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Classification of Elements and Periodicity in Properties appeared 36 times across 3 years — 4.2% of Chemistry. This question is from Atomic/Ionic Radii and Electron Gain Enthalpy.

Year 2026 2025 2024 Total
Questions 9 16 11 36

Given below are two statements: Statement-I: The correct order in terms of atomic/ionic radii is Al > Mg > Mg²⁺ > Al³⁺. 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:

Solution & Explanation

Core Logic
  • Statement I: Correct order of size is Mg > Al > Mg²⁺ > Al³⁺ because atomic radius of magnesium is greater than aluminium in period 3. Thus Statement-I is false.
  • Statement-II: Chlorine has the highest electron gain enthalpy in the periodic table, and halogens exceed chalcogens. The order Cl > Br > S > O is true.
Step 1: Final Conclusion

Statement I is false but Statement II is true, corresponding to option (2).

Pattern Recognition

Sees: Periodic trends for atomic radii and electron affinity. Trap: Assuming Al is larger than Mg due to higher atomic number.

Chapter Mix

Class 11 Chemistry: Classification of Elements and Periodicity in Properties

Reference Study Guides

More Classification of Elements and Periodicity in Properties Previous-Year Questions — Page 8

Q70 jee_main_2024_31_jan_morning Electron Gain Enthalpy
The correct sequence of electron gain enthalpy of the elements listed below is A. Ar B. Br C. F D. S Choose the most appropriate from the options given below:
  • A. C > B > D > A
  • B. A > D > B > C
  • C. A > D > C > B
  • D. D > C > B > A

Solution

Core Logic

Electron gain enthalpy (ΔegH) values are considered with their signs when ordering from largest to smallest algebraically.

ElementΔegH (kJ/mol)
F-333
S-200
Br-325
Ar+96

Arranging these algebraically from highest to lowest: +96 > -200 > -325 > -333 Thus, Ar > S > Br > F, which corresponds to A > D > B > C.

Pattern Recognition

Noble gases always have positive electron gain enthalpies (highest algebraically). Halogens have highly negative values (lowest algebraically). Fluorine is highly negative, Bromine is slightly less negative. Sulfur sits in between.

Chapter Mix

Class 11 Chemistry: Classification of Elements and Periodicity in Properties

More Classification of Elements and Periodicity in Properties Questions — jee_main_2026_21_jan_evening

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JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)