Q14 / 75 · JEE Main 2026 (21 January Shift 2) · Chemistry

Given below are two statements :
Statement I : The correct order in terms of atomic/ionic radii is $\mathrm{Al}>\mathrm{Mg}>\mathrm{Mg}^{2+}>\mathrm{Al}^{3+}$.
Statement II : The correct order in terms of the magnitude of electron gain enthalpy is $\mathrm{Cl}>\mathrm{Br}>\mathrm{S}>\mathrm{O}$.
In the light of the above statements, choose the correct answer from the options given below :

  • A
    Both Statement I and Statement II are false
  • B
    Both Statement I and Statement II are true
  • Correct answer
    C
    Statement I is false but Statement II is true
  • D
    Statement I is true but Statement II is false

Solution

Analyzing Statement I: The order given is Al > Mg > Mg²⁺ > Al³⁺. However, the correct atomic radii order should be Mg > Al because Mg is in group 2 (period 3) while Al is in group 13 (period 3), and moving right across a period decreases radius. The correct order would be Mg > Al > Mg²⁺ > Al³⁺. Therefore, Statement I is FALSE.

Analyzing Statement II: Electron gain enthalpy magnitudes follow: Cl (highest, ~349 kJ/mol) > Br (~325) > S (~200) > O (~141). This is because Cl has the highest tendency to gain an electron due to its position and electronic configuration. Statement II is TRUE.

Since Statement I is false and Statement II is true, the answer is option (3).

Hence, the correct answer is option: 'C'.

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