The F-block of the periodic table contains elements in which the last electron enters the f-orbital (specifically 4f or 5f orbitals). These elements are also called inner transition elements.
2. Position in the Periodic Table
Located separately at the bottom of the periodic table to keep it compact.
Consists of two series:
Lanthanides (4f series) – Atomic numbers 57 to 71 (from Lanthanum to Lutetium)
Actinides (5f series) – Atomic numbers 89 to 103 (from Actinium to Lawrencium)
3. General Characteristics
Valence Shell Configuration: (n-2)f¹–¹⁴ (n-1)d⁰–¹ (ns)²
Mostly metals with high melting and boiling points.
Show variable oxidation states.
Have a tendency to form colored ions due to f–f transitions.
Most are paramagnetic due to unpaired f-electrons.
Actinides are generally radioactive.
4. Lanthanides (4f Series)
Soft metals, high reactivity.
Common oxidation state: +3
Used in magnets, lasers, phosphors in TV and LED screens.
Examples: Cerium (Ce), Neodymium (Nd), Europium (Eu).
5. Actinides (5f Series)
All are radioactive.
Include naturally occurring elements like Thorium (Th), Uranium (U), and artificial ones like Plutonium (Pu).
Important in nuclear reactors and atomic weapons.
6. Applications
Lanthanides: Glass polishing, catalysts, high-strength magnets, electronics.
Actinides: Nuclear energy, medical radiation treatments, scientific research.
7. Quick Summary Table
| Series | Orbital Filled | Atomic Numbers | Key Traits |
|---|---|---|---|
| Lanthanides | 4f | 57–71 | Reactive metals, +3 oxidation state |
| Actinides | 5f | 89–103 | Radioactive, used in nuclear science |
