Physics X - Chapter 05: Periodic Classification of Elements
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Quick Revision Box: Periodic Classification
- Dobereiner's Triads (1817): Groups of 3 elements where middle element's atomic mass ≈ average of other two (e.g., Li, Na, K).
- Newlands' Law of Octaves (1866): Every 8th element has properties similar to 1st, like musical notes.
- Mendeleev's Periodic Table (1869): Arranged elements by atomic mass; left gaps for undiscovered elements.
- Mendeleev's Periodic Law: Properties are periodic functions of atomic masses.
- Modern Periodic Law (Moseley, 1913): Properties are periodic functions of atomic numbers.
- Modern Periodic Table: 18 Groups (vertical), 7 Periods (horizontal); based on atomic number.
- Groups: Vertical columns (1-18); elements have same valence electrons → similar chemical properties.
- Periods: Horizontal rows (1-7); elements have same number of electron shells.
- Atomic Size Trend: Decreases across period (← to →), increases down group (↑ to ↓).
- Metallic Character: Decreases across period, increases down group.
- Non-Metallic Character: Increases across period, decreases down group.
- Ionization Energy: Energy to remove electron; increases across period, decreases down group.
- Electronegativity: Atom's electron-attracting ability; increases across period, decreases down group.
- Valency: Group 1-2: same as group number; Group 13-18: (18 - group number) for non-metals.
- Group 1: Alkali metals (Li, Na, K...); 1 valence electron; highly reactive; form basic oxides.
- Group 2: Alkaline earth metals (Be, Mg, Ca...); 2 valence electrons.
- Group 17: Halogens (F, Cl, Br...); 7 valence electrons; highly reactive non-metals.
- Group 18: Noble gases (He, Ne, Ar...); complete valence shells; inert; valency = 0.
- Oxide Nature: Metals → basic oxides; Non-metals → acidic oxides; Metalloids → amphoteric oxides.
- Blocks: s-block (Groups 1-2), p-block (Groups 13-18), d-block (transition metals), f-block (lanthanides/actinides).
Basic Level Questions
Chapter Summary: Periodic Classification of Elements
Imagine trying to organize 118 different elements without any system—it would be chaos! This chapter takes you on a fascinating journey through history, showing how scientists gradually discovered patterns in elemental properties and created the elegant periodic table we use today. You'll learn why sodium and potassium behave similarly, why fluorine is the most reactive non-metal, and how the table's structure predicts elements' behavior even before they're discovered.
Our platform transforms periodic table study from memorization to intuitive understanding. With 130+ carefully crafted MCQs, we help you visualize trends, practice electronic configuration-to-position conversions, and apply group characteristics to predict behavior. Questions on historical developments ensure you remember who contributed what, while trend-based questions with explanations build your reasoning skills. The graduated difficulty levels take you from basic group identifications to complex trend analysis and exception handling. This systematic practice builds both speed and accuracy, ensuring you can quickly locate elements, predict properties, and explain trends—turning the periodic table from a daunting chart into your most reliable scoring tool in chemistry exams.