COMEDK 2025 Morning Solved Paper

Concept:Matching lanthanoid and d-block metals with their characteristic properties based on electronic configuration and trends.Explanation:Property A: Lanthanoid with low third ionization enthalpy.Gadolinium (Gd) has a half-filled $4f$ subshell, giving it a stable configuration. This leads to a relatively low $3^{\text{rd}}$ ionization enthalpy. So A matches Q.Property B: f-block element with configuration $[\mathrm{Rn}]\,6d^2\,7s^2$.This is the configuration of thorium (Th). Hence B matches R.Property C: 3d-series metal whose $\mathrm{M}^{3+}_{(aq)}$ is colourless.Scandium (Sc) forms $\mathrm{Sc}^{3+}$ which has a $d^0$ configuration, making it colourless. Thus C matches S.Property D: 3d-series metal with highest enthalpy of atomisation.Vanadium (V) has the highest atomisation enthalpy among the 3d metals due to strong metallic bonding. So D matches P.Thus, the correct matching is: A → Q, B → R, C → S, D → P.Answer:Option A: $\mathrm{A}=\mathrm{Q},\ \mathrm{B}=\mathrm{R},\ \mathrm{C}=\mathrm{S},\ \mathrm{D}=\mathrm{P}$