Classification of Elements and Periodicity in Properties – NEET Chemistry Class 11

Chemistry is one of the most scoring subjects in NEET, provided you understand the basic concepts clearly. One of the most important chapters for Class 11 students is Classification of Elements and Periodicity in Properties, which lays the foundation for understanding chemical behavior and the periodic table. In this guide, we provide a detailed overview along with insights from previous year NEET questions, helping students to prepare efficiently for their exams.

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Introduction to the Periodic Table

The Periodic Table is a tabular arrangement of chemical elements, organized by increasing atomic number and recurring chemical properties. Scientists like Dmitri Mendeleev and Henry Moseley played a key role in its development. Mendeleev arranged elements by atomic mass, while Moseley later corrected it to atomic number, which is the basis of the modern periodic law: “The properties of elements are a periodic function of their atomic numbers.”

Classification of Elements

Elements are broadly classified into Metals, Non-metals, and Metalloids based on their physical and chemical properties:

1. Metals – Solid (except mercury), lustrous, malleable, ductile, good conductors of heat and electricity. Examples: sodium (Na), calcium (Ca).

2. Non-Metals – Brittle, non-lustrous, poor conductors; can be solid, liquid, or gas. Examples: sulfur (S), oxygen (O).

3. Metalloids (Semi-Metals) – Show properties of both metals and non-metals. Examples: boron (B), silicon (Si).

Modern Periodic Law

The Modern Periodic Law states: “The physical and chemical properties of elements are periodic functions of their atomic numbers.” This law forms the basis of the Modern Periodic Table, which consists of:

• Periods: Horizontal rows (7 in total)

• Groups: Vertical columns (18 in total)

Elements in the same group show similar chemical properties due to identical valence electron configurations.

Periodic Trends in Properties

Understanding periodic trends is essential for NEET. The main trends include:

1. Atomic Radius – Distance from nucleus to outermost electron.

   • Across a period: Decreases due to increased nuclear charge.

   • Down a group: Increases due to added electron shells.

2. Ionization Energy – Energy needed to remove an electron.

   • Across a period: Increases.

   • Down a group: Decreases.

3. Electron Affinity – Energy change when an electron is added.

   • Across a period: Becomes more negative (except noble gases).

   • Down a group: Becomes less negative.

4. Electronegativity – Ability to attract electrons in a bond.

   • Across a period: Increases.

   • Down a group: Decreases.

5. Metallic & Non-Metallic Character –

   • Metallic character decreases across a period, increases down a group.

   • Non-metallic character shows the opposite trend.

Importance for NEET Preparation

The Classification of Elements and Periodicity chapter is crucial because:

• Many questions are concept-based, testing reasoning.

• Previous NEET papers frequently ask about trends like ionization energy and electronegativity.

• Helps in solving numerical and comparison-based problems quickly.

Previous Year NEET Questions – Insights

Questions from this chapter often cover:

• Identification of elements from electron configurations.

• Prediction of reactivity and metallic/non-metallic nature.

• Comparison of atomic and ionic radii.

• Trends in ionization energy, electron affinity, and electronegativity.

Study Tips for Students

1. Focus on Concepts – Understanding why properties change is better than memorization.

2. Use a Modern Periodic Table – Helps visualize element positions and trends.

3. Practice Previous Year Papers – Improves speed and accuracy.

4. Create Trend Charts – Useful for revision of periodic properties.

5. Solve NCERT Questions – Most NEET questions are NCERT-based.

Conclusion

Mastering Classification of Elements and Periodicity in Properties is essential for NEET success. Combining conceptual clarity with previous year paper practice allows students to confidently tackle both theoretical and application-based questions.