1 / 57

The d- Block Elements

The d- Block Elements. By : A P Singh. Definition of d-block elements. d-block elements: The elements of periodic table belonging to group 3 to 12 are known as d-Block elements . because in these elements last electron enters in d sub shell or d orbital .

serena
Download Presentation

The d- Block Elements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The d- Block Elements By : A P Singh

  2. Definition of d-block elements • d-block elements:The elements of periodic table belonging to group 3 to 12 are known as d-Block elements. because in these elements last electron enters in d sub shell or d orbital . • The d -block elements lies in between s- and p-block elements in the long form of periodic table

  3. Transition Elements A transition element is defined as the one which has incompletely filled d orbitals in its ground state or in any one of its oxidation states. i.e. A transition element should have partially filled (n-1) d orbital.

  4. Group 7 Presentation

  5. How are d - Block Elements & Transition elements different? All d block elements are not transition elements but all transition elements are d-block elements All d block elements are not transition elements because d block elements like Zinc have full d10 configuration in their ground state as well as in their common oxidation state.which is not according to definition of transition elements.

  6. Which of the d-block elements may not be regarded as the transition elements? • WhyZn, Cd and Hg are not considered as transition elements. • Why Scandium is a transition element but Zinc is not. • Copper atom has completely filled d orbital (3d10) in its ground state, yet it is transition element. Why • Silver atom has completely filled d orbital (4d10) in its ground state, yet it is transition element. Why • Why the very name ‘transition’ given to the elements of d-block .

  7. Answers • Zn, Cd and Hg • Because they do not have vacant d-orbitals neither in the atomic state nor in any stable oxidation state. • Scandium is a transition because it has incompletely filled d orbitals in its ground state but Zinc have full d10 configuration in their ground state as well as in their common oxidation state • Copper (Z = 29) can exhibit +2 oxidation state wherein it will have incompletely filled d-orbitals (3d), hence a transition element. • Silver (Z = 47) can exhibit +2 oxidation state wherein it will have incompletely filled d-orbitals (4d), hence a transition element. • The very name ‘transition’ given to the elements of d-block is only because of their position between s– and p– block elements.

  8. General & physical Properties of d-Block Elements physical properties Atomic & Ionic size Ionization Enthalpy Oxidation States of d-Block Elements Coloured Ions Catalytic properties Magnetic properties Formation of Complex Compounds Formation of Interstitial Compounds

  9. PHYSICAL PROPERTIES

  10. melting and boiling points are high. A large number of unpaired electrons take part in bonding so they have very strong metallic bonds and hence high m.pt & b.pt MELTING AND BOILING POINTS (ENTHALPIES OF ATOMISATION) :

  11. They have high enthalpies of atomisation . The maxima is at about the middle of each series. A large number of unpaired electrons take part in bonding so they have very strong metallic bonds and hence high enthalpy of atomization.

  12. Atomic & Ionic size

  13. Along the rows nuclear charge increases but the penultimate d-sub shell has poor shielding effect so atomic and ionic size remain almost same . • The radii of the third (5d) series are virtually the same as those of the corresponding members of the second series.

  14. This phenomenon is associated with the intervention of the 4forbital, the filling of 4f before 5d orbital results in a regular decrease in atomic radii called Lanthanoid contraction which essentially compensates for the expected increase in atomic size with increasing atomic number. • The net resultof the lanthanoid contraction is that the second and the third d series exhibit similar radii (e.g., Zr 160 pm, Hf 159 pm)

  15. Ionization Enthalpies IE2 :V < Cr > Mn and Ni < Cu > Zn IE3 : Fe << Mn

  16. Due to an increase in nuclear charge which accompanies the filling of the inner d- orbitals , There is an increase in ionization enthalpy along each series of the transition elements from left to right. • However, many small variations occur.

  17. oxidation states • Transition elements have variable oxidation states ,due to very small energy difference between (n-1)d & ns sub-shell electrons from both the sub-shell take part in bonding

  18. The elements which give the greatest number of oxidation states occur in or near the middle of the series. Manganese, for example, exhibits all the oxidation states from +2 to +7. • Low oxidation states are found when a complex compound has ligands capable of π-acceptor character in addition to the σ-bonding. • For example, in Ni(CO)4 and Fe(CO)5, the oxidation state of nickel and iron is zero.

  19. Trends in the M2+/M Standard Electrode Potentials

  20. COLOURED IONS Most of the transition metal compounds (ionic as well as covalent) are coloured both in solid state & in aqueous state. Generally the elements/ions having unpaired electrons produce coloured compound.

  21. Zinc sulfate Hepta- hydrate Nickel(II) nitrate hexa- hydrate Titanium oxide sodium chromate Potassium ferricyanide Vanadyl Sulphate dihydrate Mangnaese(II) chloride tetrahydrate Scandium oxide Cobalt(II) chloride Copper(II) sulfate penta- hydrate

  22. Splitting of d-orbital energies by an octahedral field of ligands

  23. ES ES eg eg hv GS GS Do t2g t2g complex in electronic excited state (ES) complex in electronic Ground State (GS) d-d transition

  24. An artist’s wheel

  25. Questions: Q1.Of the ions Ag+, Co2+ & Ti4+ which one will be coloured in aqueous soln. ? Q2. Why hydrated copper sulphate is blue while anhydrous copper sulphate is white? Q3.[Ti(H2O)6]3+ is coloured while [Sc(H2O)6]3+ is colourless . Explain? Q4. Why transtion metals & their compounds act as good catalyst? Q5. Why transtion metals generally forms colouredcompounds

  26. CATALYTIC PROPERTIES • Vanadium(V) oxide,V2O5 (in Contact Process) • Finely divided iron (in Haber’s Process) • Nickel (in Catalytic Hydrogenation) • Cobalt (Synthesis of gasoline) • This property is due to- • Presence of unpaired electrons in their incomplete d orbitals. • Variable oxidation state of transition metals. • In most cases , provide large surface area with free valencies.

  27. For example • iron(III) catalyses the reaction between iodide and per sulphate ions Explanation

  28. Magnetic properties • When a magnetic field is applied to substances, mainly two types of magnetic behaviour are observed: diamagnetism and paramagnetism. • Diamagnetic substances are repelled by the applied field while the paramagnetic substances are attracted. • Substances which are attracted very strongly are said to be ferromagnetic. • In fact, ferromagnetism is an extreme form of paramagnetism.

  29. Most of the transition elements and their compounds show paramagnetism. • Paramagnetism arises from the presence of unpaired electrons, each such electron have a magnetic moment. • The magnetic moment of any transition element or its compound/ion is given by (assuming no contribution from the orbital magnetic moment). • μs  = √n(n+2) BM • Here n is the number of unpaired electrons

  30. The paramagnetism first increases in any transition element series, and then decreases. The maximum paramagnetism is seen around the middle of the series.

  31. Questions- • Q. 1: Which ion has maximum magnetic moment   (a) V3+                                   (b) Mn3+   (c) Fe3+                                 (d) Cu2+ • Ans: c • Q.2. What is the magnetic moment of Mn2+ ion (Z= 25) in aqueous solution ? • Ans.- With atomic number 25, the divalent Mn2+ ion in aqueous solution will have d5 configuration (five unpaired electrons).Hence, The magnetic moment, μ is • μ = √5(5 + 2) = 5.92BM

  32. Formation of Complex Compounds • Complex compounds are those in which the metal ions bind a number of anions or neutral molecules giving complex species with characteristic properties. • The transition metals form a large number of complex compounds. • A few examples are: [Fe(CN)6]3–, [Fe(CN)6]4–, [Cu(NH3)4]2+ and [PtCl4]2–.

  33. This property is due to the- • comparatively smaller sizes of the metal ions • their high ionic charges and the • availability of d orbitals for bond formation.

  34. FORMATION OF INTERSTITIAL COMPOUNDS • The transition elements form a large number of interstitial compounds in which small atoms such as hydrogen, carbon, boron and nitrogen occupy the empty spaces in their lattices. • They are usually non stoichiometric and are neither typically ionic nor covalent, • for example, TiC, Mn4N, Fe3H, VH0.56 and TiH1.7, etc.

  35. C Fe

  36. The principal physical and chemical characteristics of these compounds are -: high melting points, higher than those of pure metals. very hard. retain metallic conductivity. chemically inert.

  37. Oxides and Oxoanions of Metals All the metals except scandium form MxOy oxides which are ionic. As the oxidation number of a metal increases, ionic character decreases. In higher oxides, the acidic character is predominant V2O2 < V2O4 < V2O5. Less basic more basic amphoteric

  38. Potassium dichromate K2Cr2O7 Preparation : Dichromates are generally prepared from chromate, which in turn are obtained by the fusion of chromite ore (FeCr2O4) with sodium or potassium carbonate in free access of air. 4 FeCr2O4 + 8 Na2CO3 + 7 O2 → 8 Na2CrO4 + 2 Fe2O3 + 8 CO2 2Na2CrO4 + 2 H+ → Na2Cr2O7 + 2 Na+ + H2O Na2Cr2O7 + 2 KCl → K2Cr2O7 + 2 NaCl

  39. Structure : The chromate ion is tetrahedral whereas the dichromate ion consists of two tetrahedra sharing one corner with Cr–O–Cr bond angle of 126°.

  40. Properties Oxidising Properties In acidic solution,its oxidising action can be represented as follows: Cr2O72– + 14H+ + 6e– → 2Cr3+ + 7H2O ; e.g. • a) 6 I–→ 3I2 + 6 e– c) 3 Sn2+ → 3Sn4+ + 6 e– • b) 3 H2S → 6H+ + 3S + 6e– d) 6 Fe2+ → 6Fe3+ + 6 e–

  41. Potassium Permanganate, KMnO4 Preparation : • prepared by fusion of MnO2 with an alkali metal hydroxide • and an oxidising agent(O2 or KNO3) this produces the dark green K2MnO4 which disproportionates in a neutral or acidic solution to give permanganate. 2MnO2 + 4KOH + O2 → 2K2MnO4 + 2H2O 3MnO42– + 4H+ → 2MnO4–+ MnO2 + 2H2O • In the laboratory, a manganese (II) ion salt is oxidised by • peroxodisulphate to permanganate. • 2Mn2+ + 5S2O82– + 8H2O → 2MnO4– + 10SO42– + 16H+

  42. Properties Oxidising Properties : Strong oxidising agent in acidic as well as in neutral & basic medium :

More Related