NJC Physical Periodicity_student version 2023

National Junior College SH1 H2 Chemistry 1 Physical Periodicity of Elements 1 Introduction to Periodic Table Success criteria  I can recognize the variations in the valence electronic configuration across the Period and down a Group. Mankind had always been seeking to discover new chemical elements since centuries ago. As of January 2021, a total of 118 elements have been identified. Studying these hundreds of elements with different physical and chemical properties will surely be a daunting task, unless there is a systematic and organized way to do it. Much of what we will cover in this topic is credited to the Russian chemist Dmitri Ivanovich Mendeleev (1834-1907), whose seminal hypothesis that the chemical and physical properties of the elements vary in a periodic way laid the foundations of the modern Periodic Table. The Periodic Table is a table of elements arranged by order of their atomic numbers in such a way that the periodic properties (chemical periodicity) of the elements are made clear. In fact, the Periodic Table is a masterpiece of organised chemical information. The standard form of Periodic Table includes periods (horizontal rows) and groups (vertical columns). The elements in the same period have th e same number of core electrons as that of the noble gas from previous period. Elements in the same group have the same number of valence electrons and hence similar chemical properties. Content Periodicity of physical properties of the elements: variation with proton number across the third period (sodium to chlorine) and down the group of: (i) atomic radius and ionic radius (ii) ionisation energy (iii) electronegativity Learning outcomes Trends and variations in atomic and physical properties For elements in the third period (sodium to chlorine), and in Group 2 (magnesium to barium) and Group 17 (chlorine to iodine) candidates should be able to: (a) describe and explain qualitatively the trends and variations in atomic radius, ionic radius, first ionisation energy and electronegativity: (i) across a Period in terms of shielding and nuclear charge (ii) down a Group in terms of increasing number of filled electronic shells, shielding and nuclear charge References 1. Hill, G. & Holman, J. (1992). Chemistry in Context, 6th edition. New York: Prentice Hall. 2. Ramsden, E. N. (1994). A Level Chemistry, 3rd edition. UK: Stanley Thornes (Publishers) Ltd. 3. Chemistry for Advanced Level, Peter Cann, Peter Hughes 4. A-level Chemistry, E.N. Ramsden 5. Chemistry: The Molecular Nature of Matter and Change, Martin S. Silberberg

National Junior College SH1 H2 Chemistry 2 Physical periodicity is th