D and F block

• Elements from 3rd group to 12th group in the Modern Periodic table are called d-block elements
• Last electron enters the penultimate d-subshell
• Placed between s-block and p-block elements
• Transition elements show a regular transition from highly electropositive metals of s-block to less electropositive p-block elements
• Transition elements contain partially filled d orbitals in their atomic state or in any of their oxidation state
• Zinc, Cadmium, and Mercury contain completely filled d-orbitals and are not considered transition elements
• Four series of transition elements:

  • 3d series: Scandium (Sc) to Zinc (Zn)
  • 4d series: Yttrium (Y) to Cadmium (Cd)
  • 5d series: Lanthanum (La) to Mercury (Hg)
  • 6d series: Actinium (Ac) to Copernicium (Cp)
• General outer electronic configuration of d-block elements is (n-1)d1-10 ns1-2
• In some cases, ns electrons are transferred to (n-1)d level
• Exceptions in electronic configurations of Cr and Cu in the 3d series due to extra stability of half-filled (d5) and completely-filled (d10) configurations
• Electronic configurations of Zn, Cd, and Hg are (n-1)d10 ns2
• First row transition series elements' electronic configurations:

  • Scandium (Sc): [Ar] 3d1 4s2
  • Titanium (Ti): [Ar] 3d2 4s2
  • Vanadium (V): [Ar] 3d3 4s2
  • Chromium (Cr): [Ar] 3d4 4s2
  • Manganese (Mn): [Ar] 3d5 4s1
  • Iron (Fe): [Ar] 3d6 4s2
  • Cobalt (Co): [Ar] 3d7 4s2
  • Nickel (Ni): [Ar] 3d8 4s2
  • Copper (Cu): [Ar] 3d10 4s1
  • Zinc (Zn): [Ar] 3d10 4s2
• Atomic and ionic radii of transition elements:

  • Initially decrease, then become constant, and increase towards the end of the series
  • Lanthanide contraction affects the radii of 2nd and 3rd row transition metals
• Melting and boiling points of transition elements:

  • Generally hard with high melting and boiling points
  • Melting and boiling points increase up to the middle and then decrease in a transition series
• Ionisation enthalpy of transition elements:

  • Generally increases from left to right
  • After removal of one electron, relative energies of 4s and 3d orbitals change, affecting ionisation enthalpy
• Oxidation states of transition elements:

  • Show variable oxidation states due to comparable energies of d and s electrons
  • Maximum oxidation state increases up to the middle and then decreases in a transition series
• Electrode potential of transition elements:

  • Generally increases from left to right with some exceptions
  • Copper does not easily react with acid and liberate H2 due to its electrode potential
• The standard reduction potential (E0) for zinc (Zn) is high due to its stable electronic configuration
• The E0 (Mn3+ | Mn2+) is high because of the stable half-filled configuration of Mn2+
• The E0 (Fe2+ | Fe3+) is low because after the removal of one electron from Fe2+, it achieves a stable electronic configuration
• Cu2+ is more stable than Cu+ in aqueous solution due to the greater negative hydration enthalpy of Cu2+ compared to Cu+
• Transition metals exhibit paramagnetism and diamagnetism, with some showing ferromagnetism which is an extreme case of paramagnetism
• Paramagnetism arises from the presence of unpaired electrons, each associated with a spin magnetic moment and an orbital magnetic moment
• For compounds of 1st-row transition elements, only the spin magnetic moment is considered, determined by the number of unpaired electrons
• Most transition metal ions or compounds are colored due to the presence of partially filled d orbitals
• When an electron is excited from a lower energy d orbital to a higher d level, it absorbs energy and emits a color in the visible region
• Transition metals form a large number of complexes due to their comparatively smaller size, high ionic charge, presence of partially filled d orbitals, and ability to show variable oxidation states
• Transition metals act as catalysts in many chemical reactions due to their large surface area and ability to show variable oxidation states
• Interstitial compounds are formed when smaller atoms like H, N, C, B are trapped inside the crystal lattice of the metal, they are non-stoichiometric and retain metallic conductivity
• Alloys are homogeneous solid solutions of elements where at least one element is a metal, formed by atoms with metallic radii within about 15% of each other
• Alloys formed by transition metals are hard and have high melting points
• Potassium dichromate (K2Cr2O7) is prepared from chromite ore and is a strong oxidizing agent
• Potassium dichromate is used as a primary standard in volumetric analysis and in various reactions
• Potassium permanganate (KMnO4) is commercially prepared from MnO2 and is a good oxidizing agent in acidic, basic, and neutral media
• Potassium permanganate forms dark purple crystals and decomposes when heated to liberate O2
• The oxidizing property of KMnO4 is due to the reaction: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
• Potassium permanganate solution oxidises:
• Oxalates to carbon dioxide:

  • 5 C2O42- → 2 CO2 + 2e–
  • 2 MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
  • 5 C2O42- + 2 MnO4- + 16H+ → 10 CO2 + 2 Mn2+ + 8H2O
• Iron(II) to iron(III):

  • 5 Fe2+ → 5 Fe3+ + 5e–
  • MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
  • 5 Fe2+ + MnO4- + 8H+ → 5 Fe3+ + Mn2+ + 4H2O
• Nitrites to nitrates:

  • 5 NO2– + 5H2O → 5 NO3- + 10H+ + 10e–
  • 2 MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
  • 5 NO2– + 2 MnO4- + 6H+ → 5 NO3- + 2 Mn2+ + 3H2O