D and F block

• D block elements tend to form stable 2 oxidation states by losing two electrons and gaining stability through noble gas configuration.
• The d-block of the periodic table contains elements of groups 3-12 where d orbitals are progressively filled in each of the four long periods
• The f-block consists of elements where 4f and 5f orbitals are progressively filled, placed in a separate panel at the bottom of the periodic table
• Transition metals and inner transition metals refer to elements of d-block and f-block respectively
• There are four series of transition metals: 3d series (Sc to Zn), 4d series (Y to Cd), 5d series (La and Hf to Hg), and 6d series (Ac and elements from Rf to Cn)
• The two series of inner transition metals are 4f (Ce to Lu) and 5f (Th to Lr) known as lanthanoids and actinoids respectively
• 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, hence 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 exhibit properties like a variety of oxidation states, formation of colored ions, complex formation with ligands, catalytic property, and paramagnetic behavior
• Transition elements have greater similarities in properties within a horizontal row compared to non-transition elements, but some group similarities also exist
• 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 because it has completely filled d orbitals (3d10) in its ground state and oxidized state
• Transition Elements Exam
• Transition elements have high enthalpies of atomisation due to a large number of unpaired electrons in their atoms, resulting in stronger interatomic interaction and bonding between atoms
• Greater number of valence electrons leads to stronger bonding
• Metals with high enthalpy of atomisation tend to be noble in their reactions
• Metals of the second and third series have greater enthalpies of atomisation than the corresponding elements of the first series
• Ions of the same charge in a series show a progressive decrease in radius with increasing atomic number
• Atomic radii decrease within a series due to the net electrostatic attraction between the nuclear charge and the outermost electron
• The lanthanoid contraction is associated with the filling of 4f orbitals before the 5d series begins
• Lanthanoid contraction results in a decrease in atomic radii of the 5d series compared to the 4d series
• The shielding effect of a d electron is less effective than that of an f electron, leading to a decrease in metallic radius
• Increase in atomic mass results in a general increase in the density of transition elements
• Zinc has a low value as the ionisation causes the removal of one 4s electron, resulting in the formation of a stable d10 configuration
• The third ionisation enthalpies show the greater difficulty of removing an electron from the d5 (Mn 2+) and d10 (Zn 2+) ions
• The third ionisation enthalpies are generally quite high
• Transition elements exhibit a great variety of oxidation states in their compounds
• Manganese exhibits all oxidation states from +2 to +7
• Scandium (Z = 21) does not exhibit variable oxidation states
• The highest oxidation states of reasonable stability correspond to the sum of the s and d electrons up to manganese
• The variability of oxidation states in transition elements arises from incomplete filling of d orbitals, with oxidation states differing by unity
• In the d-block, lower oxidation states are favored by heavier members, unlike in the p-block
• The highest oxidation numbers are achieved in TiX4, VF5, and CrF6
• The stability of Cu2+ (aq) over Cu+ (aq) is due to the much more negative ∆hydHV of Cu2+ (aq) than Cu+, compensating for the second ionisation enthalpy of Cu
• The highest oxidation number in the oxides coincides with the group number and is attained in Sc2O3 to Mn2O7
• Oxygen can stabilize high oxidation states in oxides and oxocations, exceeding the ability of fluorine
• The ability of oxygen to form multiple bonds to metals explains its superiority in stabilizing high oxidation states
• Explanation for irregular variation of ionisation enthalpies (first and second) in the first series of transition elements:

  • The irregular variation of ionisation enthalpies can be explained by the irregular variation of the sublimation enthalpies, which are relatively much less for manganese and vanadium
• Reason for increasing oxidising power in the series VO2+ < Cr2O72- < MnO4-:

  • The increasing oxidising power is due to the increasing stability of the lower species to which they are reduced
• Explanation for the irregularity in Eo values for first row transition metals:

  • The irregularity in Eo values can be explained by the irregular variation of ionisation enthalpies (ΔiH) and sublimation enthalpies, which are relatively much less for manganese and vanadium