element is called d-blockelements.
ELECTRONIC CONFIGURATION AND IRREGULARITIESThe valence shell configurations of these elements can be represented by(n1)d110ns0,1,2 .
All thedblock elements areclassified into fourseriesviz 3d , 4d , 5dand 6d seriescorresponding to thefilling of3d , 4d , 5dand 6dorbitals of (n1)th main shell orbitals of (n1)th main shell. EachSeries has10 elements. Cr(3d5 , 4s 1) , Cu(3d10 , 4s1), Mo(4d5 , 5s1), Pd(4d10, 5s0), Ag(4d10, 5s1)anAu(5d10 , 6s1) clearlyshow the irregularities inthe configurationsThese are explained on the basis of the concept that half filled and completely filled dorbitals arerelativelymore stable thanother dorbitals.
GENERAL CHARACTERISTICS(i) Metallic character: Theyare allmetal and good conductor ofheat & electricity
(ii) Electronic configuration: (n1)d110ns12
2.
3.
Cr Maximum lowest m.p.(iii) M.P. ZnCd
Hg
Mo 6 no. of unpaired e s due to no unpaired e
W are involved in metallic bonding for metallic bonding(iv) Variation inatomicradius:
Sc Mn Fe Co Ni Cu Zn
decreases remains increasessame
(v) Variable oxidation states possibleagain
Sc Ti V Cr Mn Fe Co Ni Cu Zn1 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
7Colour : (aquated)Sc3+
Ti4+
Ti3+
V4+
V3+
V2+
Cr2+
Cr3+
colourless colourless
purpleblue green violetblue green
Mn3+ violetMn2+ light pinkFe2+
Fe3+ light green yellow
Co2+pink
Ni2+
greenCu2+blueZn2+ colourless
2
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4. COLOURSubstancesappearcoloured whenthey absorb light of a particular wavelength inthevisible region of thespectrumand transmit light of other wavelengths.The colourwhich wesee isthecolourof thetransmittedwavelengths. In other words, the colour of the compound observed by us is the complmentary colourof the colour absorbed by the compound.
In thes- and p-block elements there cannot be any d-d transitions and theenergyneeded to promotesor p electronto a higher level is much greaterand maycorrespond to ultraviolet region, in whichcase thecompound willnot appear coloured to the eye.
Relationship between colour and wavelength
Wavelength absorbed in nm
750
Colourabsorbed
UVregionVioletIndigoGreen-blueBlue-greenGreenYellow-greenYellowOrangeRed
Infra-red
Colourobserved
White/colourlessYellow-greenYellowOrangeRedPurpleVioletIndigoGreen-blueBlue-greenWhite/colourless
Magnetic Properties:Whena substance is placed ina magnetic field of strengthH, the intensity of themagnetic field inthe substance maybe greater thanor less thanH.
diamagnetic,Substances whichare weaklyrepelled bya magnetic field
paramagnetic thesubstances whichareweaklyattracted bythemagnetic field and losetheirmagnetism whenremoved fromthe field .
Paramagnetism is expressed bymagnetic moment,
n(n 2) B.M.
n = number of unpairedelectronsB.M. = Bohr Magneton, unit of magnetic moment
5. COMPLEX FORMATIONIn thecaseof transition metals in low oxidation states, the electrons in thed orbitals become involved in
bonding with ligands.The bonding between the ligand and the transition metal ion can either bepredominantly electrostatic or covalent or inmanycases intermediate between thetwo extremes. Some
of the typical complexes of the transition meals are [Fe(CN) ]3,[Ni(NH) ]2 ,[Cu(CN) ]3
,6 3 4 4
[Cu(NH) ]2 etc.3 4
Formation of alloys :
Transition elements have almost similar atomic sizes. Therefore , these elements can mutuallysubstitute their positions in their crystal lattice. The alloys are hard and have high melting points ascompared to the most metal.CatalyticProperties: Many transition metals andtheir compounds have catalytic properties.someexample
TiCl3
V2O5
MnO2
Usedas theZiegler-Natta catalyst in the production of polythene.
Converts SO2 to SO3 inthe contact process for making H2SO4 .
Used as a catalyst to decompose KClO3 to give O2 .
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Fe
H2O2Pd
Pt/Rh
Promoted iron is used in theHaber-Bosch process for making NH3 .
Used as Fentons reagentfor oxidizing alcohols to aldehydes.
Used for hydrogenation (e.g. phenol to cyclohexanone).
Formerly used in the Ostwald process for making HNO3 to oxidize NH3 to NO.
Ni Raney nickel, numerous reduction processes (e.g. manufacture of hexamethylenediamine,production of H2 from NH3 , reducing anthraquinone to anthraquinol in the production of H2O2 ).
Ionisation Energies
Ionisation energies-(i) of 5d elements are higher than those of the 3d and 4d elements. This is due togreatereffective nuclear charge acting on outer valence electrons becauseof theweak shieldingof thenucleus by4felectrons.The ionisation energies of the 3d and4d elements are irregular.
Common oxidation statesfor each element include +2 and +3or both. The+3oxidation states are morestable at the beginning of the series, whereas towards the end +2 oxidation states are more stable.Ionisation energyincreasesgradually from left to right. However the third ionisation energies, when an
electron is removed from 3d orbital, increases more rapidly than the second and third ionisationenergies. Because it takes moreenergy to remove the third electron fromthemetals near theend of therow than from those near the beginning, the metals near the end tends to form M2+ ions rather thanM3+ ions.
6. CHROMATE -DICHROMATEPreparation :
4FeO . Cr2O3+ 8Na2CO3+ 7O2Rosting8Na
2CrO
4+ 2Fe
2O
3+ 8CO
2
in airchromate ore
The roasted mass is extracted withwater when Na2CrO
4goes into the solution leaving behind insoluble
Fe2O
3. The solution is treated with calculated amount of H
2SO
4.
2Na2CrO
4+ H
2SO
4Na
2Cr
2O
7+ Na
2SO
4+ H
2O
Thesolution is concentrated when less soluble Na2SO
4crystallises out.The solution is further concentrated
when crystals of Na2Cr
2O
7areobtained. Then a hot saturated solution of Na
2Cr
2O
7is treated with KCl
when reddish orange crystals of K2Cr
2O
7are obtained on crystallisation.
K2Cr
2O
7is preferred to Na
2Cr
2O
7because Na
2Cr
2O
7is hygroscopic but K
2Cr
2O
7is
not.
* Other props& test of CrO2 & Cr O2 :Alreadydiscussed4 2 7
* Similarities between hexavalent Cr & S-compounds:
(i) SO3& CrO
3both acidic.
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(ii) CrO2 & SO 2 are isomorphous4 4
OH 2 2(iii) SO2Cl2 & CrO2Cl2SO 4 & CrO4 respectively.
OH 2 2(iv) SO3Cl & CrO3Cl SO 4 & CrO4
O
O O|| || ||
(v) CrO3 & (SO3) has same structure Cr O Cr O Cr||O
||O
||O
(vi) Potassium dichromate reacts with hydrochloric acid andevolveschlorine.K
2Cr
2O
7+ 14HCl 2KCl + 2CrCl
3+ 7H
2O + 3Cl
2
(vii) It acts as a powerful oxidisingagent in acidic medium(dilute H2SO
4)
Cr2O 7 + 14H + 6e 2Cr3 + 7H2O. (E = 1.33 V)
The oxidation state ofCr changes from+ 6 to +3.Uses
(i) Asa volumetric reagent in the estimation of reducing agents such as oxalic acid,ferrous ions, iodide ions, etc. It is used asa primary standard.(ii) For thepreparation of several chromiumcompounds such as chrome alum, chromeyellow, chrome red, zinc yellow, etc.(iii) In dyeing, chrome tanning, calico printingphotographyetc.(iv) Chromicacid asa cleansing agent for glass ware.
2 + +
7. MANGANATE & PERMANGANATE
PreparationThis is the most important and well known salt of permanganic acid. It is prepared from the pyrolusiteore. It is prepared by fusing pyrolusite ore either with KOH or K2CO3in presence of atmosphericoxygen or anyotheroxidising agent suchasKNO3. Themass turns green with theformation of potassiummagnate, K2MnO4.
2MnO2+ 4KOH + O
22K
2MnO
4+ 2H
2O
2MnO2+ 2K
2CO
3+ O
2 2K
2MnO
4+ 2CO
2
Thefusedmass is extractedwith water. Thesolution is nowtreated with a current ofchlorine or ozoneor carbondioxide to convert magnate into permanganate.
2K2MnO
4+ Cl
22KMnO
4+ 2KCl
2K2MnO4+ H2O + O3 2KMnO4+ 2KOH + O2
3K2MnO
4+ 2CO
2 2KMnO
4+ MnO
2+ 2K
2CO
3
Props : The above green solution is quite stable inalkali, but inpure water and inpresence of acids,depositing MnO
2andgiving a purple solutionof permanganate.
3K2MnO4+ 2H2O2KMnO4+ MnO2 + 4KOHpurple
= 2.26 V
drak brown
EoEoProb. : ; = 0.56 VMnO2 / MnO2
MnO2 / MnO4 4 4
Prove that MnO2 will disproportionate in acidic medium.4
Another Method of Prepn. : 3K MnO + 2H SO 2KMnO + MnO + 2K SO + 2H O2 4 2 4 4 2 2 4 2
or 3K2MnO4+ 2H2O + 4CO22KMnO4 + MnO2+ 4KHCO3
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1But in the above method of Mn is lost as MnO2but when oxidised either by Cl2 or by O332K
2MnO
4+ Cl
22KMnO4 + 2KCl [Unwanted MnO2 does not form]OR
2K2MnO4 + O3+ H2O 2KMnO4 + 2KOH + O2
200CHeating effect:2KMnO4green K2MnO4 + MnO2 + O2
Black
at red2K2MnO4 2K2MnO3+ O2hotOxidising Prop. of KMnO
4:(in acidic medium)
(i) MnO + Fe+2 + H+Fe+3 + Mn+2 + H O4 2
(ii) MnO + H O + H+Mn+2 + O + H O4 2 2 2 2
(iii) MnO + H SMn2+ + S+ H O4 2 2
In alkaline solution : KMnO4 is first reduced to magnate and then to insoluble manganese dioxide.
Colour changes first frompurple to green and finallybecomes colourless.However brownishprecipitateisformed.
2KMnO4+ 2KOH
2K2MnO4+ 2H2O
2K2MnO
4+ H
2O + O
2MnO2+ 4KOH + 2O
alkaline2KMnO4+ H
2O 2MnO
2+ 2KOH + 3[O]
or 2MnO4 + H2O 2MnO2 + 2OH + 3[O]OxidisingProp.in neutral or weaklyacidic solution:
in presence Zn 2 or ZnO(i) 2KMnO4+ 3MnSO4 + 2H2O 5MnO2+ K2SO4 + 2H2SO4Conversion of Mn+2 to MnO :
4
(i) PbO2
(ii) Pb3O
4+ HNO
3(iii) Pb
2O
3+ HNO
3 (iv) NaBiO
3/ H+
(v) (NH4)2S2O8 / H (vi) KIO4 / H+ +
8. SILVER AND ITS COMPOUND
(I) MetallicAg
In the same way in presence of O2, Ag complexes with NaCN / KCN.4Ag + 8KCN + 2H2O + O24K[Ag(CN)2] + 4KOH
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AgNO3
(Silver Nitrate)
Properties.: (i) It iscalled as lunar caustic because incontact with skinit produces burning sensation like
that ofcaustic soda with the formation of finely devidedsilver (black colour)
(ii) Thermaldecomposition:
(iii) Props. ofAgNO3 : [Already done inbasic radical]
6AgNO3 + 3I2+ 3H2O5AgI + AgIO3+ 6HNO3(excess)
(iv)Ag2SO4 2Ag + SO2 + O2
(v) A(AgNO3)white ppt appears quicklyB
added
ExplainIt takes time to give white ppt.A
added
B(Na2S2O3)
(vi) Ag2
S2
O3
+ H2
O
Ag
2
S + H2
SO4
AgCl .AgBr.AgI (but notAg2S) are soluble in Na
2S
2O
3forming
[Ag(S2O3)2] complexes
(vii)AgBr :AgNO3 KBr AgBr + KNO3
Pale yellow
ppt.
3
2AgNO3 212C 2AgNO2+ O2
2AgNO2 500C 2Ag + 2NO + O2
Heating effect:
(viii)
Ag2O + H2O22Ag + H2O + O2
K2S2O8+ 2AgNO3+ 2H2O2AgO + 2KHSO4 + 2HNO3
Note:
(1) AgO supposed to beparamagnetic due to d9 configuration. But actuallyit isdiamagnetic and exists
asAgI [AgIIIO ]2
(2) Reaction involvedindeveloper :K2Fe (C2O4)2+ AgBrKFe (C2O4)2+Ag+ KBrII III
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9. ZINC COMPOUNDS(1) Zinc oxide, ZnO (Chinese white orphilosopher's wool)
Its foundin nature aszincite orred zinc ore.
Preparation :
(i) 2Zn + O2
2ZnO
(ii) ZnCO3 ZnO + CO2
(iii) 2Zn(NO3)
2 2ZnO + 4NO
2+ O
2
(iv) Zn(OH)2
ZnO + H2O
(a) Physical Properties : It is white powderbecomes yellow onheating again turnswhite on cooling ,insoluble inwater, sublimes at 400C.
(b) Chemical Properties :
(i) ZnO + H2SO
4 ZnSO
4+ H
2O
(iii) ZnO + 2NaOH Na2ZnO
2+ H
2O
400C
(iv) ZnO + H2
(v) ZnO + C
Zn + H2O
Zn + CO
ZnCl2(Zinc Chloride)Preparation: ZnO + 2HClZnCl2+ H2O
ZnCO3+ 2HClZnCl2+ H2O + CO2 It crystallises as ZnCl2 2 H 2OZn(OH) + 2HCl ZnCl + 2H O2 2 2
Anh. ZnCl2cannot be made by heating ZnCl22H2O because
ZnCl22H2O Zn(OH)Cl + HCl + H2O
Zn(OH)Cl ZnO +HClTo get anh. ZnCl
2: Zn + Cl2ZnCl2
Zn + 2HCl(dry)ZnCl2 + H2or Zn + HgCl2 ZnCl2 + Hg
Properties:(i) It is deliquescent white solid (whenanhydrous)(ii) ZnCl
2+ H
2S ZnS
"
"
+ NaOHZn(OH)2excess Na2[Zn(OH)4]
+ NH4OHZn(OH)2 excess [Zn(NH3)4]2+
Uses:1]2]
3]
Used for impregnating timber to prevent destruction byinsectsAs dehydrating agent when anhydrousZnOZnCl
2used indental filling
ZnSO4 (Zinc Sulphate)Preparation:
Zn + dil H2SO4ZnSO4 + H2
ZnO + dil H2SO4 ZnSO4+ H2OZnCO3+ dil H2SO4ZnSO4+ H2O + CO2
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ZnS 2O2 ZnSO 43
ZnS + O ZnO + SOparallel reaction
2 2 2
ZnS + 4O3ZnSO4+ 4O2
70C 280C3970CProps. 1] ZnSO47H2O ZnSO46H2OZnSO4H2OZnSO4
1
2O
2+ SO
2+ ZnO
Uses: 1]2]
ineye lotionLithophone making (ZnS + BaSO
4) aswhite pigment
COMPOUNDS10. COPPER
CuO :
Preparation: (i) CuCO3.Cu(OH)2 2CuO + H2O + CO2 (Commercial process )Malachite Green(native Cu-carbonate)
12Cu + O
22CuO & Cu2O + 2O22CuO(ii)
(iii)
(iv)
Cu(OH)2 CuO + H2O
2Cu(NO3)2 250C 2CuO + 4NO2+O
2
Properties: (i)
(ii)CuOisinsoluble in waterReadily dissolves indil. acids
CuO + H2SO4CuSO4+ H2OHCl CuCl2HNO
3Cu(NO
3)
2
It decomposeswhen, heated above 1100C4CuO 2Cu2O + O2CuO is reduced to Cu by H2 or C under hotconditionCuO + CCu + COCuO + H
2Cu + H
2O
(iii)
(iv)
CuCl2:Preparation: CuO + 2HCl(conc.) CuCl2 + H2O
Cu(OH)2CuCO
3+ 4HCl 2CuCl
2+ 3H
2O + CO
2
Properties: (i)(ii)
It is crystallised as CuCl22H2O ofEmerald green colour
dil. solution inwater is bluein colour due to formation of[Cu(H
2O)
4] complex.
conc. HCl or KCl added to dil. solution of CuCl2 the colour changesinto yellow, owing to the formation of [CuCl4]The conc. aq. solution is green incolour havingthe twocomplex ions in
equilibrium 2[Cu(H2O)4]Cl2 l [Cu(H2O)4] + [CuCl4] +4H2OCuCl2 CuCl byno. of reagents
2+
(iii)2
(iv)
2+ 2
(v)
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(a) CuCl2 + Cu-turnings 2CuCl(b) 2CuCl
2+ H
2SO
3+ H
2O 2CuCl + 2HCl + 2H2SO4
(c) 2CuCl2 + Zn/HCl 2CuCl+ ZnCl2(d) CuCl2 + SnCl2CuCl + SnCl4
** CuF22H2O light blue
CuCl22H2O greenCuBr2 almost black
CuI2 doesnot exist
Anh. CuCl 2is dark brown mass obtained
by heating CuCl22H2O at 150C in presenceof HCl vap.
150CHClgas
CuCl22H2O CuCl2 + 2H2O
CuSO4:
Preparation: CuO + H2SO4(dil)CuSO4 + H2O Cu(OH)2 +H2SO4(dil) CuSO4 + 2H2O Cu(OH)2CuCO3 +H2SO4 (dil)CuSO4 + 3H2O + CO2
1Cu + H
2SO
4+
2
O2CuSO4 + H2O [Commercial scale]
(Scrap)Cu + dil. H2SO4 no reaction {Cu is a below H inelectrochemical series}It iscrystallised as CuSO45H2OProperties:(i)
(ii) CuSO45H2O
Blue
CuSO43H
2O
Pale blue
CuSO4H
2O
Bluish whitetake places
CuSO4(anh.)white
(iii) Revisionwithall others reagent
11. IRON COMPOUNDS
FeSO47H
2O:
Preparation: (i) Scrap Fe + H2SO4FeSO4+ H2
(dil.)From Kipp's waste
FeS + H2SO
4(dil)FeSO
4+ H
2S
7FeS
2+ 2H
2O +
2O
2FeSO4+ H2SO4
(ii)
(iii)
Properties: (i) It undergoes aerial oxidation forming basic ferric sulphate4FeSO
4+ H
2O + O
2 4Fe(OH)SO
4
FeSO 4 high Fe O +SO +SO300C(ii) FeSO47H
2O anh.white 2 3 2 3temp.
(iii) Aq. solution is acidic due to hydrolysisFeSO
4+ 2H
2O l Fe(OH)
2+ H
2SO
4
weak base
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(iv) It isa reducing agent(a) Fe2+ + MnO + H+Fe3+ + Mn2+ + H O
4 2
(b) Fe2+ + Cr O 2+ H+Fe3+ + Cr3+ + H O2 7(c) Au3+ + Fe2+Au + Fe3+
(d) Fe2+ + HgCl Hg Cl + Fe3+
2
2 2 2
white ppt.
(v) It forms double salt. Example (NH4)2SO4FeSO46H2O
FeO(Black):
FeC O FeO + CO + COPrepn : 2 4 2in absence of air
Props: It is stable at high temperature and on cooling slowlydisproportionates into Fe3O4 andiron
4FeOFe3O4+ FeFeCl
2:
Prepn: heatedin a current of HCl
OR
Fe + 2HCl FeCl + H2 2
2FeCl3+ H
2 2FeCl2+ 2HCl(i) It is deliquescent in air like FeCl3(ii) It is soluble inwater, alcoholandether also because it is sufficientlycovalent in nature(iii) It volatilises at about 1000C and vapour density indicates the presence of Fe
2Cl
4.
Above 1300C density becomes normal(iv) It oxidisesonheating inair
12FeCl2+ 3O22Fe2O3+ 8FeCl3(v) H2 evolves on heating in steam
3FeCl2+ 4H2O Fe3O4+ 6HCl + H2(vi) It can exist as different hydrated form
FeCl22H2O colourlessFeCl
24H
2O pale green
FeCl26H2O green
Props:
FeCl3:
Prepn: Anhydrous ferric chloride isprepared byheating metallic iron ina stream of drychlorine gas.(i) FeCl
3solid isalmost black. It sublimes at about 300C,giving a dimeric gas.
(ii) FeCl3 dissolvesinbothether and water, giving solvated monomeric species.(iii) Iron (III) chloride isusuallyobtained as yellow-brown lumps of the hydrate FeCl
36H
2O.
(iv) Thisisverysolubleinwaterand isusedbothasanoxidizing agent, and asa mordant indyeing.(v) FeCl3 is also used in themanufacture of CCl4.
12. INNER TRANSITION ELEMENTSThe elements in which theadditional electrons enters (n2)forbitals arecalledinner transition elements.The valence shell electronic configuration of these elements can be represented as
(n2)f0,2...14(n1)d0,1,2,ns2 .These are alsocalled f-blockelementsbecause the extra electron goes
to f-orbitals which belongs to (n2)th mainshell. 4f-block elements are also called lanthanides orrare
earths. Similarly5f-block elements arecalled actinides or actinones. Thename Lanthanides and actinideshave been given due to close resemblance with Lanthanum and actinium respectively. Lanthanides
constitutes the first inner transition serieswhile actinides constitutes secondinner transition series.
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d & f - block
General Characteristics:
1. Electronic Configuration
[Xe] 4fn 15d0 6s2 or[Xe] 4fn 5d16s2
Oxidation state: TheyreadilyformM3 ionssomeofthemalsoexhibit oxidationstate of+2and +4.
Colouration: IonsofLanthanides and actinides are coloured in the solid state aswell as in aqueous
2.
3.solutionbecause of absorbation of light due to ff transition since theyhave partlyfilled f-orbitals.
13.LANTHANIDE CONTRACTIONIn lanthanides, the additional electron enters 4f-sub shell but not in the valence-shell namely sixth shell.
The shieldingeffect of one electron in4f-sub-shell by another inthe same sub-shell isverylittle, being
evensmaller thanthat of d-electrons, because the shape of f-sub shell isvery muchdiffused, while there
isnocomparable increase inthemutual shielding effect of4f-electrons.This results inthat electrons inthe
outermost shellexperience increasing nuclear attraction from the growing nucleus.Consequently the
atomic and ionic radii go on decreasing as wemove fromLa57
to Lu71
.
Consequence of Lanthanidecontraction
1. Atomic andionic radii of post-Lanthanide elements: The atomicradii of second rowtransition
elements arealmost similar to thoseofthe third row transitionelement because the increase insize on
movingdownthegroup fromsecondto third transition elements iscancelled bythedecrease insize
due to lanthanide contraction.
High density of post lanthanide elements:It is because of very small size due to lanthanide
contraction.
Basic strength of oxides and hydroxides: Due to lanthanide contraction the decrease in size of
2.
3.
lanthanides ions, from to increases the covalent character (i.e. decreases the ionicLa 3 Lu 3
character) betweenLn3 andOH ions inLn(III) hydroxides (Fajans rules). Thus La(OH) is the3
most basic while Lu(OH)3 is the best basic.
Similarly, there isa decrease inthe basic strength of theoxides.
Seperation of Lanthanides: Due to the similar size (Because of lanthanide contraction) of the
lanthanides, it isdifficult to separate them. But slight variationintheir properties isutilizedto separate
4.
Consequences of Lanthanide Contraction
(i) Separation of Lanthanides.Separationof lanthanides ispossibleonlydue to lanthanide contraction.
All thelanthanideshave quite similar properties anddue to this reason theyaredifficult to separate.
However, because of lanthanidecontraction their properties (such as ability to formcomplexes)varyslightly. Thisslight variation inproperties isutilized intheseparationoflanthanidesbyionexchange
methods.
(ii) Variation in basicstrength of hydroxides. Thebasic strength of oxides andhydroxides decreasesfrom La(OH)3to Lu(OH)3. Due to lanthanide contraction sizeof M3+ ionsdecreases and there is
increase in the covalent character in MOH bond.
(iii)Similarity of second and third transitionseries. The atomic radii of second rowof transition
elements are almost similar to those of the third rowoftransition elements. For example, among the
elements of group 3, there is normal increase insize fromSc toYto La. But after lanthanides the
atomic radii fromsecond to third transitionseries do not increase as shownbelowfor group 4 and
group 5 i.e., for Zr HfandNb Ta pairs whichhave element same atomic radii.Aftergroup 5 the
effect oflanthanide contraction isnotso predominant.
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5. Colour. The lanthanide metals aresilverywhite metals and the trivalent lanthanide ions arecoloured
both in thesolid state and inthe aqueoussolution.
La3+ (4f0) and Lu3+ (4f14) having no unpaired electron do not show6. Magnetic properties.
paramagnetism whileallother tripositive ions of lanthanides areparamagnetic.
They have lowionisation energyandarehighlyelectropositive.Their ionisationenergyvalues are
quite comparable withthose of alkaline earth metalsparticularlycalcium.These metalsdo not have muchtendencyto form complexes.
The lanthanidesarehighlyreactive. Thisisinagreement withthe lowvaluesoftheir ionisationenergies
andelectronegativity.
7.
8.
9.
10. Thesolubilityof compoundsof lanthanidesfollowthesameorder asgroup 2 elements.Their fluorides,
oxides, hydroxides, carbonates are insoluble inwater. However halides (except fluorides), nitrates,
acetates aresoluble inwater.
General Characteristics ofActinides 5f Block Series Second InnerTransition Series
1.
2.
These aresilverywhitemetals with highmelting and boiling points.
Besides the most common oxidation state of +3, actinides show +4, +5 and +6oxidation states incertainelements.
All the actinides are radioactive innature.
All theactinides are highlyelectropositive and assuch arestrong reducingagent.Actinides have a strong tendency towards complex formationand form oxocations like UO22+,PuO22+, UO+ etc.
Most of the cationsof actinides are coloured.
Actinidesshow actinide contraction i.e., decrease inionic radiialong theseries.
3.
4.
5.
6.
7.
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Ex.1 On what basis can you say that scandium(Z = 21) is a transition element but since
(Z = 30) is not.
On the basis of i incompletely filled3d - orbitals in case of scandium atom in itsground state 3d1), it is regarded as a transitionelement. On the other hand, zinc atom hascompletelyfilled d- orbitals (3d10) in its groundstate as well as in its oxidisedstate, hence it isnot regarded as transition element.
(b) because Ce(IV) has extra stability due toempty f0 orbital.
Ce3+Ce4+ + e
[Xe] 4f1 5d06s0Sol.(c) InMn2+ d5 configuration leas to extra
stability of half filled configuration , so Mn2+/Mn2+(d4) tends to get converted to stable d5,configuration of Mn2+, by accepting an electronso Mn3+/Mn2+ redox couple has more positive
potential than Fe3+/Fe2+(d14) couple.
(d) Due to more negative enthalpy of hydrationof Cu (aq) than Cu (aq) which compensatesor second ionization enthalpyof copper.
(e) In the third transition series after lanthanumtheir is lanthanoid contraction due to ineffectiveshielding by intervening f-orbital electrons andhence second and third transition serieselements have similar atomic radii.
Ex.2 What is the effect of increasing pH on K2Cr
2O
7
solution?
Inaqueoussolution, wehave
2+ +
Sol. Cr2O
7+ H
2O2 2CrO
4+ 2H .2 +
When pH < 4 (acidic medium), it exists asCr
2O
7 and the colour is orange.
When pH> 7 (basic medium), it exists asCrO4 and thecolour isyellow.
What is the basic difference between theelectronicconfigurationsof transitionandinnertransitionelements.Generalelectronic configuration of transition
element = [ Noblegas] (n 1) d110 ns12 andfor inner transition elements
=(n2) f 114 (n 1)d01ns02. Thus , in transitionelements, last electron enters d-orbitals of the
penultimate shelll while in inner transitionelements, it enters f- orbital of thepenultimateshell.
2
2
Ex.5 WhyisCr2+ reducing and Mn3+ oxidising whenbothhave d4 configuration?
Cr2+ is reducing as its configuration changesform d4 to d3, the later hashalf filled t level.
Ex.3
Sol.
2g
Again thechange fromMn2+ toMn3+ results inthehalffilled (d5) configuration whichhas extrastability.
Sol.
Ex.6
Sol.
Cu+ ionisnot stable inaqueous solution.Why?Cu2+ (aq) is much more stable than Cu+(aq).This is because although second ionization
enthalpyof copper is large but H for Cu2+hyd(aq) ismuch more negative than that for Cu+
(aq) and therefore it more than compensatesfor the second ionization enthalpy of copper.
Thus many copper (I) compounds ar unstablein aque o us so lu t io n and und er go esdisproportionalas follows.
2Cu+ (aq) Cu2+(aq) + Cu(s)
Ex.4 Give reasons for thefollowing(a) Transition metals have high enthalpies of
atomizations.(b) Among the lathanoids, Ce(III) is easilyoxidised to Ce(IV)(c) Fe3+ | Fe2+ redox couple has lesspositiveelectrodepotential thanMn3+| Mn2+ couple.(d) Copper (I) has configuration , stillcopper (II) hasd9 configuration stillcopper (II)ismorestable inaqueous solution than copper(I).
(e) The second and third transition series
elements have almost similar atomic radii.(a) Due to strong interatomic interactionbetween valence electrons.
d10 Ex.7 Why is the E value for the M3+/ M2+ couplemuch more positive than that of Cr3+/Cr2+ or
Fe3+/Fe2+? Explain.
Much larger third ionization energy of Mn(Where therequiredchange is d5 tod4) ismainly
responsible for this.This also explainswhythe+3stateofMn is oflittle importance.
Sol.
Sol.
14
SOLVED EXAMPLES
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Ex.8 Why does Mn (II) ion show the maximum Q.13 Arranged the following in increasing order of
acdic character:
CrO , CrO, Cr O
paramagnetic behvavious among bivalent ionsof thefirst transitionseries.?The electronic configurations ofMn and Mn
(II) ionare
25
Mn: 1s 2s 2p 3s 3p 3d 4s ,Mn+2 : 1s2,2s22p6 3s23p63d24s0
The Mn+2 ionhas fiveunpairedelectrons inits3d subshell which is the maximum value for atransition metal ion. Hence, Mn(II) shows themaximum paramagnetic behaviour (due tounpaired electrons) among bivalent ions of thefirst transition series.
2
CrO< Cr O y(B) compounds in oxidation state x are ionicifx < y(C)compounds inoxidation state yare covalentif x < y(D) compounds inoxidationstate yarecovalenti f y
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EXERCISE - IIQ.1
Q.2
Q.3
Formation of MnO42+Due to disproportionation of Hg2
NH3 - strongligand causespairing of electrons.So complex isdiamagneitc. Fisa weak ligand and so
pairing isnot possible.
[Al(OH)3 and NaAlO2; Zn(OH)2 and Na2ZnO2] also [Zn(NH3)4]2+
[Zn S iswhitebut PbS isblack].
[A] = ZnCl2; [B] = Zn(OH)2; [C] = Na2ZnO2; [D] = ZnS; [E] = AgCll
All the three elements haved10
See text for the reaction of HCland KMnO4
.
[(A) = ZnSO3; (B) = ZnO ; (C) = SO2; (D) = ZnS]
3/2 M
K2[Pt Cl6]
Clis a weak ligandso no pairing of electrons. CO is a strong field ligand and, therefore, causespairing ofelectrons.
In the first case, a double salt is formed. In the second case, a complex is formed. So no test.
(A) = [Cr(H2O)6]Cl3 ; (B) = [CrCl(H2O)5]Cl2 H2O (C) = [Cr Cl2(H2O)4]Cl2.2H2O
(A) = [Cr(NH3)4 ClBr]+ Cland (B) = [Cr(NH3)4Cl2]
+ Br.
[Co(NH3)4 Cl(H2O)] SO4 ;[Co(NH3)4(SO4)(H2O)]Cl [Co(NH3)4(SO4)(Cl)] H2O
Q.4
Q.5
Q.6
Q.7
Q.8
Q.9
Q.10
Q.11
Q.12
Q.13
Q.14
Q.15
Q.16
EXERCISE - III
Q.1
Q.6
Q.11
Q.16Q.21
Q.26
Q.31
Q.36
Q.41
Q.46
Q.51
Q.56
A
B
B
CA
A
C
A
A,B
A,B,C
A,B,C,D
B
Q.2
Q.7
Q.12
Q.17Q.22
Q.27
Q.32
Q.37
Q.42
Q.47
Q.52
Q.57
B
A
A
AD
C
A
B
A,B
A,B
A,B
A
Q.3
Q.8
Q.13
Q.18Q.23
Q.28
Q.33
Q.38
Q.43
Q.48
Q.53
Q.58
A
A
B
BA
D
D
A,B,C
B,C
B,C
A,B,C
C
Q.4
Q.9
Q.14
Q.19Q.24
Q.29
Q.34
Q.39
Q.44
Q.49
Q.54
Q.59
B
B
D
AB
C
A
B,C,D
A,B,C
A,C
A,B
B
Q.5
Q.10
Q.15
Q.20Q.25
Q.30
Q.35
Q.40
Q.45
Q.50
Q.55
Q.60
A
A
B
D
D
B
A
A,B
A,B,C
A,B
B,C
C
ANSWER KEY