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p-Block Elements appeared 43 times across 3 years — 5% of Chemistry. This question is from Periodic Trends in Group 13 Elements.

Year 2026 2025 2024 Total
Questions 16 14 13 43
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The correct orders among the following are : - Atomic radius: B < Al < Ga < In < Tl - Electronegativity: Al < Ga < In < Tl < B - Density: Tl < In < Ga < Al < B - 1st Ionisation Energy: In < Al < Ga < Tl < B Choose the correct answer from the options given below :

Solution & Explanation

Related Formula

Group 13 elements (B, Al, Ga, In, Tl) show highly anomalous periodic trends due to the intervention of filled d-orbitals (d-block contraction in Ga) and f-orbitals (lanthanoid contraction in Tl).

Core Logic

Evaluate each specified trend against official physical constants:

  • Atomic radius: Due to d-block contraction, gallium (Ga) is smaller than aluminum (Al):
Radius (pm): B(88) < Ga(135) < Al(143) < In(167) < Tl(170)

Hence, the given order is Incorrect.

  • Electronegativity: Electronegativity first decreases from B to Al, then increases down the group due to poor shielding of d and f electrons:
Electronegativity: Al(1.5) < Ga(1.6) < In(1.7) < Tl(1.8) < B(2.0)

Hence, this order is Correct.

Step 1: Analyze density and ionization energy trends
  • Density: Increases down the group as atomic mass increases much faster than atomic volume:
Density (g/cm³): B(2.35) < Al(2.70) < Ga(5.90) < In(7.31) < Tl(11.85)

Hence, the given order is Incorrect (it is completely reversed).

  • 1st Ionisation Energy: Shows an irregular trend due to ineffective shielding by d and f electrons:
IE₁~(kJ/mol): In(558) < Al(577) < Ga(579) < Tl(589) < B(801)

Hence, this order is Correct.

Step 2: Conclusion

Only the Electronegativity (B) and 1st Ionisation Energy (D) orders are correct, matching Option (1).

Pattern Recognition

Group 13 elements do not follow monotonic trends. The poor shielding of 3d¹⁰ and 4f¹⁴ electrons increases the effective nuclear charge on valence electrons, causing anomalies in atomic radius (Ga < Al) and pulling electronegativities and ionization energies upward as you go further down.

Chapter Mix

Class 11 Chemistry: The p-Block Elements Class 11 Chemistry: Classification of Elements and Periodicity in Properties

Reference Study Guides

The P Block Elements

More The p-Block Elements Previous-Year Questions — Page 9

Q64 jee_main_2024_31_jan_evening Properties of Sulphur and Halogens
Given below are two statements: Statement I: S₈ solid undergoes disproportionation reaction under alkaline conditions to form S²⁻ and S₂O₃²⁻ Statement II: ClO₄^- can undergo disproportionation reaction under acidic condition. In the light of the above statements, choose the most appropriate answer from the options given below:
  • A. Statement I is correct but statement II is incorrect.
  • B. Statement I is incorrect but statement II is correct
  • C. Both statement I and statement II are incorrect.
  • D. Both statement I and statement II are correct.

Solution

Core Logic

Statement I: S₈ disproportionates in alkaline medium to give sulphide (S²⁻) and thiosulphate (S₂O₃²⁻). The reaction is:

S₈ + 12OH^- arrow 4S²⁻ + 2S₂O₃²⁻ + 6H₂O

This is a correct statement.

Statement II: ClO₄^- contains chlorine in its highest possible oxidation state of +7. A species can undergo disproportionation only if the element can exist in both higher and lower oxidation states than the present one. Since chlorine cannot exceed +7, ClO₄^- cannot undergo disproportionation. This is an incorrect statement.

Step 1: Final Conclusion

Statement I is correct, and Statement II is incorrect. Therefore, option (1) is the correct answer.

Chapter Mix

Class 11 Chemistry: Redox Reactions Class 12 Chemistry: The p-Block Elements

Q61 jee_main_2024_31_jan_morning Group 18 Elements
Give below are two statements: Statement-I: Noble gases have very high boiling points. Statement-II: Noble gases are monoatomic gases. They are held together by strong dispersion forces. Because of this they are liquefied at very low temperature. Hence, they have very high boiling points. In the light of the above statements, choose the correct answer from the options given below:
  • A. Statement I is false but Statement II is true.
  • B. Both Statement I and Statement II are true.
  • C. Statement I is true but Statement II is false.
  • D. Both Statement I and Statement II are false.

Solution

Core Logic

Statement I and II are False.

Noble gases have low boiling points. Noble gases are held together by weak dispersion forces.

Pattern Recognition

Noble gases are characterized by extremely weak intermolecular forces (London dispersion forces) because they are monoatomic and non-polar, which directly results in very low boiling and melting points.

Chapter Mix

Class 12 Chemistry: The p-Block Elements

Q79 jee_main_2024_31_jan_morning Group 14 Elements
Consider the oxides of group 14 elements SiO₂, GeO₂, SnO₂, PbO₂, CO and GeO. The amphoteric oxides are
  • A. GeO, GeO₂
  • B. SiO₂, GeO₂
  • C. SnO₂, PbO₂
  • D. SnO₂, CO

Solution

Core Logic

In Group 14 elements, the nature of oxides varies down the group: CO is neutral. CO₂ and SiO₂ are acidic. GeO₂ is distinctly acidic. SnO₂ and PbO₂ are amphoteric.

Pattern Recognition

Tin (Sn) and Lead (Pb) mostly form amphoteric oxides (e.g., SnO, SnO₂, PbO, PbO₂), distinguishing them from the acidic oxides of Carbon and Silicon.

Chapter Mix

Class 11 Chemistry: The p-Block Elements

More The p-Block Elements Questions — jee_main_2025_03_april_evening

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