Before You Begin

Question #44122

Difficulty: 8/10 | 🟢 Free

The Question

Consider the aqueous uranium species: $U^{3+}(aq)$ , $U^{4+}(aq)$ , $UO_2^{+}(aq)$ , and $UO_2^{2+}(aq)$ at $298\text{ K}$ . Their corresponding hydroxides exhibit varying degrees of basic character. Which of the following options correctly identifies the Stock notation of Uranium in the least basic species, and provides the accurate structural rationale for this chemical behavior?

Options

A.
Uranium(VI); The species contains a discrete, linear covalent $O=U=O^{2+}$ motif where strong $p\pi-d\pi/f\pi$ bonding increases the effective positive charge at the metal center, making it the most acidic.
B.
Uranium(II); The $+2$ charge of the $UO_2^{2+}$ complex dictates its Stock notation, and its large effective ionic radius leads to low polarizing power and reduced basicity.
C.
Uranium(VI); The species exists as a bare $U^{6+}$ spherical cation with exceptionally high charge density, leading to complete ionic dissociation and minimal basicity.
D.
Uranium(IV); The $U^{4+}$ ion possesses the highest spherical charge density among the species, maximizing Fajans' polarization and resulting in the least basic hydroxide.

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Stock Notation Logic|Actinoid Oxidation State Variety|F-block Basic Character

Why This Question Is Tricky

Common Mistakes

The question tests the intersection of Stock notation, actinoid oxidation states, and the structural nuances of the f-block elements.

The primary trap is the misidentification of the oxidation state of $UO_2^{2+}$ as $+2$ (Option B) due to the overall charge of the complex ion, leading to an incorrect Stock notation.

A secondary trap is the misapplication of Fajans' rules by assuming U(VI) exists as a bare $U^{6+}$ spherical cation (Option C).

The key exception is the unique 'actinyl' structural motif ( $O=U=O^{2+}$ ), which dictates the covalent nature and the resulting acid-base properties, defying simple ionic models.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Redox Reactions - Class 11 Part 2
Concept	Stock Notation Logic
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free