Brief Introduction to D and F Blocks

Overview

This lecture focused on the revision of elements of the D and F blocks, discussing their major physical and chemical properties, electronic configuration, oxidation states, and their important compounds.

D Block (Transition Elements)

• In D block elements, the last electron enters the n-1 d subshell; these are called transition elements.
• The D block has four series: 3D (Sc-Zn), 4D (Y-Cd), 5D (La-Hg), 6D (Rf-Cn).
• Exception: Zn, Cd, Hg have completely filled d orbitals.
• Exceptions in electronic configuration: Cr (3d⁵ 4s¹), Cu (3d¹⁰ 4s¹).
• Physical properties: high tensile strength, ductility, malleability, high thermal/electrical conductivity; except Zn, Cd, Hg, Mn.
• Metallic bonding is strong due to unpaired d electrons, resulting in a high melting point.
• Oxidation states: greatest variety in the middle series; Mn (+2 to +7).
• Ionic radius: size decreases to the right in the series due to poor shielding effect; 4D and 5D sizes are almost the same (lanthanoid contraction).
• Paramagnetism: magnetic moment (μ = √n(n+2)) depends on the number of unpaired electrons.
• Colored compounds: show color due to d-d transitions.
• Catalytic properties: ability to have multiple oxidation states and intermediate compounds.
• Zn, Cd, Hg are very stable and generally do not release hydrogen.
• Cu is mostly stable in the 2+ state; Cu⁺ is not stable in water.

Important Compounds of D Block

• Potassium Dichromate (K₂Cr₂O₇): orange crystals, soluble in water, strong oxidizing agent.
• Potassium Permanganate (KMnO₄): dark purple color, strong oxidizing agent, produces different products under acidic/alkaline/neutral conditions.
• Both act as oxidizing agents, converting Fe²⁺ to Fe³⁺ and I⁻ to I₂.

F Block (Inner Transition Elements)

• The F block fills the 4F (Lanthanides: Ce-Lu) and 5F (Actinides: Th-Lr) subshells.
• Due to lanthanoid contraction, all lanthanides have very similar sizes, making separation difficult.
• Lanthanides mainly show +3 oxidation state, some also +2 and +4.
• Actinides mainly +3, but oxidation states from +4 to +7 are possible due to small ΔE (5f, 6d, 7s).
• Lanthanides form fewer complexes; actinides form more complexes.
• Actinides can form oxo-cations, lanthanides cannot.

Key Terms & Definitions

• D block elements — elements in which the last electron enters the n-1 d subshell.
• Transition elements — D block elements with incomplete d orbitals.
• Lanthanide contraction — gradual decrease in size due to filling of 4F.
• Oxidation state — the formal charge state of an element in a compound.
• Catalyst — a substance that increases the rate of a chemical reaction.
• Paramagnetism — attraction in a magnetic field due to unpaired electrons.

Action Items / Next Steps

• Revise the compounds of D and F blocks.
• Memorize the main oxidation states and electronic configurations.
• Write the preparation and reaction uses of Potassium Dichromate and Potassium Permanganate.