Question

Write a note on lanthanoids.

Answer 1

1. Lanthanoids are elements ranging from Lanthanum (₅₇La) to Lutetium (₇₁Lu).
2. They have incomplete 4f orbitals.
3. The standard electronic arrangement is
   [Xe]4 f^{0 -14} 5d^{0 -2} 6s².
4. From La to Lu, the atomic and ionic radii gradually decrease. This is referred to as lanthanoid contraction.