Pure Chem S3 Notes (BT 2019) Final Update 23 July 2021

Pure Chemistry Notes 1 PURE CHEMISTRY NOTES 2021 ©

Pure Chemistry Notes 2

Pure Chemistry Notes 3 3EXP CHEMISTRY TOPICS No. Topics Page Remarks 1 Atomic Structure 4 2 Chemical Formula 8 3 Balancing equations 11 4 State Symbols 12 5 Element, Mixtures and Compounds 14 6 Experimental Techniques & Measurement 17 7 Separation Techniques 24 8 Kinetic Particle Theory 33 9 Chemical Bonding – Ionic 39 10 Chemical Bonding - Covalent 42 11 Acids and Their Reactions 47 12 Alkalis and Their Reactions 53 13 Types of Oxides 63 14 Salt Solubility 66 15 Salt Preparation 67 16 Metals – Properties of Metals 78 17 Metals – Reactivity of Metals 82 18 Metals - Extraction 93 19 Metals – Rusting and Prevention 98 20 Mole Concept 103 23 Definition List 132 24 Colours of Common Substances 142

Pure Chemistry Notes 4 ATOMIC STRUCTURE Atoms are the smallest particles an element can exists. They are electrically NEUTRAL (which means they have equal number of protons and electrons) They consist of: (a) Nucleus where protons (+) and neutrons (no charge) are found and; (b) Electron shells where electrons (-) are found. When the number of electrons and protons are not equal, the atom is no longer electrically neutral. It has become a: (a) Positively charged ION (More protons than electrons) → Cation, X+ (b) Negatively charged ION (Less protons than electrons) → Anion, Y- IONS – Charged Atoms To obtain a stable noble gas structure, atoms have to: (a) Give away electrons → form Positive (+) ions (b) Take in electrons → form Negative (-) ions Al atom (2.8.3) Al3+ ion (2.8) 3+ Al Al 2- O O O atom (2.6) O2- ion (2.8) 3 negative electrons are lost 2 negative electrons are taken in 3 negative electrons are lost. The number of protons do not change. There are 13 Protons and 10 electrons. Hence overall is +3 2 negative electrons are taken in. There are now 10 electron and 8 protons. Hence the overall is -2

Pure Chemistry Notes 5 Particles Location Charge Mass Remarks Proton Nucleus +1 1 unit Protons and neutrons in the nucleus of an atom are collectively known as NUCLEONS Neutron Nucleus No charge 1 unit Electron Electron shell -1 1/1840 ISOTOPES Definition: Isotopes are atoms of the same element with the same number of protons and electrons but different number of neutrons. Hence isotopes have the same: (a) Number of protons and electrons (b) Chemical properties due to similar electronic configuration But they have different: (a) Number of neutrons (b) Physical properties like mass, density Common Isotopes are: 25% of isotopes of Chlorine are 37-Cl and 75% of isotopes of Chlorine are 35-Cl Hence the average mass of Chlorine is calculated as shown: Relative atomic mass of Chlorine = 25% x 37 + 75% x 35 = 35.5 Hence Chlorine in the Periodic Table is Other Isotopes are: 𝐶𝑙37 17 𝐶𝑙35 17