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OQ m.. 88 oe ° T ° 8. Tramsition and Inmer Tramsiti a : Blements 12th Science 12th Chemistry Syllabus 1, Introduction 2. Position in the periodic table 3. Electronic configuration 3.1 Electronic configuration of chromium and copper 4. Oxidation states of first transition series 5. Physical properties of first transition series 6. Trends in atomic properties of the first transition series 6.1 Atomic and ionic radii 6.2 lonisation Enthalpy 6.3 Metallic character 6.4 Magnetic Properties 6.5 Colour 6.6 Catalytic Properties 6.7 Formation of interstitial compounds 6.8 Formation of Alloys 7. Compounds of Mn and Cr (KMn0O, and K,Cr,0.) 7.4 Preparation of potassium permaganate 7.2 Chemical properties of KMnO, 7.3 Uses of KMnO, 7-4 K,Cr,O,: Preparation of potassium dichromate 7.5 Chemical properties of K,Cr,O, 8. Common properties of d block elements g. Extraction of metals 9.1 Metallurgy 9.2 Extraction of Iron from Haematite ore using Blast furnace 40. Inner Transition (f-block) Elements: Lanthanoids and Actinoids 41. Properties of f-block elements 42. Properties of Lanthanoids 42.1 Electronic configuration 42.2 Oxidation state 42,3 Colour and Spectra 42.4 Atomic and ionic radii (Lanthanoid Contraction) 43. Applications 14. Actinoids 15. Properties of Actinoids 16. Applications of actinoids 17. Postactinoid elements | Theory Notes Q. What are d-block element? Q. Explain the position of @-block elements in periodic 2) In these elements last electron table. leash = fess : Q. Give the electronic config- uration of d-block elements. d - Block Elements d d-sub shell in elementary 1) The elements which have partly -_ called d-block Elements. state or common oxidation state (differentiating electron) enters the (n—1)d sub shell i.e. d-sub shell of penultimate shell of the se, Sines ae popaeine othe end of d-series. They do resent end ol c-series 3) on. ne ae - Id, orbital in their clementary State or semen oxidation states. They show sneee ee similar to transition elements, They are considered as transition elements, tabl Position in Periodic Table . 1) d-block elements are placed in the middle of the Loar between 's' and 'p' block eléments because they st how diate properties of s-block and p-block element as Io oe th i) The s-block elements are strongly electropositive while the p-block elements are least electropositive. The d-block element are les than s-block elements and more electropc ; ii) ‘The s-block elements form ionic compounds while the p-block elemetns form covalent compounds. The d-block elements can form both ionic and covalent compounds. Therefore d-block element are.also.called transition-elements. — 2) d-block élements are present in groups from_3 to 12 and periods from 4 to 7. Electronic Configuration of d-Block Elements The general electronic configuration of d-block elements is (n— 1d" ng? There are four series of transition elements. 1. First Transition Series (3d series) 1) It has 10 elements formed by filling up penultimate 3 d orbital gradually. 2) It starts with Sc(Z = 21) and ends to Zn(Z = 30). 3) Its general electronic configuration is [Ar|3d'"'"4s'~, 4) It is present in 4" period. 2. Second Transition Series (4d series) 1) It has 10 elements formed by filling up penultimate 4d orbital gradually. 2) It starts with Y(Z = 39) and ends to Cd(Z = 48). 3) Its general electronic configuration is [Kr]4d'" "5°"? 4) It is present in 5" period. 3. Third Transition Series (5d series) 1) It has 10 elements formed by filling up penultimate 5d orbital gradually. ( ) 2) It starts with La(Z=57) and then in HAZ = 72) to He(Z = 80), cludes elements from 3) Its general electric configuration is [Xe]5d!~°6s? 4) It is present in 6" period. ‘ 4, Fourth Transition Series (6 series) 1) It has 10 elements formed by filling up penultimate 6d orbital gradually. 2) It starts with Ac(Z=89) and the Rf(Z = 104) to Uub(Z = 112). 3) Its general electronic configuration j p-10-762 4) It is present in 7" period. 3 mis RnJed Ts. n includes elements from a Q. Crand Cu show excep- tional electronic configura- tion. Why? Q. Why chromium has elec- tronic configuration 3d°4s' and not 3d'4s°? Q. Why does copper show abnormal electronic configuration? Q. Explain the oxidation states of fist row elements of transition series. OQ. Explain why is F e* more stable than Fe™ ? (Oct. 15, Mark 2) Q. Explain why Mn” ion is more stable than Mn” ? (Given: Mn:Z = 25) (Mar. 14, Mark 1) Q. Write the different oxida- tion states of manganese. Why is +2 oxidation state of manganese more stable? (Mar. 13, Mark 3) 4. Fourth Transition Series ____—_$—_7—scctronie | ae No. ‘ Element Symbol | Atomic °| Configuration | -———_——] 1 ini Tac | 89 [Rn]6d'7s — | _——c7—_|_[rnlst6d"7s" Rutherfordium Rf —— = 105 [Rn]5f'6d°7s* Debeynium Db cere | Seaborgium Sg 106 [Rn — = Bohrium Bh 107 |_ [Rn]5f'6d"7s" _| iy; | 2 Hassium Hs 108 [Rn]5f"*6d°7s ry 4 Meitherium Mt 109 [Rn]5£"6d"7s" Dermstadtium Ds 110 [Rn]5f*6d*7s" Rontgenium Re 111 [Rn]5f6d""7s' Ununbium Uub 112 (Rn]5f*6d"" 7s" Ans. 1) Half filled d-subshell (d) d)have extra stability than incomp! a@ ddd ddd’). 2) Expected and completely filled d-subshell letely filled d-subshell electronic configuration of Chromium (Z=24) is [Ar|3d‘4s’. But the observed electronic configuration of Chromium is [Arl3d°4s'. This is because half filled d° orbital is more stable than incompletely filled d’ orbital. Therefore one electron from 4s orbital is shifted to 3d orbital. ; 3) Expected electronic configuration of Copper (Z = 39) is [Ar]3d°4s? But the observed electronic configuration of Copper is [Ar]3d'°4s' This is because full filled d'°orbital is more stable than incom- pletely filled d° orbital. Therefore one electron from 4s orbital is shifted to 3d orbital. Variable Oxidation States of First Transition Series 1) Oxidation state is the number of charges (+ve or — ve) that an atom of the element appears to have in a molecule. 2) Transition elements show variable oxidation states because (n—1)d and ns orbital have very little energy difference. Therefore electrons from ns and (n—1)d orbital take part in bond formation. 3) The oxidation state of transition elements depends upon the number of electrons in ns orbital and number of unpaired electrons in (n — 1)d orbital. Loss of one 45 electron leads to the formation of M* ion, loss of two 45 electrons gives M” ion while loss of unpaired 3d and 4s electrons gives M”,M" ions and so on. Ex. Scandium (21) has electronic configuration 3d’4s?, Hence it shows +2 and +3 oxidation states. 4) The first and last element of each transition series does not show variable states, because of absence of unpaired d—electrons. 5) Chromium (24) and copper (29) show +1 oxidation state, because their observed outer electronic configuration contain 4s! electron. 6) Ineach transition series, from left to right number of unpaired d— electrons increases up to middle and then decreases. Therefore the elements near to the middle, in each series show maximum oxidation state in compounds like fluorides and oxides. Ex. Mn shows +7 oxidation state. Q. Give the physical proper- ties of first transition series. Q. Explain the trends in atomic properties of the first transition series. Q. Explain the ionization enthalpy of transition elements. 7) Among the variable oxidation states of the same element, some are more stable than other. The oxidation states corresponding to d',d°andd" configurations have extra stability than other oxidation states cnppgce Ex. i) Ti Gd"4s')is more stable than Ti Gd! 4s!) ; ii) Mn” (3d"4s") is more stable than Mn" (3d 4s ) iii) Cu’ Gd'"4s")is more stable than Cu’ (3d’4s°) Groups |3 4 5 6 7 8 9 10 |11 |12 Ele- sc [Ti |v [cr |Mn |Fe |Co | Ni |Cu | Zn ments Oxida- [42 [42 [42 [+1 |+2 ]+2 |42 |42 J+) |? tion 43 |43 [43 [42 [43 [43 [43 [43 [+2 States 44 4a |43 [44 [44 [44 [44 +5 [+4 [45 [+5 +5 | 46 | +6 | +6 [47 _4| Physical Properties of First Transition Series , 1) All the transition elements show metallic properties like mallea- bility, ductility, metallic luster etc. ; 2) Transition elements have high density, high melting point and high boiling point. 3) They are hard and have low volatility. 4) They are good conductors of heat of electricity. 5) All the transition elements (except Zn, Cd, Hg and Mn) have one or more typical metallic structures at ambient temperature. Atomic and Ionic Raddi of First Transition Series 1) As we move from left to right in a transition series, atomic number and hence nuclear charge increases. The last electron enters a penultimate (n—1d) subshell which has poor screening effect due to more diffused shape. As a result atomic and ionic radii decrease gradually across a tran- sition series from left to right. 2) For the same oxidation state, with an increase of nuclear charge a gradual decrease in ionic radii is observed. 3) With higher oxidation state, the effective nuclear charge also increases and hence ionic radii decreases. 4) Ionic radii of transition elements are smaller than ionic radii of representative elements of the same period. Ionization Enthalpy of Transition Elements 1) Ionization enthalpies of transition elements are higher than those of s-block elements and lower than those of p-block elements. This is because the atomic radii and nuclear charge of transition metals lie between those of s-block and p-block elements. 2) The first ionization enthalpies increases with increase in atomic number in a given transition series. But this increase is slow and irregular. This is because, the last electron enters into (n~ l)d subshell which causes screening effect. 3) The first ionization enthalpies of elements of third transition series are higher than those of the elements of first and second transition series. This is because , the elements of third transi- tion series have filled 4f orbitals which cause poor screening effect. This increases nuclear attraction on valence electrons and therefore there is increase in ionization enthalpy. Q. Explain: the compounds of copper (iI) are coloured but those of zinc are colourless. Q. Why is Sc™ colourless while Ti* coloured? (Atomic number Sc=21, Ti=22) (Mar. 16, Mark 2) Q. Explain catalytic proper- ties of transition elements. 5) Transition elements which have completely filled or empty d— sub shell are colourless, Ion (aq.) 3d Electrons Colour Se* 3a° Colourless Ti® 3d! Purple vr 3d? Green cr" 3a° Violet Mn* 3d! Violet Fe** 30° Yellow Co” 3d" Pink Ni? 3a Green Cu” 3d Blue Cut 34" Colourless Zn 3d” Colourless 6) The colour of a transition ion depends on- i) number of unpaired d-electrons. ii) d-d transition iii) nature of ligands i.e. groups attached to metal ion iv) geometry of complex formed by metal ion. Catalytic Properties of Transition Element 1) The substance which increases rate of reaction, but itself remains unchanged at the end of reaction is called catalyst. 2) Many transition metals and their compounds show catalytic properties because of following reason. i) d— block elements have ability to form reaction intermediate with reactants due to variable oxidation states and vacant d— orbitals. This intermediate has lower activation energy and therefore rate of reaction increases. (homogeneous catalysis) ii) d— block elements have ability to absorb reactant molecules on their surface which increases the concentration of reactants and therefore rate of reaction increases. (homoge- neous catalysis) 3) Ex. i) Iron molybdenum (Fe/Mo) is used as catalyst in the synthesis of ammonia by Haber’s process. ii) Platinised asbestos is used as catalyst in the synthesis of sulphuric acid by contact process. iii) Finely divided Ni is used as catalyst in hydrogenation reaction in organic chemistry. Ex. hydrogenation of ethene to ethane at 140°C. iv) Palladium is used as catalyst in hydrogenation of phenol to cyclohexane. v) MnO; is used as catalyst for decomposition of KCIO; to Oo. vi) TiCl, (Ziegler-Natta catalyst) is used in manufacture of high density polythene. vii) Co-Th alloy is used in Fischer Tropsch process in the synthesis of gasoline. Q. What are interstitial compounds? Q. Explain the term Interstitial compounds. (Mar. 16, Mark 1) Q. What is an alloy? Give its | Alloy types and uses. Q. Write the preparation of potassium permagnate. Interstitial Compounds like C,H or N occu 4 ¢ toms li yee PY the hich small 3 f metals is known as inter, The compound in w! lati ‘ oat ‘ lattice 0: interstitial spats oO the cyte iphides and oxides are also trappeq stitial compound. Some’ 5S «. in the crystal lattice of transition element | Compounds pounds and have electrical ang Properties of Interstitia 1) They are hard,lustrous com 1 conductivity. 2) ere iting points are higher than those of pure metals. 3) Their densities are Jower than those of pure parent metals, i | reducing agents. 4) These metal hybrids are powerfu g : 3) Their metal carbides are very hard and chemically inert 6) Their chemical properties are same as that of parent metal. ——————— n which atoms of one metal are randomly fan other metal is calledan alloy. Transition e metals with similar radii and similar Homogeneous mixture i distributed in the lattice o: metals form many alloys. Th properties readily form alloys. Types of alloys There are two types of alloys i) Ferrous alloys In these alloys, atoms 0! atoms of iron. Ex. nickel steel, chr f other elements are randomly distributed in omium steel, stainless steel. ii) Non-ferrous alloys In these alloys, atoms 0! with a non transition element. Ex. brass (alloy of Cu and Zn) f transition metal other than iron are mixed Uses of alloys 1) Bronze (Cu + Sn) is used in making statues, medals and trophies. 2) Cupra - nickel (Cu+ Ni) is used in making machinery parts of marine ships and boats. 3) Stainless steel is used in the construction of the outer fuselage of ultra - high speed air craft. 4) Nichrome (Ni+ Cr in ratio 80: 20) is used in gas turbine engines. 5) Titanium alloys are used for ultra - high speed flight, fire proof bulkheads and exhaust shrouds. Preparation of potassium Permagnete (KMn0,) Deep purple black coloured crystals of potassium permagnate (KMnO,)is prepared from finely divided manganese dioxide (MnO.). It involves following steps Step 1) Preparation of K,MnO, MnO: is fused with alkali KOH in presence of air or oxidizing agent like KCIO, to form green coloured K,MnO, (potassium magnate). 3MnO, + 6KOH + KCIO; > 3K»MnO,+ KCI + 3H20 Step 2) K.MnO, obtained is converted into KMnO, by oxidation or by electrolysis. a) By oxidation K.Mn0O, is oxidized to KMnO, by passing CO, through the solution. b) By electrolytic oxidation K»MnO,is converted into KMnO,by electrolysis using iron elec- trodes separated by a diaphragm. 2K»MnO, + H,0 +[0] — 2KMnO,+ KOH The solution is filtered and evaporated to get KMnO, crystals. 8 Q. Explain the chemical properties of potassium dichromate. Q. What are the common properties of d-block elements? Q. How do metals occur in nature? Q. Define i) Mineral ii) Ore iti) Metallurgy iv) Gangue Chemical Properties of Potassium Dichromate Action on Potassium Iodide _ Acidified potassium dichromate oxidiz S “ while potassium dichromate 1s reduced to solution becomes brown. KiCrpO; + 6KI + 7H2SO, — 4K2SO. + Cr,(SO4), + TH2O + 3In eS potassium iodide to iodine Jaromic sulphate ang Acti Hydrogen Sulphide - _ , When hydrogen eaphide gas is passed into acidified potassium dichromate solution, it is oxidized to sulphur. Potasstum dichromate is reduced to chromic sulphate and becomes green. K.Cr,0; + 4H:$O;+ 3H2S + K2SO. + Cre (SO,), + TH20 + 3S Action on Sulphur Dioxide When sulphur dioxide gas is passe 2 t 1 1 mate solution, it is oxidized to sulphuric acid. Potassium dichro- mate is reduced to chromic sulphate and solution becomes green. KyCrO; + 38, + H2SO. > K2SOu + Cr(SO,), + H20 d into acidified potassium dichro- Physical Properties of d-block Elements ; 1) d-block elements show metallic lustre and shine. 2) They are hard with high melting and boiling points. 3) They have high density. 4) They show good electrical and thermal conductivity. 5) They have high tensile strength and malleability. 6) They can form alloys with transition and non-transition elements. 7) Most of them show catalytic properties. 8) Many metals and their compounds are paramagnetic. Chemical Properties of d-block Elements 1) d-block elements are electropositive metals. 2) They are good reducing agents. 3) They form insoluble oxides and hydroxides. 4) They show variable valencies. 5) They form coloured salts. 6) They form complexes. 7) Fe, Co, Cu, Mo and Zn are biologically important metals. 8) They show biological catalysis. Occurrence of Metals in Nature Metals occur in nature in free state or combined state. i) Free State (Native State) Metals which are non-reactive with air, water and non-metals occur in free state in earth crust. Ex. Gold, silver, platinum. ii) Combined State Reactive metals occur in combined state in the form of compounds with other elements i.e. in the form of oxides, sulphides, carbonates, sulphates, silicates etc. i) Mineral Naturally occurring substance in the earth’s crust which contains metal in free or combined state is called as mineral. It contains inorganic salts, solids, siliceous matter etc. ii) Ore The mineral from which metal can be economically extracted is called as ore. It contains high percentage of metal. All the ores are minerals but all the minerals are not ores. Q. Define a) Hydrometallurgy b) Electrometallurgy (Oct. 15, Mark 2) Q. Which are the various steps involved in the extraction of pure metals from their ores? Q. What is concentration of ores? Q. Write the names and chemical composition of ores of iron. Give the occurrence of iron. Q. How is iron extracted from haematite? 4 Metallurgy € procs ; « 4 : as metallusay, extraction of metal in pure state from its ore is called The: i re are different types of metallurgy as follows- “) Pyrometallurgy re nae of metal from the ore at high temperature using suitable Ing agent is called pyrometallurgy. ») Hydrometallurgy . of metal from aqueous solution of its salts using suitable fucing agent is called hydrometallurgy. c) Electrometallurgy Eatrantion of metal from the ore by electrolytic reduction of molten (fused) metallic compound is called electrometallurgy. iv) Gangue The unwanted impurities like sand, mud etc. present in the ore are called gangue. Ex, Silica is gangue present in haematite ore of iron. Ans. Following four steps are involved in the extraction of from ores- 1) Concentration of ores 2) Conversion of ores into oxides (or other desired compounds) 3) Reduction of ores to crude metals 4) Refining of metals. pure metal Concentration of Ores The process of removal of gangue from the ore is called concen- tration of ore. During concentration, percentage of desired metal increase. There are different methods of concentration of ores. Such as washing, hydraulic classification, magnetic separation, froth floa- tation etc. Occurrence of Iron Iron is the fourth abundant element in the earth’s crust. It occurs in combined state in the form of following ores i) Haematite: Fe.Os ii) Limonite: 2Fe,03.3H,0 iii) Magnetite: FesO. iv) Siderite : FeCOs v) Pyrite: FeS» Extraction of Iron from Haematite Iron is extracted from haematite (Fe:O;). It involves following steps 1) Concentration 2) Roasting 3) Reduction 4) Refining 1) Concentration The lighter gangue present in ore is separated from the heavier ore particles by washing the powdered ore with powerful stream of water. This is called gravity separation. It is done in hydraulic classifier. Q. Write the reaction Chara, RA ato Late ase Ketan —F if \ Z / Slag POivnation—f/ +1200 900 K fi \ Zone of _// _, 1500 at nee taott 1 es) = | CRE 2000 K Vie | t ag Se PS s Molten Iron : Fig : Temperature zones in blast furnace i) Zone of Combustion ; It is the region at 5-10 m from the bottom, In this zone, hot air from the tuyers reacts with coke and forms carbon monoxide. C+50:—- CO AH=-220k) It is exothermic reaction. Hence temperature of this zone is around 2000 K. A part of carbon monoxide dissociates to give finely divided carbon. 2CO —— 02+ 2C Hot gas containing CO and C rises up the furnace. ii) Zone of Reduction involved in the zone of reduc-| It is the region at 22-25 m from the bottom. In this zone, CO and C tion in blast furnace during extraction of tron. (Mar. 15, Mark 2) reduce ferric oxide to spongy iron at about 900 K. Fe.O;+ 3CO —— 2Fe + 3CO: Fe,O;+ 3C —— 2Fe + 3CO iii) Zone of Slag Formation It is the region at 20 m from the bottom. In this zone, following reactions take place. Limestone decomposes to give calcium oxide (quick lime) at about 1200 K. CaCO; —+ CaO + COz Calcium oxide combines with silica and alumina to form slag of calcium silicate and calcium aluminate. CaO + SiO. ——~ CaSiOs 12CaO + 2Al,O; —— 4CasAl0, + 302 iv) Zone of Fusion It is the region at 15 m from the bottom. In this zone, MnO» is reduced to Mn, Cas (PO,), is reduced to P, SiO. is reduced to Si. The spongy iron coming down from the top of the furnace melts and absorbs the impurities like C,Si,Mn,P and S. The molten iron is at the bottom of furnace and lighter slag floats on its surface. The molten iron and slag are removed through separate outlets. The molten iron is cooled in moulds to form solid iron blocks called as pigs. Hence it is called pig iron. It contains upto 4% carbon. 4) Refining Impure iron can be purified by electrolytic refining to obtain pure iron. Q. Give the types of iron. Q. Give the factors that decide the choice of extraction technique to be used Q. What are transition elements? How are they classified? Q. What are f-block elements? (Mar. 16, Mark 1) Q. What are lanthanoids? (Mar. 14, Mark 1) Q. Explain the meaning of i) transition series ii) inner transition series Q. Explain the position of following in periodic table- i) lanthanoids ti) actinoids Q. Give the position of lanthanoids. Types of Iron ; Three forms of iron are commercially used. i) Cast iron (Pig iron) It is hard and brittle iron contail pipes, manufacturing automotive par jning 4% carbon. It is used for making ts, pots, pans, utensils etc. ii) Wrought iron It is soft and pure iron for making pipes, bars han 0.2% carbon. It is used containing less t r S gine bolts and rivetts. for stay bolts, en) iii) Steel ; It is neither too brittle nor too soft ir carbon. Other metals like Mn, Cr and N: alloy steels. It is used in buildings infrastructur mobiles, weapons etc. a Factors that decide the choice of extraction techni 1) Nature of ore. 2) Availability and cost of reducing agent. 3) Availability of hydraulic power. 4) Purity of metal required. 5) Value of byproducts. on containing 0.2% to 2% ij are added to steel to form e, tools, ships, auto- que Transition Elements The elements in which dor f orbit Transition Elements They are divide into two types 1. Main Transition Elements (Transition series) The elements in which (n—1)d orbital is gradually filled are called main transition elements or d—block elements. 2. Inner Transition Elements(Inner transition series) 1) The elements in which (n— 2)f orbital is gradually filled are called Inner Transition Elements or f block elements. 2) They are called as rare earth elements because they are difficult to extract. 3) These elements have outer most two shells incompletely filled i-e. penultimate (n—1)d and prepenultimate (n- 2)f. Inner transition elements consist of two series at the bottom of periodic table. A. Lanthanoids 1) The first series of 14 elements in f - block following lanthanum, (La) at the bottom of periodic table is called Lanthanoids. 2) It starts with Cerium (Ce) with atomic number 58 and ends to Lutetium (Lu) with atomic number 71. 3) It is formed by filling up pre-penultimate 4f orbital progressively. Hence it is also known as 4f series. B. Actinoids 1) The second series of 14 elements in f—bock following actinium (Ac)at the bottom of periodic table is called Actinoids. 2) It starts with Thorium (Th) with atomic number 90 and ends to Lawrencium (Lr) with atomic number 103. 3) It is formed by filling up pre-penultimate Sf orbital progres- sively. Hence it is also known as Sf series. als are gradually filled are called | 4 Position and Electronic Configuration of Lanthanoids 1) All the lanthanoid’s show similarities in their electronic configu- ration and properties. 2) They show maximum oxidation state of +3, Therefore all the lanthanoids belong to IIIB group and 6" period of periodic table. 3) This iseatled 4 f series because they have partially filled (n— 2)4f sub shell. Q. Write a note an colour of lanthanide ions. Q. Why do lanthanoids form coloured compounds? Q. Explain why Gd" is colourless. Q. Define lanthanoid contrac- tion. Explain its effects. (Mar. 15, Mark 3) Q. What is lanthanoid contraction? Explain the cause and effects of lantha- noid contraction. (Oct. 13, Mark 4) Q. Explain, trends in atomic and ionic sizes of lanthanoids. Q. Explain atomic and ionic radii of lanthanoids. Colour of Lanthnoid Jons 1) 2) 3) 4) 5) 6) Ex. Prion has 2 electrons in electrons in 4f orbital ie. (14— 2 Colour of the substance is due to absorption of light. Lanthanoids having incompletely filled f— orbital, absorbs energy from visible range of spectra to promote electrons from lower energy level to higher energy Jevel of the same f—sub shell. This is called f—f transition. Substance shows colour complemen- tary to light absorbed. Lanthnoid metals are silvery white in ¢' Most of the trivalent lanthnoid ions ar and in aqueous solution. Colour of these ions depends upon the number of elect electronic transition in 4f orbital. The colour of lanthnoid ion having nf electron 1s nearly the same as of that lanthnoid having (14— n)f electrons. 4f orbital and Tm = 2electrons. There olour. - , e coloured in solid state rons and * ion has 12 fore Pr* and Tm" have same colour (green). i half filled or full filled 4f orbital are 7) Lanthnoid ion having empty, colourless, because f— f transition is not possible. has half filled f—orbital (f) Ex. Gd" is colourless, because it 8) Ce*and Yb* are colourless because they absorb energy from Lanthanoid Contraction 1) The gradual decrease inate 2) 3) 4) 5) Due to lanthanide contraction, Lee ultra violet light. Lanthanide Ion No. of 4f Color Electrons La* (0) Colourless Ce* 1 Colourless Pr” 2 Green Nd" 3 Pink Pm* 4 Pale yellow Sm* 5 Yellow Eu* 6 Pale pink Gd" @ Colourless Tb* 8 Pale pink Dy” 9 Yellow Ho” 10 Pale yellow Er” ll Pink Tm” 12 Green Yb" 13 Colourless Lu* 14 Colourless omic and ionic radii of f -block elements omic number is called lanthanoid contraction. move from left to right i.e. from Cerium to but electrons are added to with increase in at In lanthanoids, as we Lutetium, atomic number increases, the same inner shell (4f orbitals). This results in increase jn nuclear charge. f— orbital is more diffused in shape and hence it has poor shielding (screening) effect ic. with increase in atomic number, effective nuclear charge increases, but electrons in 4f orbital cover the nucleus poorly from the outermost shell. This causes increase in attraction between nucleus and outermost electrons and decrease in atomic and ionic radii. lanthanides have nearly the gxpla ; nvity of Janthanoids. Q. Give the properties of lanthanoids. Q. What are the applications of lanthanoids? in the chemical reac- | Chemical 7 eC; Same size, TI = ame size, The difficult to separate oe same properties ate from one another. “Therefore they are very : activi , Reaction with ane Fanthanoids When la mperature anthe 3 are they form ace are heated to high temperatur a : " arbides having formula LnC:. Ln+ C —*= Lanthanoid carbide Reaction with nitrogen When la . e nthanoids ar . 4 itri having formula ee heated with nitrogen they form nitrides 2Ln+ No en lanthanoi —s . . having ome ae treated with halogens, they form halides 2Ln + 3X, > 2L0Xs 2Ln + 6HCI — 2LnCl:3H2 — 2LnN Reaction with water When lanthanoids are treated with water, they form basic and ionic ydroxides and evolve H, gas. Ln +3H,O —— Ln(OH), + 3H» Ne Properties of Lanthanoids 1) Lanthanoids are soft metals with silvery white colour and moderate densities of about 7 gm * 2) They are good conductors of heat and electricity. 3) They are non-radioactive (except promethium). 4) Their atomic and ionic radii decrease from lanthanum tolutetium. This is known as lanthanoid contraction. 5) They generally show oxidation number greater than 6 (8 to 12). 6) They are strongly paramagnetic. Heavier lanthanoids become ferromagnetic at lower temperature. 7) Magnetic and optical properties are largely independent of environment. a Applications of Lanthanoids 1) Colour television tube Inner surface of a television tube is coated with tiny patches of three different lanthanoid compositions. when electrons are bombarded on these lanthanoid compounds, they emit visible light and colour image is formed. 2) Optoelectronics , ; . , Lanthanoid jons are used as active ions in luminescent materials. 3) Nd: YAG laser It is neodymium doped yttrium aluminium garnet laser. Communication _ _— . tne - doped fibre amplifiers are significant devices In the optical fibre communication systems. 5) Lanthanoids are used in hybrid cars, superconductors and permanent magnets. Give the applications of getinoids. write a note on postacti- noid elements. Q. What are transuranium elements. Q. Differentiate between lanthanoids and acitnoids. (Mar. 16, Mark 2) (Oct. 15, Mark 2) *y Rete et of Actinoids anise are silvery white in colour. ame ae radioactive and man-made. The, gre less reactive than lanthanoids. 5 points. igh densities with high melting point Tt : ibi cielo ee ie ae oxidation state. They exhibit a7 2 ates from +2 to +8 6 : i A Gone co in the atomic and ionic radii from left to Tight Ce \c to Lw) across the actinoid series is known as actino raction. It is due to the poor shielding effect by f electrons: s and poiling ange of _ Applications of Actinoids Th Gv) oxide, ThO, with 1% CeO. was used as @ oor lighting since these oxides convert heat ener natural gas to an intense light. major source of gy from purning JO ea Fe ee Postactinoid Elements 1) The elements after actinoids (from atomic nu called postactinoid elements. 2) They can be synthesized in nuclear reactions similarly to the actinoids. 3) They have very short half - lives. Ex. half life of element 112 js 2.8 10™'seconds. Hence only a little is known about the chemistry of these elements. mber 104 to 118) are ee Transuranium Elements F The elements after uranium (Z=92) i.e. the elements with atomic number greater than 92 are called transuranium elements. Distinction between Lanthanoids and Actinoids _ Lanthanoids Actinoids 1, Lanthanoids show +2 and| 1. Actinides show +4, +5, +6 and +7 oxidation states in addition to +3 oxidation state. +4 oxidation states 1n addition to +3 oxidation state. 2, In Janthanides 4f 2. In actinides 5f electrons electrons have comparatively have comparatively poor greater shielding effect. shielding effect. 3, They do not form complexes 3. They have greater tendency to form complexes. 4, Their compounds are more basic in nature. easily. 4, Their compounds are less basic in nature. 5. They do not form oxoions. | 5. They form oxoions like UO:,Pu0", NpO> ete. non-radioactive 6. They are radioactive 6. They are (except promethium) elements. 7. They have lower m.p. and 7. They have higher m.p. and b.p. b.p. 8. Most of them are colourless. | 8. Actinoids are coloured 1ons. a Q. Give the similarities between lanthanoids and actinoids. Q. Give the comparison between pre-transition, lanthanoids and transition metals. orbital. 2) highly reactive elements. 4) Both show +3 oxidation state. insoluble. — Comparison between pre-transition, tion metals lanthanoids and transi- Similarities between Lanthanoids and Actinoids 1) In both lanthanoids and actinoids, last electron enters the f— Both lanthanoids and actinoids are highly electropostive and 3) There is poor shielding effect in case of 4f and 5f electrons which causes lanthanoid contraction and actinoid contraction. 5) The nitrates, perchlorates and sulphates of all the elements are soluble while the hydroxides, fluorides and carbonates are Pre-Transition Lanthanoids Transition Metals Metals Essentially Essentially in (+3) | Show variable monovalent - show] oxidation state| oxidation states group (n+) oxidation (+2/+4 for certain state configurations) Periodic trends} Lanthanoid Size changes of dominated by| contraction of Ln’? | M’®less marked effective nuclear charge at noble gas configuration Similar properties| Similar properties Substantial for a given group changes in properties Always ‘hard’ (O, X, Always ‘hard’ (O, X, Heavier metals tion numbers (C.N. properties(C.N. determined by size) determined by size) N. donors, pref-| N donors, pref- (increasingly from erably negatively erably negatively Fe-Cu) may show a charged) charged) ‘soft’ character. No ligand field Insignificant ligand Substantial ligand effects field effects field effects Poor coordination} High coordina-| Coordination number 6 is typical maximum inary exceptions) in| Flexibility in geometry Flexibility geometry Fixed geometries (ligand field effects) No magnetism Show magnetism Show magnetism | 20