d-block elements: Groups 3-12 where the d orbitals are progressively filled.
f-block elements: Contained in a separate panel, featuring elements where 4f and 5f orbitals are filled, known as lanthanoids and actinoids.
Transition Metals: Generally have incomplete d subshells and exhibit properties like variable oxidation states, formation of colored ions, and catalytic properties.
Inner Transition Metals: Lanthanoids and actinoids with complex chemistry due to various oxidation states and radioactivity (actinoids).
Series of Transition Metals
3d series: Sc to Zn
4d series: Y to Cd
5d series: La, Hf to Hg
6d series: Ac, Rf to Cn
Characteristics of Transition Metals
Electronic Configurations: Typically (n-1)d1-10 ns1-2. Exceptions exist due to small energy differences between (n-1)d and ns orbitals (e.g., Cr, Cu).
Physical Properties: High tensile strength, ductility, malleability, high thermal and electrical conductivity, high melting and boiling points.
Trends: Melting points peak at d5 configuration; atomic and ionic sizes decrease across the series due to increasing nuclear charge.
Magnetic Properties: Generally paramagnetic due to unpaired d electrons.
Oxidation States
Transition metals exhibit multiple oxidation states due to the participation of d electrons.
The most common oxidation states are +2 and +3, but some elements (e.g., Mn) can have states from +2 to +7.
Stability and Reactivity
Enthalpies of Atomisation: High due to strong interatomic interactions.
Ionisation Enthalpies: Increase across a period but not as sharply as in s- or p-block elements.
Standard Electrode Potentials (Eo): Reflect the ease of formation of ions, with Cu exhibiting unique behavior due to its positive Eo value.
f-block Elements
Lanthanoids: Exhibit +3 oxidation state predominantly; lanthanoid contraction affects chemistry.
Actinoids: Have variable oxidation states and exhibit more complex chemistry; contraction similar to lanthanoids.
Applications
Transition metals are used in construction, catalysis (e.g., V2O5 in sulfuric acid production), and as alloys.
Potassium dichromate and permanganate are key oxidising agents.
Important Compounds
Potassium Dichromate (K2Cr2O7): Used in leather tanning and as an oxidising agent.
Potassium Permanganate (KMnO4): Used in organic chemistry, textile bleaching, and as an oxidant.
Conclusion
The d- and f-block elements play pivotal roles in various industrial and chemical processes due to their unique chemical and physical properties.
Understanding the electronic configurations, oxidation states, and properties of these elements is crucial for their application in science and technology.