NCERT Solutions for Class 11 Chemistry Chapter 3 Classification of Elements and Periodicity in Properties
NCERT Solutions for Class 11 Chemistry Chapter 3 Classification of Elements and Periodicity in Properties covers the development of the periodic table, the modern periodic law, and periodic trends in atomic properties.
Overview of Topics & Subtopics (Click to Jump)
1. Development of the Periodic Table
Short Note:
• Mendeleev's Periodic Law: properties of elements are a periodic function of their atomic masses (had limitations, e.g., placement of isotopes).
• Modern Periodic Law: properties of elements are a periodic function of their atomic numbers, which resolved the anomalies of Mendeleev's table.
2. Nomenclature of Elements with Atomic Number > 100
Short Note:
• IUPAC has recommended a systematic nomenclature using numerical roots for elements with atomic number greater than 100, until their names are officially confirmed.
3. Periodic Trends in Properties
Short Note:
• Atomic Radius: decreases across a period (left to right) due to increasing nuclear charge, and increases down a group due to addition of new shells.
• Ionization Enthalpy: generally increases across a period and decreases down a group.
• Electron Gain Enthalpy: generally becomes more negative across a period, and less negative down a group.
• Electronegativity: generally increases across a period and decreases down a group.
4. Periodic Trends in Chemical Reactivity
Short Note:
• Metallic character decreases across a period and increases down a group, while non-metallic character shows the opposite trend.
NCERT Textbook Exercise Questions
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