IEMJEE Chemistry preparation: Periodic atomic-radius reasoning — practice worksheet with answers

How to use this worksheet

This independent worksheet checks periodic atomic-radius reasoning with a new problem, an explanation task and an interleaved related skill. It is not an official IEM question paper, a difficulty forecast or a prescribed timed examination.

Write an attempt first, then compare your method with the visible answers. Record whether a miss came from interpretation, a missing concept, execution or a condition you overlooked.

Question 1: apply the topic

Across a typical period, why can radius decrease as proton count increases?

Answer and checking point

Electrons enter the same main shell while effective nuclear attraction generally rises.

Check atom and charge bookkeeping, units, signs and the identity of the species to which a statement applies. For an organic transformation, retain the substrate and conditions. A familiar reagent or periodic trend is not enough to prove every proposed product or comparison.

Question 2: diagnose an approach

Explain why the following warning matters and identify the correction it calls for: A trend is not a substitute for distinguishing atomic, ionic and covalent-radius definitions.

Model checkpoint: Atomic size reflects competing nuclear attraction and shell occupancy. Trends are broad patterns with context-dependent exceptions. Governing rule: Across a period, effective nuclear attraction commonly contracts atomic size; down a group, added shells commonly increase it.

Question 3: transfer to biomolecule functional groups

Does recognising a hydroxyl group alone prove a molecule is a carbohydrate?

Answer: No. Many non-carbohydrates contain hydroxyl groups.

This is an interleaved related-skill task, not a claim that the two topics have identical methods. Explain which idea changes when switching from the main topic to this one.

Review the attempt

Separate correct answers reached with a justified method from lucky guesses. Rework missed steps without looking at the answer, then use a fresh problem from an appropriate primary textbook or official paper. Do not use a small worksheet result as an admission cutoff, rank or readiness guarantee.

Official sources and verification

Sources checked on 26 October 2026. A source’s date, programme and campus limit which claims it supports. Official pages may change after review.

1. UEM — IEMJEE examination information

   Historical examination pattern; verify the current cycle on the central portal.

2. NTA — explicitly labelled JEE Main 2026 syllabus

   Historical PCM syllabus reference. Lessons and exercises are independently authored, not official IEMJEE papers or verified 2027 paper predictions.

3. NCERT — official textbook catalogue

   Primary textbook reference for checking school-level concepts. This directory does not certify the independent lesson or establish IEM examination weightage.

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