Given below are two statements, one is labelled as Statement I and the other is labelled as Statement II. Statement I: The correct order in terms of atomic/ionic radii is Al Mg Mg 2+ Al 3+ . Statement II: The correct order in terms of the magnitude of electron gain enthalpy is Cl Br S O . In the light of the above statements, choose the correct answer from the options given below:

Statement I is false but Statement II is true

Both Statement I and Statement II are false

Statement I is true but Statement II is false

Both Statement I and Statement II are true

Chemistry · Periodicity of Elements and Periodic Properties

JEE Main 2026 — 21 January, Evening Shift — Question 55

Given below are two statements, one is labelled as Statement I and the other is labelled as Statement II.

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:

Option A:
Both Statement I and Statement II are false
Option B:
Statement I is false but Statement II is true
Correct
Option C:
Statement I is true but Statement II is false
Option D:
Both Statement I and Statement II are true

Answer: B

Step-by-step solution

Statement I: Across Period 3, atomic radius decreases from left to right. Thus, $\mathrm{Mg > Al}$ .

For cations, size decreases with increase in positive charge. Also $\mathrm{Mg^{2+}}$ and $\mathrm{Al^{3+}}$ are isoelectronic (10 electrons). In an isoelectronic series, radius decreases with increase in nuclear charge. Thus, $\mathrm{Mg^{2+} > Al^{3+}}$ .

Correct overall order is $\mathrm{Mg > Al > Mg^{2+} > Al^{3+}}$ .

Given order $\mathrm{Al > Mg}$ is incorrect. Hence, Statement I is false.

Statement II: Electron gain enthalpy (magnitude) among these follows $\mathrm{Cl > Br > S > O}$ . Chlorine has highest value. Oxygen has lower value than sulfur due to small size and greater repulsion. Thus, Statement II is true.

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 21 January, Evening Shift
Subject: Chemistry
Chapter: Periodicity of Elements and Periodic Properties
Topic: Periodicity in Chemical Properties (Ionization Energy, Electron Affinity, Electronegativity)