NEET Chemistry - Chapter 11

Classification of Elements and Periodicity in Properties

Fresh NEET chemistry notes on modern periodic law, effective nuclear charge, periodic trends, and their chemical consequences.

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1. Modern Periodic Law and Table Structure

Modern periodic law states that the physical and chemical properties of elements are periodic functions of their atomic numbers. The recurring pattern appears because valence-shell electronic configurations repeat.

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2. Atomic Size and Ionization Trends

Across a period, atomic radius generally decreases and ionization enthalpy generally increases because effective nuclear charge rises. Down a group, increasing shell number dominates and size grows.

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3. Electron Gain Enthalpy and Electronegativity

Halogens strongly attract electrons, while noble gases are largely inert. Electronegativity rises across a period and falls down a group, peaking at fluorine.

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4. Metallic Character and Oxide Nature

Metallic character grows down a group and weakens across a period. The nature of oxides shifts from basic through amphoteric toward acidic across a period.

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5. Important Exceptions and Exam Traps

Many NEET questions are about exceptions such as the unusually less negative electron gain enthalpy of fluorine compared with chlorine and the ionization-enthalpy anomalies around Be/B and N/O.

Practice Tests

5 Chapter Tests of 25 Questions Each

Each test is original, NEET-aligned, and answer-backed. Use them as sectional revision instead of a single long mock so your weak subtopics become easier to identify quickly.

Test 1: Periodic Table Basics

Modern periodic law, periods, groups, and blocks.

Test 2: Atomic Size and Ionization

Radius, effective nuclear charge, and ionization trends.

Test 3: Electron Gain and Electronegativity

Electron affinity trends, electronegativity, and non-metallic character.

Test 4: Metallic Character and Oxides

Basic-acidic oxide behavior, metallic trends, and group comparisons.

Test 5: Mixed NEET Drill

Integrated periodicity concepts with exceptions and trend logic.

Open Practice Tests

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Move straight from chapter-wise questions into a subject test, then loop back into weaker areas instead of ending the session here.

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