Statement-1: The third ionization enthalpy of La, Gd and Lu are abnormally low.
Statement-2: Empty, half-filled and completely filled orbitals of f-level are extra stable.

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Statement-1 is true, Statement -2 is false.

Statement-1 is True, Statement-2 is True, Statement-2
is NOT a correct explanation for Statement-1

Statement-1 is True, Statement-2 is True; Statement-2
is a correct explanation for Statement-1

Statement-1 is false, Statement -2 is true.

answer is A.

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Detailed Solution

The electronic configuration are,

${La}^{3 +} ⟶ 4 f^{0}$

${Gd}^{3 +} ⟶ 4 f^{7}$

${Lu}^{3 +} ⟶ 4 f^{14}$

La, Gd, and Lu have very low third ionization enthalpies. because f-level orbitals that are vacant, somewhat filled, or entirely filled are more stable.

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