CHEMISTRY SENIOR 4 Student's book Kigali, January 2019 Copyright © 2019 Rwanda Education Board All rights reserved. This book is the property of Rwanda Education Board. ii Chemistry Senior Four Student's Book FOREWORD Dear Student, Rwanda Education Board is honoured to present to you this Chemistry Book for Senior four which serves as a guide to competence-based teaching and learning to ensure consistency and coherence in the learning of chemistry subject. The Rwandan educational philosophy is to ensure that you achieve full potential at every level of education which will prepare you to be well integrated in society and exploit employment opportunities. The government of Rwanda emphasizes the importance of aligning teaching and learning materials with the syllabus to facilitate your learning process. Many factors influence what you learn, how well you learn and the competences you acquire. Those factors include the instructional materials available among others. Special attention was paid special attention to the activities that facilitate the learning process in which you can develop your ideas and make new discoveries during concrete activities carried out individually or with peers. In competence-based curriculum, learning is considered as a process of active building and developing knowledge and meanings by the learner where concepts are mainly introduced by an activity, a situation or a scenario that helps the learner to construct knowledge, develop skills and acquire positive attitudes and values. For effective use of this textbook, your role is to: • Work on given activities which lead to the development of skills • Share relevant information with other learners through presentations, discussions, group work and other active learning techniques such as role play, case studies, investigation and research in the library, from the internet or from your community; • Participate and take responsibility for your own learning; • Draw conclusions based on the findings from the learning activities. I wish to sincerely extend my appreciation to the people who contributed towards the development of this book, particularly REB staff who organized the whole process from its inception. Special gratitude goes to the University of Rwanda which provided experts in design and layout services, illustrations and image anti- plagiarism, lecturers and teachers who diligently worked to successful completion of this book. Any comment or contribution would be welcome for the improvement of this textbook for the next edition. Dr. Irénée NDAYAMBAJE Director General of Rwanda Education Board Chemistry Senior Four Student's Book iii ACKNOWLEDGEMENT I wish to express my appreciation to all the people who played a major role in development of this Chemistry textbook for senior four. It would not have been successful without active participation of different education stakeholders. I owe gratitude to different Universities and schools in Rwanda that allowed their staff to work with REB in the in-house textbooks production project. I wish to extend my sincere gratitude to lecturers, teachers and all other individuals whose efforts in one way or the other contributed to the success of writing of this textbook. Special acknowledgement goes to the University of Rwanda which provided experts in design and layout services, illustrations and image anti-plagiarism. Finally, my word of gratitude goes to the Rwanda Education Board staff particularly those from the department of curriculum who were involved in the whole process of in-house textbook writing. Joan MURUNGI, Head of Curriculum, Teaching and Learning Resources Department Chemistry Senior Four Student's Book v ACRONYMS AND ABBREVIATIONS 0C Celcius degree Atm Atmosphere Bpt Boiling point Ea Activation energy I.E Ionization energy K Kelvin degree KE Kinetic energy ME Mechanic energy Mpt Melting point Pa Pascal PE Potential energy VBT Valence bond theory VSEPR Valence shell electron pair repulsion vi Chemistry Senior Four Student's Book INTRODUCTION NOTE FOR THE STUDENT Senior four advanced level chemistry student book is part of three series of versions (Senior 5 ,Senior 6) required to help learners to complete the advanced level competence based syllabus developed by Rwanda Education Board (REB). The content here in was developed based on syllabus by experienced teachers, Rwanda Education Board subject specialists and senior lecturers from University of Rwanda. This version covers 18 units: structure of an atom and mass spectrum, electron configurations of atoms and ions, formation of ionic and metallic bonds, covalent bond and molecular structures, variation of trends of the physical properties on the periodic table, trends in chemical properties of group 1 elements and their compounds, trends in chemical properties of group 2 elements and their compounds, trends in chemical properties of group 13 elements and their compounds, trends in chemical properties of group 14 elements and their compounds, trends in chemical properties of group 15 elements and their compounds, trends in chemical properties of group 16 elements and their compounds, trends in chemical properties of group 17 elements and their compounds, properties and uses of group 18 elements , trends in chemical properties of period 3 elements and their compounds, factors that affect equilibrium, acids and bases, reduction and oxidation reactions and energy changes and energy profile diagrams for chemical reactions. This version is organized in a simple way to facilitate individual reading by the student her/ himself. At the beginning of each unit, there is an introductory activity mainly intended to relate the content in the unit and give the pre-knowledge, prerequisite knowledge about the unit and the relationship between the unit and daily life applications. Thereafter, you find a number of learning activities/practical activities and checking up activities that can help the learner to conceptualize the content and assist the learner to master the content and hence to pass national examinations and other internal examinations prepared by teacher and apply the acquired knowledge in his/her daily life. At the end of each unit a learner is expected to attempt and answer the questions reffered to as end unit assessment. These questions are prepared to help the learner develop the skills, values and attitudes covered within the unit. If the learner finds it difficult to attempt the questions then he/she is expected to review the unit and if necessary to seek help from his/her teacher. Chemistry Senior Four Student's Book vii Table of Content FOREWORD iii ACKNOWLEDGEMENT v ACRONYMS AND ABBREVIATIONS v i INTRODUCTION NOTE FOR THE STUDENT vii UNIT 1: STRUCTURE OF AN ATOM AND MASS SPECTRUM 2 1.1. Outline of the discovery of the atom constituents and their properties 4 1.2. Concept of atomic number, mass number, and isotopic mass 1 1 1.3. Calculation of relative atomic mass of elements with isotopes 1 3 1.4. Description and functioning of the mass spectrometer 1 5 1.5. Interpretation of mass spectra. 2 1 1.6. Uses of the mass spectrometer and involving calculations 2 5 1.7. End unit assessment 2 8 UNIT 2: ELECTRONIC CONFIGURATION OF ATOMS AND IONS 3 4 2.1. Bohr’s atomic model and concept of energy levels 3 5 2.2. Hydrogen spectrum and spectral lines 3 7 2.3. Atomic spectra 4 2 2.4 Orbitals and Quantum Numbers 4 3 2.5 Electronic configuration of atoms and ions 4 8 2.6. Relationship between ionization energy, energy levels and factors influencing ionization energy 5 4 2.7. End unit assessment 5 8 UNIT 3: FORMATION OF IONIC AND METALLIC BONDS 6 4 3.1. Stability of atoms and why they bind together 6 6 3.2. Ionic bonding 6 7 3.3. Formation of metallic bonds and physical properties of metals 8 1 3.4. End Unit Assessment 9 0 UNIT 4: COVALENT BOND AND MOLECULAR STRUCTURE 9 8 4.1. Overlap of atomic orbitals to form covalent bonds 9 9 4.2. Theories on the formation of covalent bond 103 4.3 Coordinate or dative covalent bonding and properties 110 viii Chemistry Senior Four Student's Book 4.4 Valence bond theory (VBT) 113 4.5 Valence Shell Electron Pair Repulsion Theory (VSEPR) theory 116 4.6. Hybridisation and types of Hybridisation 119 4.7 Polar covalent bonds 126 4.8. Simple and giant covalent structures 129 4.9. Intermolecular Forces 134 4.10. End unit assessment 139 UNIT 5: VARIATION IN TRENDS OF THE PHYSICAL PROPERTIES 148 5.1. Historical Background of the Periodic Table 149 5.2. Comparison of Mendeleev’s Table and Modern Periodic Table 152 5.3. Location of Elements in the Periodic Table Based On the Electronic Configuration 155 5.4. Classification of Elements into Blocks (s, p, d, f-block) 158 5.5. Characteristics of different blocks of the periodic table 159 5.6. Variation of Physical Properties down the Groups and across the Periods 162 5.7. End unit assessment 170 UNIT 6: TRENDS IN CHEMICAL PROPERTIES OF GROUP 1 ELEMENTS AND THEIR COMPOUNDS 174 6.1. Occurrence and physical properties of group 1 elements, physical state, metallic character, physical appearance and melting point 175 6.2. Reactivity of group 1 elements with oxygen, water and halogens 178 6.3. Properties of group 1 oxides and hydroxides 182 6.4. The effect of heat on Group 1 carbonates and nitrates 184 6.5. Solubility of group 1 compounds 187 6.6. Flame Test for Li+, Na+ and K+ 188 6.7. Uses of group 1 elements and their compounds 190 6.8 Hydrogen 191 6.9. End unit assessment 194 UNIT 7: TRENDS IN CHEMICAL PROPERTIES OF GROUP 2 ELEMENTS AND THEIR COMPOUNDS 198 7.1. Occurrence and physical properties of group 2 elements 199 7.2. Reactivity of group 2 elements 201 7.3. Properties of group 2 compounds 204 7.4. Anomalous properties of beryllium compounds 208 Chemistry Senior Four Student's Book ix 7.5.