NJC 4 Physical Periodicity

National Junior College SH1 H1 Chemistry 1 PHYSICAL PERIODICITY OF ELEMENTS Content: Periodicity of atomic properties of the elements: variation with proton number across the third period (sodium to chlorine) and down the group of: • atomic radius and ionic radius • ionisation energy • electronegativity Learning Outcomes required for H1 (8873) Chemistry: Trends and variations in atomic properties For elements in the third period (sodium to chlorine), and in Group 17 (chlorine to iodine) candidates should be able to: (l) Recognize variation in the electronic configurations across a Period and down a Group. (m) 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 All Rights Reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording or any other information storage and retrieval system, without prior permission in writing from the copyright owner. Copyright © 2022 National Junior College

National Junior College SH1 H1 Chemistry 2 1 INTRODUCTION TO THE PERIODIC TABLE Mankind had always been seeking to discover new chemical elements since centuries ago. As of January 2021 , a total o f 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 Dmitr i 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 the 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. Physical periodicity is the study of periodic trends whi