4.1 Position in the Periodic Table
- d-Block elements: Groups 3–12
- Also called transition elements
- Characterized by partially filled d-orbitals
- f-Block elements: Lanthanoids and Actinoids
- Characterized by partially filled f-orbitals
- Located below the main periodic table
4.2 Electronic Configurations of the d-Block Elements
- General configuration:
(n−1)d1−10ns0−2
- Examples:
- Scandium (Sc): [Ar] 3d¹ 4s²
- Iron (Fe): [Ar] 3d⁶ 4s²
- d-Orbital filling leads to:
- Variable oxidation states
- Formation of colored compounds
4.3 General Properties of the Transition Elements (d-Block)
Physical Properties
- High melting and boiling points
- High density
- Hard and strong metals
- Conduct electricity and heat
Chemical Properties
- Multiple oxidation states
- Formation of colored compounds
- Act as good catalysts
- Form complex compounds
Other Properties
- Magnetic behavior: Paramagnetic or diamagnetic
- Form alloys and interstitial compounds
4.4 Some Important Compounds of Transition Elements
Examples
- Oxides
- Fe₂O₃, MnO₂
- Halides
- FeCl₃, TiCl₄
- Coordination compounds
- [Fe(CN)₆]³⁻, [Cu(NH₃)₄]²⁺
Properties
- Often colored
- Exhibit variable oxidation states
4.5 The Lanthanoids
- 14 elements from La to Lu
- 4f-orbitals are being filled
- Properties:
- Similar chemical behavior
- High melting points
- Reactivity decreases gradually (lanthanoid contraction)
4.6 The Actinoids
- 14 elements from Ac to Lr
- 5f-orbitals are being filled
- Properties:
- All are radioactive
- Exhibit multiple oxidation states
- Form complexes with ligands
4.7 Some Applications of d- and f-Block Elements
d-Block Elements
- Catalysts: Fe in Haber process, V₂O₅ in Contact process
- Alloys: Steel (Fe + C + others)
f-Block Elements
- Lanthanoids: Phosphors in TV tubes and LEDs
- Actinoids: Nuclear fuel (U, Pu)