The d-and f-Block Elements

• The d-block of the periodic table contains elements from groups 3-12 where d orbitals are progressively filled in each of the four long periods
• The f-block consists of elements where 4 f and 5 f orbitals are progressively filled, placed in a separate panel at the bottom of the periodic table
• Transition metals and inner transition metals refer to the elements of the d- and f-blocks respectively
• Mainly four series of transition metals:

  • 3d series (Sc to Zn)
  • 4d series (Y to Cd)
  • 5d series (La and Hf to Hg)
  • 6d series (Ac and elements from Rf to Cn)
• Two series of inner transition metals:

  • 4f (Ce to Lu) known as lanthanoids
  • 5f (Th to Lr) known as actinoids
• Transition metals are defined as metals with incomplete d subshell either in neutral atom or in their ions
• Zinc, cadmium, and mercury of group 12 have full d10 configuration in their ground state and common oxidation states, not regarded as transition metals
• Transition elements have partly filled d or f orbitals in their atoms, making them different from non-transition elements
• Transition elements and their compounds are studied separately from non-transition elements
• Transition elements exhibit catalytic property, paramagnetic behavior, and form colored ions
• Greater similarities exist in properties of transition elements of a horizontal row compared to non-transition elements
• Transition elements of a horizontal row exhibit certain characteristic properties due to partly filled d orbitals
• Scandium (Z = 21) is a transition element due to incompletely filled 3d orbitals in its ground state, while zinc (Z = 30) is not a transition element as it has completely filled d orbitals in its ground state and oxidized state
• In single-celled organisms, substances can easily enter the cell due to a short distance, while in multicellular organisms, the distance is larger because of a higher surface area to volume ratio
• Multicellular organisms require specialised exchange surfaces for efficient gas exchange of carbon dioxide and oxygen due to their higher surface area to volume ratio
• Zinc atoms have completely filled d orbitals (3d10) in both their ground state and oxidised state, which is why they are not considered transition elements
• Transition elements exhibit typical metallic properties such as high tensile strength, ductility, malleability, high thermal and electrical conductivity, and metallic lustre
• Most transition elements have one or more typical metallic structures at normal temperatures, except for Zn, Cd, Hg, and Mn
• Transition metals (excluding Zn, Cd, and Hg) are hard, have low volatility, and high melting and boiling points
• The high melting points of transition metals are attributed to the involvement of a greater number of electrons from (n-1)d in addition to the ns electrons in interatomic metallic bonding
• The lanthanoid contraction results in the second and third d series exhibiting similar radii and very similar physical and chemical properties
• Transition elements exhibit higher enthalpies of atomisation due to the large number of unpaired electrons in their atoms, leading to stronger interatomic interaction and bonding
• Transition elements have high enthalpies of atomisation, with maxima at about the middle of each series, indicating one unpaired electron per d orbital is particularly favorable for strong interatomic interaction
• There is an increase in ionisation enthalpy along each series of transition elements from left to right due to an increase in nuclear charge
• Ionisation enthalpy increases along each series of transition elements from left to right due to an increase in nuclear charge accompanying the filling of inner d orbitals
• The first three ionisation enthalpies of the first series of transition elements do not increase as steeply as in non-transition elements
• The variation in ionisation enthalpy along a series of transition elements is much less compared to non-transition elements
• In the 3d series, the trend of increasing ionisation enthalpy breaks for the formation of Mn2+ and Fe3+ ions, both having d5 configuration
• The lowest common oxidation state of transition metals is +2, with the sum of the first and second ionisation enthalpies required to form M2+ ions
• The third ionisation enthalpies of transition elements show the greater difficulty of removing an electron from d5 (Mn2+) and d10 (Zn2+) ions
• Transition elements exhibit a great variety of oxidation states in their compounds, with manganese showing all oxidation states from +2 to +7
• The variability of oxidation states in transition elements arises from incomplete filling of d orbitals, leading to oxidation states differing by unity
• In the d-block elements, lower oxidation states are favored by heavier members, unlike in p-block elements where lower oxidation states are favored by the heavier members
• Low oxidation states are found in complex compounds with ligands capable of p-acceptor character in addition to s-bonding
• Table 4.4 contains thermochemical parameters related to the transformation of solid metal atoms to M2+ ions in solution and their standard electrode potentials
• Observed values of EV and those calculated using the data of Table 4.4 are compared in Fig. 4.4
• Cu has a positive EV, which accounts for its inability to liberate H2 from acids
• Only oxidising acids (nitric and hot concentrated sulphuric) react with Cu, with the acids being reduced
• The high energy to transform Cu(s) to Cu2+(aq) is not balanced by its hydration enthalpy
• The general trend towards less negative EV values across the series is related to the increase in the sum of the first and second ionisation enthalpies