Introduction to d-block elements 2022 PDF

Introduction of d- Block Elements d-Subshell  The boundary surface of the orbital is the region of space where is there is high (typically 90%) probability of finding the electron.  This boundary surface is what chemists draw to represent the shape of an orbi...

Introduction of d- Block Elements d-Subshell  The boundary surface of the orbital is the region of space where is there is high (typically 90%) probability of finding the electron.  This boundary surface is what chemists draw to represent the shape of an orbital.  The planes on which the angular wavefunction passes through zero is called angular nodes or nodal planes.  An electron will not be found anywhere on a nodal plane.  A nodal plane cuts through the nucleus and separates the regions of positive and negative sign of the wavefunction. Figure: Representations of a set of five degenerate d atomic orbitals.  d- Block Elements 21 22 23 24 25 26 27 28 29 30 First T.S. Sc Ti V Cr Mn Fe Co Ni Cu Zn 3d1 4s2 3d2 4s2 3d3 4s2 3d5 4s1 3d5 4s2 3d6 4s2 3d7 4s2 3d8 4s2 3d10 4s1 3d10 4s2 39 40 41 42 43 44 45 46 47 48 Second T.S. Y Zr Nb Mo Tc Ru Rh Pd Ag Cd 4d1 5s2 4d2 5s2 4d4 5s1 4d5 5s1 4d5 5s2 4d7 5s1 4d8 5s1 4d10 5s0 4d 5s 4d10 5s2 10 1 57 72 73 74 75 76 77 78 79 80 Third T.S. Ta La* Hf W Re Os Ir Pt Au Hg 5d1 6s2 4f14 5d2 6s2 5d3 6s2 5d4 6s2 5d5 6s2 5d6 6s2 5d76s2 5d9 6s1 5d10 6s1 5d10 6s2 Fourth T.S. 89 104 105 106 107 108 109 110 111 112 Ac** Rf Db Sg Bh Hs Mt Ds Rg Cn 6d1 7s2  Three series of elements formed by filling of 3d, 4d and 5d subshells of electrons. Together these comprise the d-block elements.  Also called as transition elements because their position in the periodic table is between the s-block and p-block elements.  The two terms d-block metal and transition metal are often used interchangeably; however, they do not mean the same thing.  d-Block Elements vs Transition Elements  The name transition metal originally derived from the fact that their chemical properties were transitional between those of the s and p-blocks.  IUPAC definition of Transition Element: Element that has an incomplete d-subshell in either the neutral atom or its ions. d- Block Element 3d1 4s2 Sc Transition Element 3d2 Ti 4s2 V 3d3 4s2 Cr 3d55 4s 2 3d 4s1 Mn 3d6 4s2 Fe  What about Cu? d- Block Element Transition Element 3d 7 4s2 Co 3d8 4s2 Ni 3d9 4s2 Electronic Configuration Cu 3d10 4s1 Cu 3d10 4s0 Incompletely filled d-orbitals Cu+ available in ionicarestate hence 3d9 4s0 qualified as transition element. Cu2+ 3d8 4s0 Cu3+  Status of Ag and Au4d10 5s1 Ag 4d10 5s0 Ag+ 4d9 5s0 Qualified as Transition Ag2+ Element 4d8 5s0 Ag3+ 5d10 6s1 Au 5d10 6s0 Au+ 5d8 5s0 Qualified as Transition Element Au3+ 5d6 5s0 Au5+  What about Zn, Cd and Hg? 4s2 d- Block Element Transition Element 3d10 Zn 3d10 4s0 Zn2+ Rejected as 4d10 5s2 Transition Cd Element 4d10 5s0 Cd2+ 5d10 6s2 Hg 5d10 6s0 Qualified as Hg2+ Transition Element 5d8 6s0 Hg4+  Thus, two of the Group 12 elements (Zn, Cd) are members of the d block but are not transition elements as they do not have any compounds with an incomplete d subshell.  The situation for the third Group 12 element, mercury, is different: the report of a mercury(IV) compound (HgF4), which has the d8 electron configuration, qualifies mercury as a transition metal.  General Properties of Transition Elements  Electronic Configurations  Atomic Radii  Ionic Radii  Metallic Character and Related Properties  Enthalpy of Atomisation (∆Hº a)  Melting and Boiling Points  Atomic Volumes and Densities  Ionization Energies  Enthalpy of Hydration (∆Hhyd)  Standard Oxidation Potential Values and Reducing Properties of Transition Elements in Aqueous Solution  Variable Oxidation States  Catalytic Properties  Colour of Transition Metal Complex Ions  Magnetic Properties of Transition Metal Complexes  Electronegativity  Complex Formation Property  Alloy Formation  Formation of Interstitial Compounds  General Electronic Configuration of Transition Elements General Electronic Configuration of First Transition Series: [Ar]18 3d1-10 4s1-2 V.S.C. Sc Ti V Cr* Mn Fe Co Ni Cu** Zn 3d1-10 1 2 3 5 5 6 7 8 10 10 4s1,2 2 2 2 1 2 2 2 1 2 Extra stability 2 Extra stability of half filled of fully filled d-subshell d-subshell General Electronic Configuration of Second Transition Series: [Kr]36 4d1-10 5s0-2 V.S.C. Y Zr Nb* Mo* Tc Ru* Rh* Pd* Ag** Zn 4d1-10 1 2 4 5 5 7 8 10 10 10 5s0-2 2 2 1 1 2 1 1 0 1 2 Extra stability Extra stability of half filled of fully filled d-subshell Due interactions to Nuclear-electron d-subshell  General Electronic Configuration of Transition Elements General Electronic Configuration of Third Transition Series: [Xe]54 4f14 5d2-10 6s1-2 V.S.C. La** Hf Ta W* Re Os Ir* Pt* Au Hg 5d2-10 1 2 3 4 5 6 7 9 10 10 6s0-2 2 2 2 2 2 2 2 1 1 2 Extra stability * Due to Nuclear-electron and Electron-electron interactions. of fully filled d-subshell ** By definition La is a d-block element. However its physical and chemical properties resembles the lanthanide series elements which follows it. Therefore, La is considered as a member of the lanthanide series and is studied along with them. General Electronic Configuration of Third Transition Series: for Rf104 to Cn112 [Rn]86 5f14 6d2-10 7s1,2 for Ac89 [Rn]86 5f0 6d1 7s2 V.S.C. Ac** Rf Db Sg* Bh Hs Mt Ds Rg Cn 5d2-10 1 2 3 4 5 6 7 8 10 10 6s0-2 2 2 2 2 2 2 2 2 1 2  Atomic Radii Variation of Atomic Radii in a Given Period (Angstrom): Sc Ti V Cr Mn Fe Co Ni Cu Zn First T.S. (1.62) (1.47) (1.34) (1.27) (1.26) (1.26) (1.25) (1.24) (1.28) (1.38) Y Zr Nb Mo Tc Ru Rh Pd Ag Cd Second T.S. (1.80) (1.60) (1.46) (1.39) (1.36) (1.34) (1.34) (1.37) (1.44) (1.54 ) Third T.S. La Hf Ta W Re Os Ir Pt Au Hg (1.87) (1.58) (1.46) (1.39) (1.37) (1.35) (1.36) (1.38) (1.44) (1.57) (i) The atomic radii of the transition metals lie in between those of s- and p-block elements. (ii) Generally the atomic radii of d-block elements in a series decrease with an increase in atomic number but the decrease in atomic size is small after midway. (iii) At the end of the period, there is a slight increase in the atomic radii. (iv) There is no major change in atomic radii going from Fe to Cu. At the beginning: Attractive forces > Repulsive forces From Fe to Cu: Attractive forces = Repulsive forces At the end: Attractive force < Repulsive force Variation of Atomic Radii in a Given Group: Sc, Y, and La increases. Rest others have almost identical radii due to lanthanide contraction.  Shielding/screening effect describes the decrease in attraction between an electron and the nucleus in any atom with more than one electron shell Atomic and Ionic Size The atomic and ionic radii of the transition elements decrease from group 3 to group 6 due to the poor shielding offered by the small number of d-electrons. Those placed between groups 7 and 10 have somewhat similar atomic radii and those placed in groups 11 and 12 have larger radii. Lanthanide contraction describe the decrease in ionic radii of the elements, is the greater-than-expected decrease in atomic radii/ ionic radii of the elements in the lanthanide series from atomic number 57, lanthanum, to 71, lutetium, which results in smaller than otherwise expected atomic radii/ionic radii for the subsequent elements starting with 72, hafnium Note: Atomic, ionic, covalent radius Size of atom controls the properties Lanthanide Contraction: 1. Covalent and ionic radii normally increase on descending a group in the periodic table due to the presence of extra-filled shells of electrons. 2. On moving from left to right across a period, the covalent and ionic radii decrease because the extra orbital electrons incompletely shield the extranuclear charge. Thus, all electrons are pulled in closer. 3. The shielding effect of electrons decreases in the order s>p>d>f. 4. Lanthanide contraction in size from Ce to Lu is fairly small (about 0.2 AO).  Ionic Radii Same metal ion in different oxidation states: e.g. Ti2+ > Ti3+ ; Cr2+ > Cr3+ > Cr4+ > Cr5+ > Cr6+ ; Cu+ > Cu2+ Ionic radii of the cations of different element in the same oxidation state e.g. Ti2+ > V2+ > Cr2+ > Mn2+ > Fe2+ > Co2+ > Ni2+ > Cu2+ For group 3 cations: Sc3+ < Y3+ < La3+ Metallic Character  All the transition elements show metallic character  Good conductor of electricity and heat  Hard and brittle  Crystal structure: bcc, hcp, ccp or fcc  3. Density All TE have densities > 5 g/cm Exceptions: Sc, Y, Ti 1000 °C 5. Ionization Energy There is little change in the first ionization energy of transition elements from Sc to Cu. This is because : a) the atomic radii remains almost constant. TE can form either ionic or covalent bonds 6. Colour (due to d-d transition) Colour depends on: Ligand type No. of ligands Geometry of complex Example: [Ni(NH3)6]2+ (blue) [Ni(H2O)6]2+ (green) MW [Ni(NO2)6]2+ (brown)  Empty or Completely Filled d-orbitals Colourless due to (No d-d transition) e.g. ZnSO4 and TiO2 1- Transition metals (d-block elements): “Other  The colour due to d –d transition, charge transfer or crysal defect. causes of colour”  Absorption bands are wide because d orbitals are affected by the environmental factors such as the nature and number of ligands. 2-Charge transfer e.g. MnO4- (deep violet) Abs. OR Wave length 3-Defect in crystal lattice 7. Magnetic Properties Many transition metal ionic compounds are paramagnetic because the metal ion has one or more unpaired electrons.0 Transition metal ions with a d or d10 configuration or with all electrons paired are diamagnetic. Magnetic moment (µ) µs = √n(n+2) Units (B.M.) Gouy Method Ferro/Ferri/Antiferro magnetism The iron triad (Fe,Co & Ni) exhibits ferromagnetism which is a much stronger magnetic effect than paramagnetism. A ferromagnetic solid consists of regions called domains in which atoms have their magnetic moments aligned. When placed in a magnetic field, all the domains are aligned and the solid becomes magnetized.  8. Catalytic Activity TMs and their compounds are important catalysts 9. Complex Formation All TE can form complexes Complex: Metal ion + ligand OR Lewis acid + Lewis base 10. Nonstoichiometry Compounds of indefinite structure and proportion e.g. FeO (Fe0.84-0.94O) 11. Abundance Fe 4th, Ti 9th and Mn 12th 1st row more abundunt (Tc) Technetium: man made Ag, Au, Cd, Hg: very rare Catalytic Activity Transition metals and their compounds are often good catalysts. Transition metals and their compounds function as catalysts either because of their ability to change oxidation state or, in the case of the metals, to adsorb other substances onto their surface and activate them in the process. Iron in the Haber Process The Haber Process combines hydrogen and nitrogen to make ammonia using an iron catalyst. Nickel in the hydrogenation of C=C bonds This reaction is at the heart of the manufacture of margarine from vegetable oils. However, the simplest example is the reaction between ethene and hydrogen in the presence of a nickel catalyst. Transition metal compounds as catalysts Vanadium(V) oxide in the Contact Process The Contact Process is a reaction that converts Sulfur dioxide into Sulfur trioxide. Sulfur dioxide gas is passed together with air (as a source of oxygen) over solid vanadium(V) oxide catalyst. Iron ions in the reaction between persulfate ions and iodide ions Persulphate ions (peroxodisulphate ions), S2O82-, are very powerful oxidizing agents. Iodide ions are very easily oxidized to iodine. And yet the reaction between them in solution in water is very slow. The reaction is catalyzed by the presence of either iron(II) or iron(III) ions. S2O8−2+2I−→2SO2−4+I2  12. Oxidation states of first-row d- block ions: The most stable oxidation states are in red, rarer oxidation states green: 3 4 5 6 7 8 9 10 11 1 Sc 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 3 4 4 4 4 4 4 4 4 The higher 5 5 5 5 oxidation states become less These achieve 6 6 6 stable as the divalent state the group oxidation state 7 becomes dominant Maximum at Mn(VII)  Physical Properties It is useful, in the beginning, to identify the physical and chemical properties of transition elements that differ from main group elements (s-block) such as Calcium. Transition elements: have large charge/radius ratio; are hard and have high densities; have high melting and boiling points; form compounds that are often paramagnetic; show variable oxidation states; form colored ions and compounds; form compounds with profound catalytic activity; form stable complexes.