Which of the following profound chemical and physical consequences strictly arise as a direct, obser — d and f Block Elements Chemistry Question

💡 Solution & Explanation

The poor shielding of the $4f$ electrons causes the Lanthanide contraction (a steady shrinking of size). Consequences include: (1) Post-lanthanide pairs like $Zr/Hf$ ($4d/5d$) have identical sizes and similar chemical properties. (2) The decreasing size of $Ln^{3+}$ increases covalency, thus decreasing the basicity of $Ln(OH)_3$. (3) Because $5d$ elements have roughly the same volume as $4d$ elements but significantly more mass, their densities are exceedingly high (e.g., Osmium/Iridium). Option D is completely false; $+3$ is universally favored.