8 D and F Block elements. Class 12th Chemistry Chapter pptx

D AND F BLOCK ELEMENT CHEMISTRY CLASS 12TH

1. Prepared by Mr. Sandeep Kumar PGT CHEMISTRY KV RECKONG PEO,KINNAUR HIMACHAL PRADESH CHAPTER-4 The d and f Block Elements CLASS-XII

2. The transition elements (d-block) Introduction d-block elements : Elements belonging to group 3 to12 of the periodic table are known as d-block elements. In these elements last electron enter into penultimate d-orbital. d-block elements lie between s and p-block elements.

3. Periodic table

4. Transition series

5. Transition series d-block consists of four transition series 1 st Transition series or 3d series 21 Sc to 30 Zn 2 nd Transition series or 4d series 39 Y to 48 Cd 3 rd Transition series or 5d series 57 La, 72 Hf to 80 Hg 4 th Transition series or 6d series 89 Ac, 104 Rf to 112 Cn

6. Transition Elements Transition elements: Element which has partially filled penultimate d-subshell in ground state or most common oxidation state are known as transition elements. All d-block elements are not transition elements but all transition elements are d- block elements. Transition elements have partially filled d- subshell in ground state or most common oxidation state .But all d-block elements not follow this. Zn, Cd & Hg are not considered as transition metals .

7. General Electronic Configuration (n-1)d 1-10 ns 1-2

8. General properties of transition elements Magnetic properties. Coloured ions. Formation of complexes Catalytic properties Formation of interstitial compounds. Oxide formation. M.p & B.p Atomic and ionic size Ionisation enthalpy Oxidation state Standard electrode potential. Reactivity

9. Melting and Boiling Point Melting and Boiling Point: Generally High d block elements have large no. of unpaired electrons hence they form strong metallic bond. Their melting and boiling points are high . Specific cases: Exceptionally Zn ,Cd and Hg have low melting and boiling point. Mn and Tc have abnormally low m.p. Group 6 elements have highest m.p in corresponding period (Cr, Mo, W). Tungsten has highest m.p among metals.

10. Melting points Trends of melting points of transition elements

11. Variation in atomic and ionic radii Atomic size decreases left to right. Increases at the end of series. 4d & 5d series have almost same size.(due to lanthanoid contraction)

12. Ionisation Enthalpy Generally increases due to increases in nuclear charge from left to right in series . IE 1 <IE 2 < IE 3 in each group due to positive charge on them. IE 1 of 5d series is much higher than those of 4d and 3d due to weak shielding by 4f electrons.

13. Oxidation State Transition elements have variable oxidation state , due to very small energy difference between(n-1)d and ns subshell . Electrons from both the subshell take part in bonding. No. of Oxidation states α no. of unpaired electrons . Mn shows all oxidation states from +2 to +7 .

14. Variation in oxidation state Low oxidation state are found when a complex compound has ligands capable of π -acceptor character in addition to the sigma bonding, e.g. Ni(CO) 4 , Fe(CO) 5.

15. Standard electrode potential Value of electrode potential depends on enthalpy of atomisation , sum of ionisation enthalpies and hydration enthalpy. Reduction potential α Δ a H α I.E α 1/ Δ hyd H Due to positive electrode potential, Cu does not liberate hydrogen from acids . It must be noted that the value of E for Mn , Ni and Zn are more negative than expected from the trend.

16. Standard electrode potential

17. Reactivity Though the transition elements are moderately electropositive, yet they are not very reactive because of their ( i ) High heat of sublimation (ii) High ionisation enthalpy

18. Reactivity

19. Magnetic Moment Transition metals and compounds are paramagnetic due to the presence of unpaired electrons in their d-subshell. Substances which do not contain unpaired electrons and repel by magnetic field are dia -magnetic. Weakly attracted-----Paramagnetic Strongly attracted-----Ferromagnetic The spin only magnetic moment can be calculated by the formula µ=√ n(n+2) BM where n is the no .of unpaired electrons.

20. Magnetic Moment

21. General Properties of d-Block elements

22. Outline General characteristics of d-Block elements: Formation of coloured ions. Formation of complex compound. Catalytic property. Formation of interstitial compounds. Alloy formation.

23. Formation of Coloured compounds Most of the transition metal compound are coloured both in solid state and in aqueous solution. Generally atoms or ions have unpaired electrons. Due to d- d transition produce coloured compound.

24. Coloured ions

25. Complimentary colour chart

26. Standard reduction potential of higher oxidation states

27. Complex Formation The tendency to form complex compounds is due to- Small size of the ion High charge on the transition metal ion. The availability of d orbitals for accommodating electrons donated by the ligands. Cu 2+ ( aq ) + 4 NH 3 ( aq )  [Cu(NH 3 ) 4 ] 2+ ( aq ) (blue) (deep blue) AgCl (s) + 2 NH 3 ( aq ) → [Ag (NH 3 ) 2 ]Cl ( aq ) (white ppt) (Colourless )

28. Catalytic Properties Their catalytic properties are due to- • Presence of unpaired electron in their incomplete d-subshell. • Variable oxidation state of transition metal and ability to form complexes . In most cases provide large surface area with free valency .

29. Interstitial Compounds Due to void space of suitable size in their lattices, small atoms can be easily accommodated.

30. Alloy formation Most of transition metals form alloys because of their  similar radii due to which transition metals can mutually substitute their position in their crystal lattice.

31. Formation of Oxides Transition metals form oxides of general composition MO, M 2 O 3 , MO 2 and MO 6 , etc. Lower oxidation state: Basic Higher oxidation state: Amphoteric or Acidic MnO Mn 2 O 3 ,Mn 3 O 4 ,MnO 2 Mn 2 O 7 Basic Amphoteric Acidic

32. Some important compounds of transition elements

33. Outline Potassium dichromate: Methods of preparation , Properties and Uses. Potassium permanganate: Methods of preparation , Properties and Uses. Structure of Permanganate and Dichromate ions.

34. Potassium dichromate ( K 2 Cr 2 O 7 ) Preparation: From Chromite ore ( FeCr 2 O 4 ) 4 FeCr 2 O 4 + 8 Na 2 CO 3 + 7O 2 8 Na 2 CrO 4 + 2 Fe 2 O 3 + CO 2 (chromite ore) 2 Na 2 CrO 4 + H 2 SO 4 → Na 2 Cr 2 O 7 + Na 2 SO 4 + H 2 O Na 2 Cr 2 O 7 + 2 KCI → K 2 Cr 2 O 7 + 2 NaCl Orange crystals of K 2 Cr 2 O 7 are obtained on crystallisation .

35. Properties of potassium dichromate   Physical Properties :  Orange-red coloured crystalline compound. Moderately soluble in cold water but freely soluble in hot water. It melts at 398°C. K 2 Cr 2 O 7 is preferred over Na 2 Cr 2 O 7 as a primary standard in volumetric estimation because Na 2 Cr 2 O 7 is hygroscopic in nature but K 2 Cr 2 O 7 is not.

36. Effect of pH on Potassium dichromate Cr 2 O 7 2- + 2 OH - → 2 CrO 4 2- + H 2 O (Orange) (Yellow) 2 CrO 4 2- + 2 H + → Cr 2 O 7 2- + H 2 O (Yellow) (orange)

37. Oxidising nature of Potassium dichromate Powerful oxidising agent in acidic medium (dil. H 2 SO 4 ) Cr 2 O 7 2- + 14H + + 6e - → 2Cr 3+ + 7H 2 O (E° = 1.33 V) 6Fe 2+ + Cr 2 O 7 2- + 14 H + → 6Fe 3+ + 2Cr 3+ + 7H 2 O 6I - + Cr 2 O 7 2- + 14 H + → 3I 2 + 2Cr 3+ + 7H 2 O 3Sn 2+ + Cr 2 O 7 2- + 14 H + → 3Sn 4+ + 2Cr 3+ + 7H 2 O 3H 2 S + Cr 2 O 7 2- + 14 H + → 3S + 2Cr 3+ + 7H 2 O Note: Oxidation state of Cr changes from +6 to +3

38. Uses Of Potassium Dichromate Used as a primary standard in volumetric analysis for the estimation of reducing agents such as oxalic acid, ferrous ions, iodide ions, etc. F or tanning of leather, calico printing, photography etc. As a cleansing agent for glass ware in the form of chromic acid.

39. POTASSIUM PERMANGANATE ( KMnO 4 ) POTASSIUM PERMANGANATE (KMnO 4 ) Preparation: From pyrolusite ore(MnO 2 ) 2MnO 2 + 4KOH + O 2 → 2K 2 MnO 4 + 2H 2 O (K 2 MnO 4 → 2K + + MnO 4 2- ) 3MnO 4 2- + 4H + → 2MnO 4 - + 2H 2 O + MnO 2

40. Properties Physical Properties : It is purple coloured crystalline compound. Sparingly soluble in water at room temperature. Chemical Properties : Effect of heating 2KMnO 4 751K K 2 MnO 4 + MnO 2 + O 2

41. Effect of pH MnO 4 - OH- MnO 4 2- H+

42. Oxidising nature of KMnO 4 KMnO 4 shows strong oxidising nature. It shows different oxidising nature in different medium. Acidic medium: MnO 4 - + 8H + + 5e - → Mn 2+ + 4H 2 O Neutral or faintly alkaline medium: MnO 4 - + 2H 2 O + 3e - → MnO 2 + 4OH - Strongly alkaline medium: MnO 4 - + e - → MnO 4 2-

43. Oxidising nature of KMnO 4 In acidic medium (presence of dil. H 2 SO 4 ) : MnO 4 - + 8H + + 5e - → Mn 2+ + 4H 2 O 5Fe 2+ + MnO 4 - + 8H + → 5Fe 3+ + Mn 2+ + 7H 2 O Iodide is oxidised to Iodine H 2 S is oxidised to Sulphur SO 2 is oxidised to H 2 SO 4 Nitrite(NO 2 - ) is oxidised to Nitrate(NO 3 - ) Oxallic acid is oxidised to CO 2 This reaction is slow at room temperature, but is rapid at 60°C. Mn(II) ions produced catalyse the reaction; thus the reaction is autocatalytic.

44. Oxidising nature of KMnO 4 In slightly alkaline & neutral medium : In slightly alkaline medium KMn0 4 is reduced to MnO 2 (MnO 4 - to MnO 2 ) 2 MnO 4 - + I - + H 2 O → 2 MnO 2 + IO 3 - + 2 OH - 8 MnO 4 - + 3 S 2 O 3 2- + H 2 O → 8 MnO 2 + 6 SO 4 2- + 2 OH - Point to be noted: Permanganometric titrations in the presence of HCl are unsatisfactory as HCl is oxidised to chlorine by KMn0 4 .

45. Uses of KMnO 4 Used as an oxidising agent in laboratory and industry. Alkaline potassium permanganate is called Bayer's reagent. This reagent is used in organic chemistry for testing unsaturation. KMnO 4 is used in the manufacture of saccharin, benzoic acid, acetaldehyde,etc . KMnO 4 is used as a reagent in qualitative analysis and as primary standard in quantitative analysis. KMnO 4 is used as an antiseptic

46. Structure of ions

47. The Inner transition elements(f-block)

48. OUTLINE General electronic configuration. General properties of inner transition elements. Lanthanide and Actinide contraction. Properties of lanthanides and Actinides Uses of Lanthanides and Actinides Difference between lanthanides and actinides

49. Introduction of f-block elements Inner transition elements(f -Block elements): They are present in separate block in the periodic table. Last electron enters in pre-penultimate f-subshell, so they are known as f-block elements. Lanthanoids: last electron enters one of the 4f orbital. Cerium(at. No. 58) to Lutetium(at. No.71) Actinoids: last electron enters one of the 5f orbital. Thorium (at.no.90)to lutetium(at. No.103) They are also known as ‘inner transition elements’.

50. Lanthanoids

51. Lanthanoids General electronic configuration: 4f 1-14 5d 0-1 6s 2 last electron enters one of the 4f-orbitals, so they are known as f-block elements. Lanthanoids are Ce(at. No. 58) to Lu(at. No.71) They are coming just after Lanthanum so they are known as Lanthanoids.

52. Electronic Configuration and Radii of Lanthanoids

53. Lanthanoid Contraction Lanthanoid contraction : In Lanthanoid series, with increasing atomic number, there is progressive decrease in atomic/ionic radii due to poor shielding effect of 4f-orbitals. Reason : Due to addition of new electrons into (n-2) f - subshell which shows more poor shielding effect. Consequences : Their separation is difficult as they have small difference in size. Basic strength of hydroxide decreases from left to right. ( La(OH) 3 is more basic than Lu(OH) 3 ) 4 d and 5 d transition series have almost same atomic radii. ( Zr and Hf have similar properties due to similar size)

54. Trend in ionic radii of lanthanoids

55. Physical properties of Lanthanoids The lanthanoids are highly dense metals. They have high melting points. They form alloys easily with other metals. They are soft, malleable and ductile with low tensile strength.

56. Properties of lanthanoids

57. Chemical reactions of Lanthanoids

58. Uses of lanthanoids Used in mischmetal an alloy of a lanthanoid ( 95%) with iron ( 5%) and traces of S, C, Ca & Al. It is used to make tracer bells, shells and lighter flints.

59. Actinoids The actinoids include the fourteen elements from Th(at.no.90) to Lr (at.no.103) The actinoids are radioactive elements. The earlier members have relatively long half-lives, latter ones have half life values ranging from a day to 3 minutes for lawrencium (Z =103).

60. Variation in Electronic configuration and radii General electronic configuration 5f 1-14 6d 0-1 7s 2

61. Ionic radii and Oxidation state

62. Variation in Oxidation states

63. Properties of actinoids

64. Differences between Lanthanoids and Actinoids

65. Uses Uses of actinoids : Th is used in atomic reactor and treatment of cancer. U and Pu are used as fuel in nuclear reactor.

66. Summary Transition (d- block ) elements. Transition series. General electronic configuration. Trends of properties in series. General characteristics

67. General characteristics of d-Block elements: Formation of coloured ions. Formation of complex compound. Catalytic property. Formation of interstitial compounds. Alloy formation.

68. Potassium dichromate: Methods of preparation , Properties and Uses. Potassium permanganate: Methods of preparation , Properties and Uses. Structure of Permanganate and Dichromate ions.

69. General properties of inner transition elements. General electronic configuration. Lanthanoid and Actinoids contraction. Properties of lanthanoids and Actinoids Uses of Lanthanoids and Actinoids Differences between lanthanoids and Actinoids

70. Home Assignment Account for the following: Transition elements exhibit higher enthalpies of atomization. Transition metals show paramagnetic behaviour . Transition metal ions form complexs . Transition metals form interstitial compounds. Most of the transition metals form alloys. Transition element form generally coloured compounds Transition elements show variable oxidation state.

71. How Potassium dichromate is prepare from Chromite ore. Write the chemical reactions involved in the preparation of potassium permanganate. The chromates and dichromates are interconvertible in aqueous solution depending upon pH of solution. Give reactions. What is meant by ‘disproportionation of an oxidation state ? Give two example.

72. Give reasons for the following questions: Chemistry of all the lanthanoids are quite similar. Size of trivalent lanthanoid cations decreases with increase in the atomic number. It is difficult to separate lanthanoid elements in pure state. Ce 4+ in aqueous solution is a good oxidizing agent. Ce 3+ can be easily oxidized to Ce 4+ . d-block elements exhibit more oxidation states than f - block elements

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