JEE Main 2026 Apr 6 Shift 1, Chemistry Q9: Periodicity In Atomic Properties

JEE Main2026Apr 6, Shift 1Chemistry

Given below are two statements:

Statement-I: Aluminium is more electropositive than thallium as the standard electrode potential value of $E_{Al^{3 +} / Al}^{\circ}$ is negative and $E_{Tl^{3 +} / Tl}^{\circ}$ is positive.

Statement-II: The sum of first three ionization enthalpies of boron is very high when compared to that of aluminium. Due to this reason boron forms covalent compounds only and aluminium forms $Al^{3 +}$ ion.

In the light of the above statements, choose the correct answer from the options given below.

A
Both Statement-I and Statement-II are true.
B
Both Statement-I and Statement-II are false.
C
Statement-I is true but Statement-II is false.
D
Statement-I is false but Statement-II is true.

Solution

Statement-I: $E_{Al^{3 +} / Al}^{\circ} = - 1.66$ V and $E_{Tl^{3 +} / Tl}^{\circ} = + 1.26$ V. A more negative reduction potential implies the metal is more easily oxidized, hence more electropositive. So Al is more electropositive than Tl. True.

Statement-II: $IE_{1} + IE_{2} + IE_{3}$ for B is approximately $801 + 2427 + 3659 \approx 6887$ kJ mol $^{- 1}$ , substantially higher than for Al ( $\approx 5137$ kJ mol $^{- 1}$ ). The very high cumulative ionization energy makes loss of three electrons impractical for B, so it bonds covalently; Al's lower values allow $Al^{3 +}$ formation. True.

$∴$ Both statements are true.

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JEE Main 2026 Apr 6 Shift 1, Chemistry Q9: Periodicity In Atomic Properties

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