Jacaranda Chemistry VCE Units 1 & 2 Third Edition PDF
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Uploaded by Demarcus Cousins VII
2023
Robert Stokes, Angela Stubbs, Neale Taylor, Billie Murray, Kate Burrows, Maida Derbogosian, Santina Raphael, Sholto Bowen, Lakshmi Sharma
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This Jacaranda Chemistry VCE Units 1 & 2 textbook, third edition 2023, covers various chemistry topics including elements, molecular substances, and reactions. It is suitable for secondary school students.
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1 JACARANDA CHEMISTRY VCE UNITS 1 AND 2 | THIRD EDITION 1 JACARANDA CHEMISTRY VCE UNITS 1 AND 2 | THIRD EDITION ROBERT STOKES ANGELA STUBBS...
1 JACARANDA CHEMISTRY VCE UNITS 1 AND 2 | THIRD EDITION 1 JACARANDA CHEMISTRY VCE UNITS 1 AND 2 | THIRD EDITION ROBERT STOKES ANGELA STUBBS NEALE TAYLOR BILLIE MURRAY KATE BURROWS MAIDA DERBOGOSIAN SANTINA RAPHAEL SHOLTO BOWEN CONTRIBUTING AUTHOR Lakshmi Sharma Third edition published 2023 by John Wiley & Sons Australia, Ltd 155 Cremorne Street, Cremorne, Vic 3121 First edition published 2016 Second edition published 2020 Typeset in 10.5/13 pt TimesLTStd © Neale Taylor, Robert Stokes, Angela Stubbs, Belinda Maree Murray, Kate Burrows, Maria James, Sholto Bowen, Santina Raphael, Maida Derbogosian 2023 The moral rights of the authors have been asserted. ISBN: 978-1-1198-8431-6 Reproduction and communication for educational purposes The Australian Copyright Act 1968 (the Act) allows a maximum of one chapter or 10% of the pages of this work, whichever is the greater, to be reproduced and/or communicated by any educational institution for its educational purposes provided that the educational institution (or the body that administers it) has given a remuneration notice to Copyright Agency Limited (CAL). Reproduction and communication for other purposes Except as permitted under the Act (for example, a fair dealing for the purposes of study, research, criticism or review), no part of this book may be reproduced, stored in a retrieval system, communicated or transmitted in any form or by any means without prior written permission. All inquiries should be made to the publisher. Trademarks Jacaranda, the JacPLUS logo, the learnON, assessON and studyON logos, Wiley and the Wiley logo, and any related trade dress are trademarks or registered trademarks of John Wiley & Sons Inc. and/or its affiliates in the United States, Australia and in other countries, and may not be used without written permission. All other trademarks are the property of their respective owners. Front cover image: © Valenty/Shutterstock Illustrated by various artists, diacriTech and Wiley Composition Services Typeset in India by diacriTech All activities have been written with the safety of both teacher and student in mind. Some, however, involve physical activity or the use of equipment or tools. All due care should be taken when performing such activities. Neither the publisher nor the authors can accept responsibility for any injury that may be sustained when completing activities described in this textbook. Contents About this resource............................................................................................................................................................................................ix Acknowledgements.........................................................................................................................................................................................xvi UNIT 1 HOW CAN THE DIVERSITY OF MATERIALS BE EXPLAINED? 1 AREA OF STUDY 1 HOW DO THE CHEMICAL STRUCTURES OF MATERIALS EXPLAIN THEIR PROPERTIES AND REACTIONS? 1 Elements and the periodic table 3 1.1 Overview................................................................................................................................................................ 4 1.2 Elements................................................................................................................................................................ 5 1.3 Electrons............................................................................................................................................................. 12 1.4 The periodic table................................................................................................................................................ 25 1.5 Trends in the periodic table.................................................................................................................................. 32 1.6 Critical elements.................................................................................................................................................. 43 1.7 Review................................................................................................................................................................. 53 2 Covalent substances 59 2.1 Overview.............................................................................................................................................................. 60 2.2 Representing molecules...................................................................................................................................... 61 2.3 Shapes of molecules........................................................................................................................................... 73 2.4 Comparing intramolecular bonding and intermolecular forces............................................................................. 86 2.5 Physical properties of molecular substances....................................................................................................... 95 2.6 Structure and bonding of diamond and graphite................................................................................................. 99 2.7 Review............................................................................................................................................................... 107 3 Reactions of metals 113 3.1 Overview............................................................................................................................................................ 114 3.2 Properties of metals........................................................................................................................................... 115 3.3 Reactivity of metals........................................................................................................................................... 121 3.4 Recycling metals............................................................................................................................................... 129 3.5 Review............................................................................................................................................................... 139 4 Reactions of ionic compounds 145 4.1 Overview............................................................................................................................................................ 146 4.2 Structure and properties of ionic substances.................................................................................................... 147 4.3 Formation of ionic compounds.......................................................................................................................... 157 4.4 Precipitation reactions....................................................................................................................................... 165 4.5 A review of bonding........................................................................................................................................... 176 4.6 Review............................................................................................................................................................... 182 5 Separation and identification of the components of mixtures 187 5.1 Overview............................................................................................................................................................ 188 5.2 Solutions, solvents and chromatography........................................................................................................... 189 5.3 Review............................................................................................................................................................... 207 AREA OF STUDY 1 REVIEW.......................................................................................................................................... 215 Practice examination.......................................................................................................................................................215 Practice school-assessed coursework.............................................................................................................................222 CONTENTS v AREA OF STUDY 2 HOW ARE MATERIALS QUANTIFIED AND CLASSIFIED? 6 Quantifying atoms and compounds 225 6.1 Overview............................................................................................................................................................ 226 6.2 Relative isotopic mass and the carbon-12 scale................................................................................................ 227 6.3 Avogadro’s constant and the mole.................................................................................................................... 236 6.4 Using the mole concept..................................................................................................................................... 245 6.5 Review............................................................................................................................................................... 253 7 Families of organic compounds 259 7.1 Overview............................................................................................................................................................ 260 7.2 Hydrocarbon families......................................................................................................................................... 261 7.3 Naming organic compounds and isomers......................................................................................................... 275 7.4 Functional groups — alcohols and carboxylic acids.......................................................................................... 283 7.5 Sources and uses of organic chemicals............................................................................................................. 295 7.6 Review............................................................................................................................................................... 302 8 Polymers and society 309 8.1 Overview............................................................................................................................................................ 310 8.2 Polymers........................................................................................................................................................... 311 8.3 Linear and cross-linked polymers...................................................................................................................... 320 8.4 Polymer selection.............................................................................................................................................. 326 8.5 Plastic recycling and innovations in design........................................................................................................ 337 8.6 Review............................................................................................................................................................... 348 AREA OF STUDY 2 REVIEW.......................................................................................................................................... 355 Practice examination.......................................................................................................................................................355 Practice school-assessed coursework.............................................................................................................................361 AREA OF STUDY 3 HOW CAN CHEMICAL PRINCIPLES BE APPLIED TO CREATE A MORE SUSTAINABLE FUTURE? 9 Research investigations 9.1 Overview 9.2 Investigating how chemistry can create a more sustainable future 9.3 Scientific evidence, and analysing and evaluating sources 9.4 Models and theories to understand observed phenomena 9.5 Effective science communication 9.6 Review UNIT 2 HOW DO CHEMICAL REACTIONS SHAPE THE NATURAL WORLD? 367 AREA OF STUDY 1 HOW DO CHEMICALS INTERACT WITH WATER? 10 Water as a unique chemical 369 10.1 Overview............................................................................................................................................................ 370 10.2 Water on Earth................................................................................................................................................... 371 10.3 Properties of water............................................................................................................................................ 380 10.4 Heat capacity and latent heat............................................................................................................................ 388 10.5 Review............................................................................................................................................................... 398 vi CONTENTS 11 Acid–base (proton transfer) reactions 405 11.1 Overview............................................................................................................................................................ 406 11.2 Acids and bases................................................................................................................................................ 407 11.3 Concentration and strength of acids and bases................................................................................................ 415 11.4 The pH scale...................................................................................................................................................... 420 11.5 Measuring pH.................................................................................................................................................... 431 11.6 Neutralisation reactions to produce salts........................................................................................................... 443 11.7 Applications of acid–base reactions in society.................................................................................................. 452 11.8 Review............................................................................................................................................................... 456 12 Redox (electron transfer) reactions 463 12.1 Overview............................................................................................................................................................ 464 12.2 Redox reactions................................................................................................................................................. 465 12.3 EXTENSION: Oxidation numbers....................................................................................................................... 475 12.4 Reactivity series of metals................................................................................................................................. 481 12.5 Applications of redox reactions......................................................................................................................... 486 12.6 Review............................................................................................................................................................... 498 AREA OF STUDY 1 REVIEW.......................................................................................................................................... 505 Practice examination.......................................................................................................................................................505 Practice school-assessed coursework.............................................................................................................................511 AREA OF STUDY 2 HOW ARE CHEMICALS MEASURED AND ANALYSED? 13 Measuring solubility and concentration 513 13.1 Overview............................................................................................................................................................ 514 13.2 Measuring solution concentration...................................................................................................................... 515 13.3 Factors that influence solubility......................................................................................................................... 526 13.4 Solubility graphs................................................................................................................................................ 536 13.5 Review............................................................................................................................................................... 550 14 Analysis for acids and bases 557 14.1 Overview............................................................................................................................................................ 558 14.2 Solution stoichiometry (volume–volume stoichiometry)...................................................................................... 559 14.3 Acid–base titrations........................................................................................................................................... 568 14.4 Review............................................................................................................................................................... 581 15 Measuring gases 587 15.1 Overview............................................................................................................................................................ 588 15.2 Gases and the enhanced greenhouse effect...................................................................................................... 589 15.3 Gases at standard laboratory conditions (SLC).................................................................................................. 595 15.4 Calculations using the ideal gas equation and stoichiometry............................................................................. 603 15.5 Review............................................................................................................................................................... 610 16 Analysis for salts 615 16.1 Overview............................................................................................................................................................ 616 16.2 The sources of salts in soil and water................................................................................................................ 617 16.3 Quantitative analysis of salts — stoichiometry and molar ratios........................................................................ 624 16.4 Quantitative analysis of salts — colorimetry and UV-visible spectroscopy........................................................ 642 16.5 Review............................................................................................................................................................... 652 CONTENTS vii AREA OF STUDY 2 REVIEW.......................................................................................................................................... 659 Practice examination.......................................................................................................................................................659 Practice school-assessed coursework.............................................................................................................................667 AREA OF STUDY 3 HOW DO QUANTITATIVE SCIENTIFIC INVESTIGATIONS DEVELOP OUR UNDERSTANDING OF CHEMICAL REACTIONS? 17 Scientific investigations 17.1 Overview 17.2 Key science skills and concepts in chemistry 17.3 Characteristics of scientific methodology and primary data generation 17.4 Health, safety and ethical guidelines 17.5 Quality of data and measurements 17.6 Ways of organising, analysing and evaluating primary data 17.7 Challenging scientific models and theories 17.8 The limitations of investigation methodology and conclusions 17.9 Options related to analysing substances in water, acid–base or redox reactions, and production of gases 17.10 Presenting findings using scientific conventions 17.11 Review Answers............................................................................................................................................................................................. 671 Glossary............................................................................................................................................................................................. 733 Index.................................................................................................................................................................................................. 745 Periodic table of the elements......................................................................................................................................................... 752 viii CONTENTS About this resource YEAR 11 NEW FOR 2023 YEAR 12 COMING FOR 2024 JACARANDA CHEMISTRY 1 VCE UNITS 1 AND 2 THIRD EDITION Developed by expert Victorian teachers for VCE students Tried, tested and trusted. The NEW Jacaranda VCE Chemistry series continues to deliver curriculum-aligned material that caters to students of all abilities. Completely aligned to the VCE Chemistry Study Design Our expert author team of practising teachers and assessors ensures 100% coverage of the new VCE Chemistry Study Design (2023–2027). Everything you need for your students to succeed, including: NEW! Access targeted questions sets including exam-style questions and all relevant past VCAA exam questions since 2013. Ensure assessment preparedness with practice SACs. NEW! Enhanced practical investigation support including practical investigation videos, and eLogbook with fully customisable practical investigations — including teacher advice and risk assessments. NEW! Teacher-led videos to unpack challenging concepts, VCAA exam questions, exam-style questions, ABOUT THIS RESOURCE ix Learn online with Australia’s most Everything you need Trusted, curriculum-aligned theory Engaging, rich multimedia for each of your lessons All the teacher support resources you need in one simple view Deep insights into progress Immediate feedback for students Create custom assignments in just a few clicks. Practical teaching advice and ideas for each lesson provided in teachON Each lesson linked to the Key Knowledge (and Key Science Skills) from the VCE Chemistry Study Design Reading content and rich media including embedded videos and interactivities x ABOUT THIS RESOURCE powerful learning tool, learnON Teacher and student views Textbook questions Fully worked solutions and sample responses Practical investigation eLogbook Digital documents Video eLessons Interactivities Extra teaching support resources Interactive questions with immediate feedback ABOUT THIS RESOURCE xi Get the most from your online resources Online, these new Trusted Jacaranda theory, plus tools to support teaching and make learning editions are the more engaging, personalised and visible. complete package Each subtopic is linked to Key Knowledge (and Key Science Skills) from the VCE Chemistry Study Design. Interactive glossary terms help develop and support scientific literacy. onResources link to targeted digital resources including video eLessons and weblinks. Tables and images break down content, allowing students to understand complex concepts. Pink highlight boxes summarise key information and provide tips for VCE Chemistry success. xii ABOUT THIS RESOURCE Sample problems break down the process of answering questions using a think/write format and a supporting teacher-led video. Practical investigations are highlighted throughout topics, and are supported by teacher-led videos and downloadable student and teacher version eLogbooks. Online and offline question sets contain practice questions and past VCAA exam questions with exemplary responses and marking guides. Every question has immediate, corrective feedback to help students to overcome misconceptions as they occur and to study independently — in class and at home. ABOUT THIS RESOURCE xiii Topic reviews A summary flowchart shows the interrelationship between the main ideas of the topic. This includes links to both Key Knowledge and Key Science Skills. End-of-topic exam questions include past VCE exam questions and are supported by teacher-led videos. Area of Study reviews Areas of study reviews include practice examinations and practice SACs with worked solutions and sample responses. Teachers have access to customisable quarantined SACs with sample responses and marking rubrics. Practical investigation eLogbook Enhanced practical investigation support includes practical investigation videos and an eLogbook with fully customisable practical investigations — including teacher advice and risk assessments. xiv ABOUT THIS RESOURCE A wealth of teacher resources Enhanced teacher support resources, including: work programs and curriculum grids teaching advice additional activities teacher laboratory eLogbook, complete with solution and risk assessments quarantined topic tests (with solutions) quarantined SACs (with worked solutions and marking rubrics). Customise and assign A testmaker enables you to create custom tests from the complete bank of thousands of questions (including past VCAA exam questions). Reports and results Data analytics and instant reports provide data-driven insights into progress and performance within each lesson and across the entire course. Show students (and their parents or carers) their own assessment data in fine detail. You can filter their results to identify areas of strength and weakness. ABOUT THIS RESOURCE xv Acknowledgements The authors and publisher would like to thank the following copyright holders, organisations and individuals for their assistance and for permission to reproduce copyright material in this book. Selected extracts from the VCE Chemistry Study Design (2023–2027) are copyright Victorian Curriculum and Assessment Authority (VCAA), reproduced by permission. VCE® is a registered trademark of the VCAA. The VCAA does not endorse this product and makes no warranties regarding the correctness and accuracy of its content. To the extent permitted by law, the VCAA excludes all liability for any loss or damage suffered or incurred as a result of accessing, using or relying on the content. Current VCE Study Designs and related content can be accessed directly at www.vcaa.vic.edu.au. 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The three-minute story of 800,000 years of climate change with a sting in the tail, 2017. The Conversation: 592 © Source: Basin Salinity Management 2030, 2018–19 Comprehensive Report, 2020. Murray–Darling Basin Authority. Licensed under CC BY 4.0: 618 © Source: Clean water and ACKNOWLEDGEMENTS xvii sanitation, Monash Substainable Development Institute. Data from OECD: 376 © Source: Climate Action, Monash Substainable Development Institute. Data from Australian Department of Energy and Environment: 395 © Source: Life below water, Monash Substainable Development Institute. Data from Australian Institute of Marine Science (AIMS) Long-term Reef Monitoring Program: 378 © Source: Modified from Statistica/The Plastic Waste Makers Index. The Mindaroo Foundation: 343, 345 © Source: “Water For a Future Thriving Melbourne,” 2017, City West Water, South East Water, Yarra Valley Water, Melbourne Water: 373, 374 © R. 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Department of the Environment and Energy: 591 © Source: Department of Climate Change, Energy, the Environment and Water, https://www.awe.gov.au/environment/ protection/waste/publications/national-plastics-plan-summary: 362 © Source: Molar ionization energies of the elements, Wikipedia Commons. Retrieved from: https://en.wikipedia.org/wiki/Molar_ionization_energies_ of_the_elements#References. Licensed under Creative Commons Attribution-ShareAlike License 3.0: 222 Every effort has been made to trace the ownership of copyright material. Information that will enable the publisher to rectify any error or omission in subsequent reprints will be welcome. In such cases, please contact the Permissions Section of John Wiley & Sons Australia, Ltd. xviii ACKNOWLEDGEMENTS How can the diversity 1 UNIT of materials be explained? AREA OF STUDY 1 How do the chemical structures of materials explain their properties and reactions? OUTCOME 1 Explain how elements form carbon compounds, metallic lattices and ionic compounds, experimentally investigate and model the properties of different materials, and use chromatography to separate the components of mixtures. 1 Elements and the periodic table......................................................................................................................... 3 2 Covalent substances............................................................................................................................................ 59 3 Reactions of metals............................................................................................................................................ 113 4 Reactions of ionic compounds...................................................................................................................... 145 5 Separation and identification of the components of mixtures........................................................... 187 AREA OF STUDY 2 How are materials quantified and classified? OUTCOME 2 Calculate mole quantities, use systematic nomenclature to name organic compounds, explain how polymers can be designed for a purpose, and evaluate the consequences for human health and the environment of the production of organic materials and polymers. 6 Quantifying atoms and compounds............................................................................................................. 225 7 Families of organic compounds.....................................................................................................................259 8 Polymers and society........................................................................................................................................ 309 AREA OF STUDY 3 How can chemical principles be applied to create a more sustainable future? OUTCOME 3 Investigate and explain how chemical knowledge is used to create a more sustainable future in relation to the production or use of a selected material. 9 Research investigations..................................................................................................................... Source: VCE Chemistry Study Design (2023–2027) extracts © VCAA; reproduced by permission. AREA OF STUDY 1 HOW DO THE CHEMICAL STRUCTURES OF MATERIALS EXPLAIN THEIR PROPERTIES AND REACTIONS? Elements and the 1 periodic table KEY KNOWLEDGE In this topic you will investigate: Elements and the periodic table the definitions of elements, isotopes and ions, including appropriate notation: atomic number; mass number; and number of protons, neutrons and electrons the periodic table as an organisational tool to identify patterns and trends in, and relationships between, the structures (including shell and subshell electronic configurations and atomic radii) and properties (including electronegativity, first ionisation energy, metallic and non-metallic character and reactivity) of elements critical elements (for example, helium, phosphorus, rare-earth elements and post-transition metals and metalloids) and the importance of recycling processes for element recovery. Source: VCE Chemistry Study Design (2023–2027) extracts © VCAA; reproduced by permission. PRACTICAL WORK AND INVESTIGATIONS Practical work is a central component of VCE Chemistry. Experiments and investigations, supported by a practical investigation eLogbook and teacher-led videos, are included in this topic to provide opportunities to undertake investigations and communicate findings. EXAM PREPARATION Access exam-style questions and their video solutions in every lesson, to ensure you are ready. 1.1 Overview Hey students! Bring these pages to life online Watch Engage with Answer questions videos interactivities and check results Find all this and MORE in jacPLUS 1.1.1 Introduction Life is a mystery. Where did we come from? What are FIGURE 1.1 Everything in the universe that has we made of? Scientists tell us that we are made of very mass is composed of atoms. small particles called atoms and that these atoms have their origin in stars. What a remarkable journey these atoms must have undertaken while being recycled over the billions of years since the origin of the universe. All matter is made up of atoms. Every material thing that you can see, smell and touch, that occupies space and has mass, is a form of matter. Studying the structure and behaviour of matter — of which life, Earth and the universe are composed — has been ongoing. This topic introduces the fundamental structure and size of the building blocks of our universe, and how we have refined our theories to help us better understand our world. Atoms consist of even smaller subatomic particles and are amazingly 99.9 per cent empty space. There are 118 different atoms, known collectively as elements, which chemists organise into the periodic table. The periodic table is an indispensable tool, with remarkable patterns in its arrangement, that scientists use to predict the ways in which elements behave and react. LEARNING SEQUENCE 1.1 Overview.................................................................................................................................................................................................... 4 1.2 Elements.................................................................................................................................................................................................... 5 1.3 Electrons..................................................................................................................................................................................................12 1.4 The periodic table................................................................................................................................................................................ 25 1.5 Trends in the periodic table.............................................................................................................................................................. 32 1.6 Critical elements................................................................................................................................................................................... 43 1.7 Review...................................................................................................................................................................................................... 53 Resources Solutions Solutions — Topic 1 (sol-0800) Practical investigation eLogbook Practical investigation logbook — Topic 1 (elog-1606) Digital documents Key science skills (doc-37066) Key terms glossary — Topic 1 (doc-37067) Key idea summary — Topic 1 (doc-37068) Exam question booklet Exam question booklet — Topic 1 (eqb-0082) 4 Jacaranda Chemistry 1 VCE Units 1 & 2 Third Edition 1.2 Elements KEY KNOWLEDGE The definitions of elements, isotopes and ions, including appropriate notation: atomic number; mass number; and number of protons, neutrons and electrons Source: VCE Chemistry Study Design (2023–2027) extracts © VCAA; reproduced by permission. 1.2.1 The structure of atoms The atomic theory attempts to explain the structure of materials. FIGURE 1.2 A modern take on New According to this theory, all matter is made of atoms. Atoms Zealand–born Ernest Rutherford’s nuclear are so small that it was not until 1981 that their images could model of an atom. finally be seen using the newly invented scanning tunnelling microscope. Due to their incredibly small size, models have developed to represent the internal structure of atoms. One very useful model is the nuclear model of the atom proposed by Ernest Rutherford in 1911. Rutherford’s descriptions of an atom include: An atom is mostly empty space. An atom has a dense central structure called a nucleus. The nucleus, though its volume is very small relative to the atom as a whole, contains most of the mass of the atom. The nucleus is made up of positively charged particles called protons. The simplest nucleus is that of the hydrogen atom, which contains just one proton. All other atoms have nuclei that also contain neutrons. A neutron has no charge but has virtually the same mass as a proton. The empty space around the nucleus contains negatively charged particles called electrons. Electrons move very rapidly around the nucleus in orbits. atom a neutral particle with a Each electron has a definite energy and moves in a specific energy level. nucleus; the smallest constituent of an element The mass of an electron is very much less than that of a proton or a neutron. EXTENSION: Australia’s particle accelerator FIGURE 1.3 The Australian Synchrotron The Australian Synchrotron is a particle accelerator in Victoria that is used by scientists to investigate the structure of matter. With over 4000 research visits per year, the fields of investigation are diverse and include agricultural science, environmental science, minerals analysis, medical investigations, materials science, cultural heritage, nanotechnology and forensics. From the outside, the Australian Synchrotron resembles a football stadium. Inside, however, instead of footballs going in different directions, electrons are accelerated around a large loop (with a circumference of 216 metres) at almost the speed of light. The light is produced by high-energy electrons that are deflected into circular orbit by the ‘synchronised’ application of strong magnetic fields. The light produced is 1 million times brighter than the sun. The light, X-rays and infrared radiation produced is directed to a number of experimental workstations where many different experiments take place. TOPIC 1 Elements and the periodic table 5 Resources Video eLesson Rutherford’s gold foil experiment (eles-2486) Protons, electrons and neutrons are called subatomic particles. Figure 1.4 and table 1.1 summarise the properties of these particles. Atoms that are neutrally charged have the same number of electrons and protons. FIGURE 1.4 Subatomic particles in a nitrogen-14 atom Nucleus: 7 Electrons: 7 Protons – Electron – 2 Inner shell 7 Neutrons 5 Outer shell + Proton Neutron – – + + – + + – – – TABLE 1.1 Particles in an atom and their properties Subatomic particle Relative mass Relative charge Location 1 Electron = 0.0005 −1 Outside nucleus 1837 Proton 1 +1 In nucleus Neutron 1 0 In nucleus 1.2.2 Elements Atoms are not all the same. To date, chemists have identified 118 different types of atoms. Elements are substances that contain only one type of atom. For example, pure oxygen contains only oxygen atoms and pure lead contains only lead atoms. Elements subatomic particles particles in atoms: electrons, protons and are defined by the number of protons in the nucleus. neutrons The atoms of each element are classified based on the number of subatomic particles element a pure chemical species consisting of atoms of a single type they have. Very few elements exist as individual atoms; examples are helium and neon. Elements Elements are substances that contain only one type of atom. An element is defined by the number of protons in the nucleus. Atoms contain the subatomic particles protons, neutrons and electrons. 6 Jacaranda Chemistry 1 VCE Units 1 & 2 Third Edition 1.2.3 Atoms, elements, molecules and compounds Molecules are substances that consist of two or more atoms that are chemically combined. They contain either the same elements as in hydrogen gas, H2 , and oxygen gas, O2 , or different elements as in carbon dioxide, CO2 , and water, H2 O. Compounds are substances that contain two or more elements but not all compounds are molecules. Some elements (such as carbon, forming diamond and graphite) and compounds exist as continuous lattice structures, and these are discussed in topic 2. FIGURE 1.5 Elements, atoms, molecules and compounds Molecules Elements Compounds Atoms Molecule Molecule Compound (element) (compound) (not molecule) Molecules consist of two or more atoms chemically combined. FIGURE 1.6 Space-filling models of molecules of (a) carbon dioxide, CO2 , (b) water, H2 O, and (c) methane, CH4 Carbon dioxide, CO2 Water, H2O Methane, CH4 (a) (b) (c) 1.2.4 Representing elements Elements are represented by an element symbol, and with the atomic number and the mass number. Most symbols for elements come from the first letter or two letters of their names; for example, C for carbon and Cd for cadmium. Some atoms have symbols that have originated from a Greek or Latin name; for example, Au is the symbol for gold because gold was known in the past by its Latin name, aurum. Atomic number (symbol Z) molecule group of atoms bonded Each of the 118 elements known to chemists has its own atomic number. together covalently The atomic number (symbol Z) of an element is defined as the number of compound substance consisting of two or more elements protons in the nucleus of an atom of that element. symbol simplified representation When an atom is neutrally charged, the atomic number of the atom of an element consisting of one or corresponds to the number of electrons, because the number of positive two letters charges must be the same as the number of negative charges. For example, atomic number the number of protons in the nucleus of an atom oxygen has an atomic number of 8 and, therefore, has eight protons and of a particular element eight electrons. TOPIC 1 Elements and the periodic table 7 Mass number (symbol A) The mass number (symbol A) is defined as the total number of protons and neutrons in an atom of an element. Protons have approximately the same mass as neutrons. The electron’s mass is negligible compared with protons and neutrons. Therefore, the mass of an atom depends only on the number of particles in the nucleus. The elements are arranged in the periodic table in order of increasing atomic number. The relative atomic mass of each element is also shown on the table. Relative atomic mass is discussed in topic 7. Isotopic symbols An element is commonly represented as follows: mass number → A atomic number → Z E ← symbol for element This is known as the isotopic symbol of an element. We can determine the number of neutrons in an atom by subtracting the atomic number, Z, from the mass number, A. For example, sodium, Na, has atomic number 11 and mass number 23, and can be represented as 23 11 Na. An atom of sodium, therefore, has 11 protons and 12 neutrons. 1.2.5 Isotopes All atoms of a particular element contain the same number of protons and have the same atomic number. However, atoms of the same element can contain different numbers of neutrons, and these atoms are called isotopes. Isotopes have similar chemical properties because their electron structure is the same. They do, however, have different physical properties due to their different isotopic masses. Naturally occurring oxygen consists of three isotopes: 168 O , 178 O and 188 O. Isotopes are named by their element name followed by their mass number to distinguish them; for example, the isotopes of oxygen are oxygen-16, oxygen-17 and oxygen-18 (see figure 1.7). Aluminium has only one isotope, aluminium-27, 27 13 Al. FIGURE 1.7 Isotopes of oxygen – – – – – – – – – + + + – ++ ++ – ++ ++ – ++ ++ + + + ++ – ++ – ++ – – – – mass number the total number of protons and neutrons in the nucleus – – – of a particular isotope of an element – – – isotopic symbol representation of an element as AZ E , where E is the Oxygen-16 Oxygen-17 Oxygen-18 symbol for the element, A is the – 8 Electrons – 8 Electrons – 8 Electrons mass number and Z is the atomic number + 8 Protons + 8 Protons + 8 Protons isotopes forms of an element with 8 Neutrons 9 Neutrons 10 Neutrons the same number of protons but different numbers of neutrons in Mass number Mass number Mass number the nucleus = 8 + 8 = 16 = 8 + 9 = 17 = 8 + 10 = 18 8 Jacaranda Chemistry 1 VCE Units 1 & 2 Third Edition Isotopes FIGURE 1.8 The oldest reliably dated rock art in Australia is 28 000 years old. Isotopes are atoms of the same element that have different numbers of neutrons; that is, they have the same atomic number but different mass numbers. Isotopes can be used to date archaeological and geological features. Radiocarbon dating using the decay of carbon-14 isotopes is used to date organic material within (or nearby) Indigenous Australian rock art, for example. SAMPLE PROBLEM 1 Representing isotopes using appropriate notation tlvd-0509 a. Write the symbols for the atoms nitrogen-14 and nitrogen-15. b. How many protons does each atom have? c. How many neutrons does each atom have? d. What are these atoms called? e. Write the isotopic notation for each isotope of nitrogen. THINK WRITE a. The symbol will not change, regardless of the N atomic masses. b. The number of protons of an element will not 7 change, regardless of the atomic masses. The atomic number of N is 7, hence it has 7 protons. c. The number of neutrons can be determined nitrogen-14: using the following: 14 – 7 = 7 Number of neutrons = mass number (A) – nitrogen-15: atomic number (Z). 15 – 7 = 8 d. The name for atoms with the same number of Isotopes protons but with different masses (different number of neutrons). e. This must include the symbol, mass and nitrogen-14: 147 N atomic numbers in the correct format. nitrogen-15: 157 N PRACTICE PROBLEM 1 a. Write the elemental symbol for the atoms of hydrogen-1, hydrogen-2 and hydrogen-3. b. How many protons does each atom have? c. How many neutrons does each atom have? d. Write the isotopic notation for each species of hydrogen. TOPIC 1 Elements and the periodic table 9 1.2 Activities Students, these questions are even better in jacPLUS Receive immediate Access Track your feedback and access additional results and sample responses questions progress Find all this and MORE in jacPLUS 1.2 Quick quiz 1.2 Exercise 1.2 Exam questions 1.2 Exercise 1. MC An atomic particle has a net charge of zero and is found in the nucleus. Identify which type of particle it is. A. Proton B. Electron C. Neutron D. Positron 2. MC The particle that is represented by the symbol 121 Sb3+ has 51 A. 51 protons, 48 electrons and 121 neutrons. B. 51 protons, 48 electrons and 70 neutrons. C. 51 protons, 54 electrons and 121 neutrons. D. 51 protons, 54 electrons and 70 neutrons. 3. Look up your periodic table to find the atomic number of each of the following elements. a. H b. Ne c. Ag d. Au 4. An atom has 13 protons and 14 neutrons. Identify the following. a. Its atomic number b. Its mass number c. Its name 5. Find the symbols for elements with the following atomic numbers. a. 5 b. 12 c. 18 d. 20 6. In the element argon, Z = 18 and A = 40. For argon, state the following. a. The number of neutrons b. The number of electrons c. The isotopic symbol for this element 7. Determine the number of protons, neutrons and electrons in 7935 Br–. 8. An atomic nucleus consists of one proton and one neutron. What is its isotopic symbol? 10 Jacaranda Chemistry 1 VCE Units 1 & 2 Third Edition 9. a. Complete the following table. Element Number of protons Number of electrons Number of neutrons 12 6C 56 26 Fe 40 18 Ar 235 92 U 238 92 U 19 9 F b. Identify any isotopes in the table. c. Explain the difference between the isotopes. 10. Why do we identify an element by its atomic number rather than its mass number? 1.2 Exam questions Question 1 (1 mark) MC Which of the following species has a different number of neutrons from the rest? 64 A. 30 Zn 62 B. 28 Ni 63 C. 29 Cu 69 D. 31 Ga Question 2 (36 marks) Complete the following table. Atomic Mass Number of Number of Number of Name of Atom number number protons neutrons electrons element 23 11 Na 19 9 F 28 14 Si 56 26 Fe 197 79 Au 235 92 U Question 3 (2 marks) What is the general name for the group of atoms that includes carbon-12, carbon-13 and carbon-14? Identify the similarities and differences between these atoms. Question 4 (3 marks) The following isotopes belong to three elements. Identify the elements and list the isotopes next to the name of each element. 37 26 59 35 25 60 24 17 A 12 B 27 C 17 D 12 E 27 F 12 G Question 5 (1 mark) Tellurium is element 52 and iodine is element 53. Explain why iodine atoms have less mass than less than tellurium atoms. More exam questions are available in your learnON title. TOPIC 1 Elements and the periodic table 11 1.3 Electrons KEY KNOWLEDGE The structures (including shell and subshell electronic configurations and atomic radii) of elements The definitions of ions Source: Adapted from VCE Chemistry Study Design (2023–2027) extracts © VCAA; reproduced by permission. 1.3.1 Exciting electrons What causes rainbows? Why is it that when you look into a FIGURE 1.9 When wires with small fire you see different coloured flames? The answers lie in the amounts of different metal salts are placed way the electrons are arranged around the nucleus of the atom. in a flame, the electrons are excited and This arrangement largely determines the properties and the emit characteristic coloured light. behaviour of elements and the materials made from them. When white light is separated by a prism, a continuous spectrum of colour is observed. Every element emits light if it is heated by passing an electric discharge through its gas or vapour. This happens because the atoms of the element absorb energy and then lose it, emitting it as light. Passing the light emitted by an element through a prism produces an atomic Zinc Potassium Strontium Sodium Copper emission spectrum for that element. The emission spectra of elements are quite different from the spectrum of white light. White light gives a continuous spectrum, whereas atomic emission spectra consist of separate lines of coloured light. Each line in an emission spectrum corresponds to one particular frequency of light being given off by the atom; therefore, each line corresponds to an exact amount of energy being emitted. 1.3.2 Bohr’s energy levels In 1913, Niels Bohr suggested an explanation for the emission spectrum by FIGURE 1.10 The Bohr proposing a model for the hydrogen atom. His model proposed the following: model of an atom Electrons of specific energy move around the central nucleus in circular orbits or energy levels. Electrons cannot exist between these orbits. Electrons would not be found in Although an electron cannot lose energy while orbiting a nucleus, it can these ‘non-orbit’ areas. be given excess energy (by a flame or electric current) and then move to a higher orbit. If this happens, the electron has moved from the ground state 1st orbit (lowest energy level) to an excited state. Nucleus When an electron drops back down to a lower, more stable orbit, the excess energy is given out as a photon or quantum of light. This is seen as a line of 2nd orbit a particular colour on the visible spectrum. The energy given out is the difference in energy between the two energy 3rd orbit levels. Since only certain allowed energy levels are possible, the energy released has specific allowed values, each corresponding to a line in the atomic emission spectrum a emission spectrum. This spectrum is different for each element, so it is spectrum emitted as distinct bands of light of diagnostic frequencies by often called the ‘fingerprint’ by which an element may be identified. elements or compounds Some metallic elements can be identified simply by their characteristic flame colours ground state the least excited state of an atom, where the electrons when heated in a Bunsen burner flame. Copper burns with a blue–green flame, for are occupying the lowest possible example, and sodium burns with a yellow–orange flame. energy levels excited state raised to a higher than ground-state energy level photon particle of light 12 Jacaranda Chemistry 1 VCE Units 1 & 2 Third Edition FIGURE 1.11 White light is a continuous spectrum (top). The emission spectra of various atomic elements consist of distinct lines that correspond to differences in energy levels. λ 400 500 600 700 800 nm Li Na K Ca Sr Ba Emission spectra and electron energy levels When a particular amount of energy is supplied to an atom, an electron can move from a lower energy level to a higher energy level. When the electron returns to a lower state, it emits a photon of energy equal to the difference of energy between the two levels. Atomic emission spectra provide evidence that electrons exist in specific energy levels. FIGURE 1.12 Emission spectrum and energy levels; each electron transition produces a line of a different colour, with blue being the highest energy and shortest wavelength, 𝜆. λ 400 500 600 700 800 nm Blue–violet Blue–green Red n=6 n=5 n=5 n=4 n=3 e– n=4 Energy e– n=2 n=3 e– n=2 n=1 n=1 TOPIC 1 Elements and the periodic table 13 EXPERIMENT 1.1 elog-1662 Flame tests of metal cations tlvd-0614 Aim To observe the characteristic flame colours of the metal ions K+ , Na+ , Li+ , Sr2+ , Cu2+ , Ca2+ , Ba2+ , and to identify an unknown metal ion Resources Weblink Bohr model Electron shells Electrons may be visualised as moving within a region of space surrounding the nucleus. The regions are called electron shells and are numbered 1, 2, 3 and 4. A definite energy level is associated with each shell; the innermost shell (n = 1) has the lowest energy level. To move further away from the nucleus, an electron must gain energy. If it gains enough energy to completely leave the atom, the particle that is left is no longer neutral and is called a positive ion. Sodium, Na, has 11 protons and 11 electrons. If it loses an outer shell electron, it becomes the positive ion Na+ because it now has 11 protons and only 10 electrons. FIGURE 1.13 Sodium easily loses an outer shell electron to become a sodium ion. Na Na+ Further studies of line spectra in the 1910s and 1920s led to the prediction that a maximum number of electrons could be present in a given energy level. 1.3.3 Electron configuration The arrangement of electrons in the shells is called the atom’s electron configuration. The electron capacity of each shell is limited. The maximum number of electrons that each shell can hold is 2n2 where n is the shell number or energy level. Keep in mind the following when determining the electron configuration: Electron shells are filled in order from the nucleus, starting with the innermost shell, so that the electrons are in their lowest possible energy levels (or ground state). For example, the one electron of a hydrogen atom would be in the first shell, and the electron configuration is written as 1. Sodium has 11 electrons, so two go into the first shell, eight go in the second and the last electron goes in the third shell. The electron configuration of sodium, therefore, is written as 2, 8, 1. Chlorine has 17 electrons and an electron configuration of 2, 8, 7. Note that for the first 20 elements, the third shell never has more than eight electrons. Potassium, for example, has 19 electrons and an electron configuration electron configuration the arrangement of electrons in the of 2, 8, 8, 1 rather than 2, 8, 9. This means that the fourth shell is the outer shell shells of an atom for potassium electrons, rather than the third. 14 Jacaranda Chemistry 1 VCE Units 1 & 2 Third Edition Ions are atoms that have lost or gained one or more electrons. For example, a sodium atom has 11 electrons, so its electron configuration is 2, 8, 1. A sodium ion, Na+ , has lost an electron so its electron configuration is 2, 8. Chemists are particularly interested in the electrons in the highest energy level of an atom because it is these outershell electrons that mainly determine the chemical properties of elements. These electrons are called valence electrons. Valence electrons Valence electrons are the electrons in the outer shell of atoms. Shell model diagrams The electron configuration of an atom can be represented using shell model diagrams, such as those in figure 1.14. These show the electron shells as concentric rings around the nucleus, with the electrons marked on each ring, and help us to visualise the structure and behaviour of atoms. FIGURE 1.14 Shell model diagrams of hydrogen, sodium and chlorine; dots represent the electrons in the shells. int-0676 1p 11p 17p hydrogen sodium chlorine Limitations of the shell model The shell model represents only part of the story of the atom. More discoveries are always being made that cause scientists to reconsider their models and their understanding of the atom. The limitations of the shell model are as follows: The shell model doesn’t really explain the various differences in energies between the electron shells. It seems to imply that all the electrons orbit the nucleus in exactly circular paths, like planets around a sun. We know from looking at molecules with electron tunnelling microscopes that they come in many different shapes and sizes, so this model does not fully explain every aspect of every atom. The order of the electrons filling the electron shells is not really explained by this model either. For example, compare calcium (2, 8, 8, 2) with scandium (2, 8, 9, 2) — why isn’t the electron configuration of scandium 2, 8, 8, 3? Other models have been developed that are more complex and explain more of the data scientists have gathered. valence electrons electrons in 1.3.4 From atoms to ions the outermost shell of an atom; largely determine chemical Atoms gain or lose electrons to achieve more stable outer shell configurations; properties of an element and contribute to chemical bond they are then called ions. When an atom becomes an ion, it is no longer neutrally formation charged, since the number of electrons is not equal to the number of protons (see ion an atom that has lost or table 1.2). Note that the number of protons remains the same. An atom that gained electrons and so has has lost electrons becomes positively charged and is called a cation (e.g. Na+ ). a charge cation a positively charged ion An atom that has gained electrons becomes negatively charged and is called an anion a negatively charged ion anion (e.g. Cl– ). TOPIC 1 Elements and the periodic table 15 FIGURE 1.15 All elements in the periodic table are neutral but some can become charged when they gain or lose electrons. loss of gain of electron(s) neutral electron(s) atom cation anion TABLE 1.2 Common atoms and their ions Atom/ion Symbol Number of protons Number of electrons Sodium atom Na 11 11 + Sodium cation Na 11 10 Chlorine atom Cl 17 17 Chloride anion Cl– 17 18 Ions Ions are formed when an atom gains or loses electrons; in other words, the atom becomes charged. Metallic ion formation The metallic elements are those on the left side of the mauve staircase in figure 1.16 (except hydrogen). Metals tend to lose electrons to achieve a noble gas configuration in their outer shells. FIGURE 1.16 Periodic table (up to element 89) showing the division between metals and non-metals Group Group Group Group Group Group Group Group 1 2 13 14 15 16 17 18 1 2 Period 1 Non-metals H He 3 4 5 6 7 8 9 10 Period 2 Li Be B C N O F Ne 11 12 13 14 15 16 17 18 Period 3 Na Mg Al Si P S Cl Ar 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Period 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Period 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Period 6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 87 88 89 Period 7 Fr Ra Ac Note: Numbers are used to identify periods and groups. Roman numerals are no longer used. 16 Jacaranda Chemistry 1 VCE Units 1 & 2 Third Edition For example, lithium is a very reactive group 1 metal with one outer shell electron and the electron configuration 2, 1. In order to obtain the stable configuration of a full outer shell, the lone electron is lost (see figure 1.17). The electron configuration, 2, of the nearest noble gas, helium, results. Since the lithium cation has three protons but only two electrons, it has a net charge of +1. Charges are written as superscripts above and to the right of the element symbol; thus the lithium atom is now written as Li+. This process can be represented by electron shell diagrams or in the simple equation form in figure 1.17. FIGURE 1.17 The lithium atom has one valence electron, which it loses to form the lithium cation, which has a charge of +1. Li Li+ + e− lithium atom lithium ion + one electron Li Li+ + e– 2, 1 2 Note: When an atom’s net charge is +1 or −1, it is not necessary to include the numeral 1 in the superscript notation. Consider the following groups and periods: The group 2 and group 13 metals contain two and three valence electrons respectively. They lose their outer shell electrons to form ions with charges of +2 and +3 respectively. The periods 2, 3 and 4 form simple ions with electron configurations identical to those of the closest noble gases. Each occupied energy shell contains the maximum number of electrons. Examples of their electron configurations are as follows: Li+ 2 + Na 2, 8 + K 2, 8, 8. When we name a metallic ion, we use the full name of the metal followed by the word ‘ion’ to distinguish it from the uncharged metal. Note: The group 14 elements, carbon and silicon, do not form simple ions. Metal ions Metals form positive ions. Non-metallic ion formation Non-metallic elements are shown on the right side in the purple section of the periodic table in figure 1.16. They gain electrons to achieve a noble gas configuration of eight electrons in their outer shells (except for hydrogen). For example, oxygen in group 16 has six outershell electrons and has the electron configuration 2, 6. It is too difficult to remove all six electrons to achieve a full outer shell, so the oxygen atom gains two electrons instead to become a stable anion, O2− , as shown in figure 1.18 and the simple equation. TOPIC 1 Elements and the periodic table 17 FIGURE 1.18 The oxygen atom has six valence electrons, and gains two electrons to form the oxide ion, which has a charge of −2. O + 2e− O2− oxygen atom + two electrons oxide ion O + 2e− O2– 2, 6 + 2e− 2, 8 An anion has more electrons than a neutral atom of the same element; here, the oxygen ion has eight protons and ten electrons, resulting in a net charge of −2. The electron configuration of the oxygen anion is now that of a neon atom: 2, 8. The oxygen atom has become an oxide ion. (It is a convention in chemistry to indicate the ions of non-metallic elements with the suffix -ide.) Non-metal ions Non-metals form negative ions. SAMPLE PROBLEM 2 Identifying the ions formed from atoms tlvd-0515 Write the symbol, charge and name of the ions you would expect atoms of the following elements to form. a. Mg b. S THINK WRITE a. Mg is a metal found in group 2. It has the simplified Mg2+ electron configuration 2, 8, 2. In order to become magnesium ion stable, the Mg atom needs to lose two electrons. The charge of the resultant ion would, therefore, be +2. b. S is a non-metal found in group 16. It has the S2– simplified electron configuration 2, 8, 6. In order to sulfide ion
