D & F Block Elements

• d block elements are found from the third group to the twelfth group of the modern periodic table
• d block elements are also known as transition elements or transition metals
• Transition elements have at least one unpaired electron in their d orbital in atomic or any oxidation state
• All transition elements are d-block elements, but not all d-block elements are transition elements
• Transition elements exhibit variable oxidation states due to the involvement of (ns) and (n-1)d electrons in bonding
• Transition metals show colour properties due to the presence of unpaired electrons in their d orbitals
• Most transition metal ions are paramagnetic due to the presence of unpaired electrons in their d orbitals
• Transition elements exhibit catalytic properties because of their variable valency and free valencies on their surfaces
• Transition elements are in a powdered state due to the greater surface area, which aids in catalytic properties
• Transition metals and their compounds exhibit catalytic properties in various processes
• Percentage of carbon in different types of iron:

  • Wrought iron: 0.1 to 0.25%
  • Steel: 0.25 to 2.0%
  • Cast iron: 2.6 to 4.3%
  • Pig iron: 3.5 to 4.6%
• Transition elements form interstitial compounds with elements like nitrogen, hydrogen, boron, etc.
• Non-stoichiometry in transition metal compounds of group 16 elements is due to variable valency

  • Non-stoichiometric compounds have indefinite proportions and structures
  • Caused by a defect in the solid structure
• f Block Elements:

  • Also known as inner transition elements
  • Electrons enter (n-2)f orbitals
  • Electronic configuration: (n-2)f(0−14)(n-1)d(0−1)ns2
• Lanthanides:

  • Chemically similar to lanthanum
  • Reactive elements not found in nature in the free state
  • Non-radioactive (except promethium)
  • Properties: good conductors of electricity and heat, soft metals, silvery-white color
• Actinides:

  • Elements with atomic numbers 89 to 103
  • Radioactive in nature
  • Properties: silvery appearance, exhibit oxidation states, highly reactive
• Difference between Lanthanides and Actinides:

  Lanthanides:

  • Non-radioactive except promethium

  Actinides:

  • All radioactive
• Similarities between Lanthanides and Actinides:

  • Fill (n-2) f subshell
  • Similar outermost electronic configurations
  • Similar properties: oxidation states, electropositivity, reactivity, magnetic properties
• Lanthanide Contraction:

  • Gradual decrease in atomic and ionic size of lanthanoids with increasing atomic number
  • Consequences: difficulty in separation, atomic size, electronegativity, effect on basic strength of hydroxides, ionization energy
• 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 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 d- and f-blocks 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 have incomplete d subshells either in neutral atoms or ions according to IUPAC
• Zinc, cadmium, and mercury of group 12 are not considered transition metals as they have full d10 configuration in their ground state and common oxidation states
• Transition elements have partly filled d or f orbitals, making them different from non-transition elements
• Transition elements exhibit properties like a variety of oxidation states, formation of colored ions, and complex formation with ligands due to partly filled d orbitals
• Transition metals and their compounds show catalytic property and paramagnetic behavior
• There are greater similarities in properties of transition elements within a horizontal row compared to non-transition elements
• The d-block occupies the middle section of the periodic table, flanked between s- and p-blocks
• The d-orbitals of transition elements protrude more than other orbitals, influencing and being influenced by the surroundings
• The electronic configurations of outer orbitals of transition elements are (n-1)d1-10ns1-2, with exceptions due to energy differences between d and ns orbitals
• Scandium is a transition element due to incompletely filled 3d orbitals, while zinc is not a transition element as it has completely filled d orbitals
• Transition elements exhibit higher enthalpies of atomisation due to the large number of unpaired electrons in their atoms, resulting in stronger interatomic interaction and bonding between atoms
• The transition elements show an increase in ionisation enthalpy along each series from left to right due to an increase in nuclear charge accompanying the filling of the inner d orbitals
• The first three ionisation enthalpies of the first series of transition elements show that the successive enthalpies of these 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 of transition metals, the irregular trend in the first ionisation enthalpy can be explained by the alteration of relative energies of 4s and 3d orbitals when one electron is removed
• When d-block elements form ions, ns electrons are lost before (n – 1) d electrons