Chapter 8 Periodic Table and Periodicity Notes - Class 9 Chemistry Punjab Board
Chapter-wise notes for Class 9 Chemistry Chapter 8, Periodic Table and Periodicity, prepared for Punjab Board students, covering the modern periodic table, salient features, periodic properties including atomic radius, ionization energy, electron affinity and electronegativity, metallic character, and reactivity, with solved exercises and MCQs available to read online.
Chapter Overview
Chapter 8 of Class 9 Chemistry, Periodic Table and Periodicity, introduces students to the modern periodic table and the organizing principles that underpin it. The chapter begins with the salient features of the modern periodic table, including its arrangement of elements by increasing atomic number, the division into periods and groups, and the significance of the s, p, d, and f blocks. Students also study similarities in the chemical properties of elements within the same group, learning how elements in the same group have the same number of valence electrons and how this explains the relationship between group number and the charge of ions formed by those elements.
The chapter then examines how four key periodic properties vary across periods and down groups: atomic radius, which increases down a group and generally decreases across a period; ionization energy, which decreases down a group and generally increases across a period; electron affinity, the energy released when an atom gains an electron, which follows trends linked to atomic size and nuclear charge; and electronegativity, the ability of an atom to attract shared electrons in a bond, which increases across a period and decreases down a group. The chapter also connects these trends to metallic character and reactivity, noting that metals become more reactive down a group and non-metals become less reactive, and covers the variation in density across the periodic table.
For Punjab Board exam preparation, Periodic Table and Periodicity is one of the most data-rich chapters in Class 9 Chemistry, and questions on periodic trends appear consistently in MCQs and short questions across all Punjab Board examination centres including Lahore Board, Rawalpindi Board, Gujranwala Board, Faisalabad Board, Multan Board, and others. These notes are organized to help SSC Part 1 students learn and compare periodic trends systematically, with clear explanations for why each property increases or decreases in a given direction.