Oxidation States and Trends in Physical and Chemical Properties — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in Oxidation States and Trends in Physical and Chemical Properties.

Comparative stability of +3 and +5 oxidation states for Sb and Bi.

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The inert pair effect is a fundamental concept for p-block elements, and its manifestation in the stability of oxidation states for heavier Group 15 elements (Sb, Bi) is a classic and frequently tested topic. Questions often involve comparing the stability of halides or oxides (e.g., $SbCl_3$ vs $SbCl_5$, $Bi_2O_3$ vs $Bi_2O_5$) and asking for the reason behind the observed trend. This tests both conceptual understanding and specific knowledge of the inert pair effect.

Order of basicity or reducing character of Group 15 hydrides ($EH_3$).

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The trends in properties of hydrides ($EH_3$) are a cornerstone of Group 15 chemistry. Specifically, the decreasing basicity and increasing reducing character down the group are directly linked to bond strength and atomic size. These are very common comparative questions in NEET, requiring students to rank the hydrides based on a given property. Understanding the underlying reasons (e.g., lone pair availability for basicity, E-H bond strength for reducing character) is key.

Anomalous behavior of Nitrogen, particularly its inability to form pentahalides.

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Nitrogen's unique position as the first element in Group 15 leads to several anomalous properties, primarily due to its small size, high electronegativity, and absence of d-orbitals. The inability to form pentahalides (like $NCl_5$) while Phosphorus does ($PCl_5$) is a classic distinguishing feature and a common conceptual question. This tests the understanding of orbital availability and octet expansion.