d and f Block Elements — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in d and f Block Elements.

Application of Lanthanoid Contraction

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Lanthanoid contraction is a fundamental concept with significant consequences. NEET frequently tests its effects, particularly the similar atomic radii of second and third transition series elements (e.g., Zr and Hf) and the resulting difficulty in their separation. A question might involve identifying pairs of elements with similar radii or asking for the reason behind this similarity. Understanding the poor shielding effect of 4f electrons is key here.

Redox Reactions of $KMnO_4$ and $K_2Cr_2O_7$

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Potassium permanganate and potassium dichromate are classic oxidizing agents from the d-block. Questions often involve their preparation, their oxidizing behavior in different media (acidic, basic, neutral), and the products formed. Balancing redox reactions involving these compounds or identifying the change in oxidation state of Mn/Cr is a common and high-yield question type. Students should be proficient with the half-reactions and overall balanced equations.

Magnetic Moment and Electronic Configuration of Ions

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This is a perennial favorite. Questions will ask to calculate the spin-only magnetic moment for a given transition metal ion or to identify an ion with a specific magnetic moment or magnetic property (paramagnetic/diamagnetic). The core skill tested is the ability to correctly write the electronic configuration of an ion (remembering to remove $ns$ electrons first) and then count the number of unpaired electrons. Exceptions in electronic configurations (Cr, Cu) are also often integrated.

Comparative Properties of Lanthanoids and Actinoids

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While less frequent than d-block questions, comparative analysis of f-block elements is important. Questions might ask to differentiate between lanthanoids and actinoids based on their oxidation states, radioactivity, extent of contraction, or chemical reactivity. Understanding why actinoids show a wider range of oxidation states (closer energy levels of 5f, 6d, 7s) and are all radioactive is crucial.