Choose the statements which are incorrect in the case of Lanthanoids. A. Ce ⁴⁺ is diamagnetic while Sm ³⁺ is paramagnetic. B. The atomic size of the transition metals having atomic number greater than 71 are very close to that of the elements above them. C. Lanthanoids react with hot water forming water soluble Ln ( OH )₃ with the liberation of O ₂ . D. The general electronic configuration of Lanthanoids is (n-2) f¹⁻

Step-by-step solution

A. Correct: Ce⁴⁺ has [Xe]4f^0 configuration — all electrons paired, hence diamagnetic. Sm³⁺ has [Xe]4f^5 — unpaired f -electrons, hence paramagnetic. B. Correct: Due to lanthanoid contraction (poor shielding by 4f electrons), the 5d transition elements (atomic number > 71 ) have atomic/ionic radii remarkably similar to those of the 4d elements directly above them (e.g., Zr and Hf). C. Incorrect: Lanthanoids react with water liberating H₂ gas, not O₂ . Also, Ln(OH)₃ is sparingly soluble, not water soluble. 2Ln + 6H₂