Punjab Board Class 11 Chemistry — Flashcards for Quick Revision

A: Element: A pure substance containing only one type of atom. Examples: Iron (Fe), Oxygen (O₂), Copper (Cu). Atoms of one element cannot be separated by physical methods. Compound: A pure substance for

A: Mixture: A combination of two or more pure substances in any proportion where components retain their individual properties. Types: 1. Homogeneous Mixture: Components uniformly distributed throughout

A: 1. Solid: Definite shape and definite volume. Particles are tightly packed in orderly arrangement. Particles have very limited movement. Example: Ice, salt crystal. 2. Liquid: Definite volume but no

A: Thomson discovered the electron in 1897 through cathode ray experiments. He used perpendicular electric and magnetic fields to deflect cathode rays and measured their deflection. By balancing the elec

A: Given: e/m_e = 1.75882 × 10¹¹ C kg⁻¹ and e = 1.602176 × 10⁻¹⁹ C Formula: m_e = e ÷ (e/m_e) Step 1: m_e = (1.602176 × 10⁻¹⁹ C) ÷ (1.75882 × 10¹¹ C kg⁻¹) Step 2: m_e = 9.1094 × 10⁻³¹ kg Answer: The mass

A: Thomson's Model: Positive charge uniformly distributed throughout the atom with electrons embedded in it (like plums in pudding). Rutherford's Model: Positive charge concentrated in a tiny nucleus at

A: Modern Periodic Law: The physical and chemical properties of elements are periodic functions of their atomic numbers (Z), not atomic mass. Henry Moseley discovered this in 1913 by observing X-ray spec

A: Dobereiner's Law of Triads (1829): Elements arranged in groups of three showed a pattern where the middle element had properties intermediate to the other two, and its atomic weight was approximately

A: Mendeleev's bold decision to leave gaps in his 1905 Periodic Table demonstrated scientific insight and confidence. He predicted the existence of undiscovered elements (Eka-Aluminium/Gallium and Eka-Si