UNIT 1 CHEMISTRY BOOK 1

Transcription

1 UNIT 1 CHEMISTRY BOOK 1 How Can the Diversity of Materials Be Explained? Page 1 AoS 1: How Can the Knowledge of Elements Explain the Properties of Matter? Page 1 AoS 2: How Can the Versatility of Non-Metals be Explained? Page 1 AoS 3: Research Investigation Page 2 States of Matter Page 3 Physical Classification of Matter Page 3 Chemical Classification of Matter Page 4 Relative and Absolute Sizes of Particles Page 6 Atoms and their Structure Page 7 Elements and Compounds Page 8 Elements Page 8 Atomic Elements Page 8 Molecular Elements Page 9 Elemental Lattices Page 9 Compounds Page 10 Molecular Compounds Page 10 Macromolecules Page 10 Ionic Compounds Page 10 Defining Atoms Page 11 Atomic Nuclei Page 11 Electron Arrangement Page 11 Atomic Number Page 13 Mass Number Page 13 Isotopic Symbols Page 13 Isotopes Page 16 Electron Configuration Page 18 Shells Page 19 Subshells Page 20 Orbitals Page 21 Shapes of Orbitals Page 23 Filling Orbitals Page 24 Electron Configuration Exceptions Page 30 Electron Configuration of Ions Page 31 Anions Page 31 Cations Page 31

2 Evidence for Energy Levels Page 37 Emission Spectra Page 37 Electron Configurations of Atoms in Excited States Page 43 Ionisation Energies Page 45 Development of Atomic Theory Page 50 The Modern Periodic Table Page 57 A Periodic Table of the Elements Page 58 Groups Page 59 Periods Page 61 Blocks Page 61 Trends in the Periodic Table Page 66 The Shielding Effect Page 66 Effective Nuclear Charge Page 68 Effective Nuclear Charge Across Periods Page 68 Effective Nuclear Charge Down Periods Page 69 Trends in Atomic Radii Page 70 Trends Across a Period Page 70 Trends in Metallic Nature Page 71 Trends Across a Period Page 71 Trends Down a Group Page 71 Trends in Electronegativity Page 72 Trends Across a Period Page 72 Trends Down a Group Page 73 Other Trends in the Periodic Table Page 78 Trends in Reactivity Page 78 Patterns in Compounds Page 80 Patterns in Oxides Page 81 Patterns in Hydrides Page 83 Summary of Trends Page 84 Development of the Periodic Table Page 85 Materials Page 89 Chemical Bonding Page 89 Metals Page 90 Properties of Metals Page 90

3 Metallic Structure Page 91 Metallic Bonding Model Page 92 Explaining Metal Properties Page 94 Electrical Conductivity Page 94 Heat Conductivity Page 94 Lustre Page 95 Melting Points and Boiling Points Page 95 Malleability and Ductility Page 96 Hardness Page 96 Density Page 96 Comparing Metal Properties Page 99 Properties of the S-Block Metals Page 99 Properties of the P-Block Metals Page 99 Transition Metals (D-Block Metals) Page 101 Properties of the D-Block Metals Page 102 Limitation of the Metallic Bonding Model Page 104 Modifying Metals to Make Them More Useful Page 104 Alloying Page 106 Work Hardening Page 109 Heat Treatment Page 109 Metallic Coatings Page 110 Metal Fatigue Page 111 Reactivity of Metals Page 113 Reactions of the Metals Page 113 Reactivity Series of Metals Page 114 Extraction of Metals Page 116 Extraction of Iron Page 116 Environmental Impacts Page 118 Economic Impacts Page 118 Nanometals Page 121 Applications Page 121 Unique Nanometal Properties Page 122 Solutions

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5 UNIT 1 CHEMISTRY HOW CAN THE DIVERSITY OF MATERIALS BE EXPLAINED? Unit 1 has three Areas of Study (AoS): AoS 1: HOW CAN KNOWLEDGE OF ELEMENTS EXPLAIN THE PROPERTIES OF MATTER? In this area of study students focus on the nature of chemical elements, their atomic structure and their place in the periodic table. They review how the model of the atom has changed over time and consider how spectral evidence led to the Bohr model and subsequently to the Schrödinger model. Students examine the periodic table as a unifying framework into which elements are placed based upon similarities in their electronic configurations. In this context students explore patterns and trends of, and relationships between, elements with reference to properties of the elements including their chemical reactivity. Students investigate the nature of metals and their properties, including metallic nanomaterials. They investigate how a metal is extracted from its ore and how the properties of metals may be modified for a particular use. Students apply their knowledge of the electronic structures of metallic elements and non-metallic elements to examine ionic compounds. They study how ionic compounds are formed, explore their crystalline structures and investigate how changing environmental conditions may change their properties. Fundamental quantitative aspects of chemistry are introduced including the mole concept, relative atomic mass, percentage abundance and composition by mass and the empirical formula of an ionic compound. Source: VCAA Chemistry Study Design AoS 2: HOW CAN THE VERSATILITY OF NON-METALS BE EXPLAINED? In this area of study students explore a wide range of substances and materials made from non-metals including molecular substances, covalent lattices, carbon nanomaterials, organic compounds and polymers. Students investigate the relationship between the electronic configurations of non-metallic atoms and the resultant structures and properties of a range of molecular substances and covalent lattices. They compare how the structures of these non-metallic substances are represented and analyse the limitations of these representations. Students study a variety of organic compounds and how they are grouped into distinct chemical families. They apply rules of systematic nomenclature to each of these chemical families. Students investigate useful materials that are made from non-metals, and relate their properties and uses to their structures. They explore the modification of polymers and the use of carbon-based nanoparticles for specific applications. Students apply quantitative concepts to molecular compounds, including mole concept and percentage composition by mass, and determine the empirical and molecular formulas of given compounds. Source: VCAA Chemistry Study Design The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 1

6 AoS 3: RESEARCH INVESTIGATION In this area of study students apply and extend their knowledge and skills developed in Area of Study 1 and/or Area of Study 2 to investigate a selected question related to materials. They apply critical and creative thinking skills, science inquiry skills and communication skills to conduct and present the findings of an independent investigation into one aspect of the discoveries and research that have underpinned the development, use and modification of useful materials or chemicals. Students undertake a research investigation relevant to one of the following ten options. A question from the list under each option may be selected or students may develop their own research question relevant to Area of Study 1 and/or Area of Study 2 in conjunction with their teacher. For the selected question, students outline, analyse and evaluate relevant evidence to support their conclusions. Source: VCAA Chemistry Study Design The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 2

7 STATES OF MATTER PHYSICAL CLASSIFICATION OF MATTER The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 3

8 CHEMICAL CLASSIFICATION OF MATTER Matter Pure Substance Impure Substance Elements Compounds Homologous Mixture Uniform composition throughout the substance. Heterogeneous Mixture Variable composition throughout the substance. Metals Molecular Ionic Salty water Soil Non-metals Polar Anions Air Cake Metalloids Non-polar Cations Noble Gases Atoms of an element. Molecules of an element. Molecules of a compound. Mixture of elements and a compound. The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 4

9 QUESTION 1 Classify the following as either: i. A mixture or pure substance ii. Element or compound (or both) Solution 1. A: Pure substance, compound 2. B: Mixture of two elements 3. C: Mixture of a compound and an element 4. D: Pure substance, compound 5. E: Pure substance, element 6. F: Pure substance, element 7. G: Mixture of two compounds 8. H: Pure substance, element 9. I: Pure substance, compound The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 5

10 RELATIVE AND ABSOLUTE SIZES OF PARTICLES Throughout the course of human history, our ability to manipulate our environment has increased as technology has allowed us to work on ever larger and smaller scales. For thousands of years, humans worked with materials that were easily manipulated by hand. This placed a limit on how small or large tools and objects could be before they became too difficult to manage. The use of horses helped to increase the magnitude of human construction as did the invention of the wheel and the use of inclined planes. In more recent times, the use of machines has increased the scale to which we can manipulate objects. Working with objects on a smaller scale was only made possible with the invention of the microscope. The smallest objects that can be seen by the human eye are about the width of a human hair (0.05 mm). The microscope allowed for the manipulation of materials on the micro-scale (micrometres one millionth of a metre, or 10 6 metre, or 1 μm). This lead to the development of new technologies such as microelectronics and microsurgery. Microelectronic circuits dramatically improved performance, functionality, and reliability of electronic devices which led to the Information Revolution. The rise of nanotechnology has further decreased the size of objects that we can manipulate. Nanotechnology refers to a field of applied science where matter is controlled on an atomic and molecular scale. Relative Size of Objects 1 nanometer (nm) = 10-9 metre, or one billionth of a metre. Object Size (nm) Proton 10-6 Nucleus of a gold atom 1.4 x 10-5 Large atom 0.1 Hydrogen Molecule 0.15 Water Molecule 0.1 Germ 1,000 Hair 100,000 Shaquille O Neal (basketballer) 2,160,000,000 Source: Chemwiki The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 6

11 ATOMS AND THEIR STRUCTURE All matter is made up of tiny particles known as atoms. Atoms are so small that even the most powerful microscopes cannot give detailed pictures of the internal structure of atoms. Therefore, most of what we know about atoms has come from theoretical models and indirect observations. An atomic model represents what the structure of an atom could look like, based on what we know about how atoms behave. Atomic model theories have developed over the years and are the result of one scientist building on the ideas of others. These ideas collectively led to the development of the current atomic model (the Quantum Mechanical Model ), which was proposed by Erwin Schrodinger and Werner Heisenberg in The idea of atoms was first proposed by two Greek philosophers, Democritus and Leucippus in 450 B.C. They suggested that all matter was made up of tiny, invisible particles (atoms) that could not be broken down into smaller pieces. Nowadays, we know that atoms are made up of smaller units called subatomic particles, namely protons, neutrons and electrons. The positively charged protons and the neutrons (neutral) are contained in a dense positively charged nucleus, which is located in the centre of the atom. The negatively charged electrons are found in electron clouds which surround the nucleus, and take up most of the space occupied by atoms. Subatomic Particle Location Charge Proton Nucleus Positive Electron Electron clouds around the nucleus Negative Neutrons Nucleus Neutral The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 7

12 ELEMENTS & COMPOUNDS ELEMENTS An element: Is a substance that contains only one type of atom. Is a substance that cannot be broken down into simpler substances by chemical means. Is composed of atoms that have the same atomic number (i.e. have the same number of protons). Of the 118 known elements, 92 occur in nature, while the remainder have only been made with particle accelerators. Eighty-one of the elements have isotopes that are stable. The others, including technetium, promethium, and those with atomic numbers higher than 83, are radioactive. Very few elements exist as individual atoms. Those that do exist as atoms belong to Group 18 (Noble gases) of the periodic table. The other elements exist in a variety of forms in order to achieve a stable arrangement of electrons. Atomic Elements Group 18 elements (He, Ne, Ar, Xe, Rn...) Elements in Group 18 already have a stable electron configuration and are found in an atomic form. The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 8

13 Molecular Elements Non-metal atoms which do not belong to Group 18 of the periodic table can bond together in small groups in order to gain maximum stability. The molecular formula reflects the actual number of atoms in the molecule. Fluorine exists as a diatomic molecule with the molecular formula F 2. Elemental Lattices Some elements (metals and non-metals) can bond together in giant lattices in order to achieve maximum stability. The formula of these lattices is given by the symbol of the element. Chemical Formula: C diamond Elemental carbon has a number of forms. One is the giant 3D lattice structure found in diamond. Metals are also found as large 3D lattices in their elemental form. Chemical Formula: Na The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 9

14 COMPOUNDS A compound is a substance that contains two or more types of atom chemically bonded to each other. Compounds form so that atoms can achieve a stable arrangement of electrons. Molecular Compounds A molecular compound is a small group of two or more non-metal atoms chemically bonded together as a discrete group. The molecular formula reflects the actual number and type of atoms in the molecule. Macromolecules Macromolecules are very large molecules which contain thousands of non-metal atoms. They can be made by joining many small molecules together. If the molecule is made in this way, then the molecular formula will indicate the smallest repeating unit found in the molecule. Polyethene forms large molecules. Its molecular formula is (CH 2 ) n. Ionic Compounds Metallic elements can combine with non-metallic elements to form ionic compounds. When existing as solids, ionic compounds will form ionic lattices. The ionic formula indicates the lowest whole number ratio of atoms in the compound. Ionic Formula: NaCl The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 10

15 DEFINING ATOMS All matter is made up of atoms which are unimaginably small. The radius of an atom falls in the order of m. Most of an atom consists of empty space. In an atom, the number of protons is equal to the number of electrons. This makes atoms electrically neutral. In some atoms, the number of neutrons is about the same as the number of electrons/protons, but this is not always the case. Hydrogen is the only atom that contains no neutrons. ATOMIC NUCLEI The protons and neutrons are found in the nucleus of the atom. They have roughly the same mass and are assigned a relative value of 1. They give the atoms its mass. Electrons basically have no mass (they are about 1/1837 the mass of a neutron or proton). ELECTRON ARRANGEMENT Electrons are arranged in shells around the nucleus. These shells are also known as energy levels. Only two electrons can fit into the first shell (the one nearest the nucleus) but eight can fit into the second shell and 18 can fit into the third shell. However, whichever shell is the outer shell will only hold eight even if it is capable of holding more. NOTE: The maximum number of electrons that can fit into a shell at any one time can be calculated using the expression 2n 2, where n = the number of the shell. Instead of always drawing atoms to indicate the number of electrons in each shell, we can write an electron configuration. The electron configuration for the sodium atom (which has 11 electrons) for example, is 2 8 1, showing that there are two electrons in the first shell, eight in the second and one in the third. The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 11

16 QUESTION 2 Complete the following table. Element Number of Electrons Electron Configuration He 2 Cl 17 Ca 20 N 7 QUESTION 3 Compare and contrast the mass, charge and location of the proton, neutron and electron in the atom. Solution The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 12

17 ATOMIC NUMBER The atomic number (Z) of an atom is equal to the number of protons it contains. All atoms of a particular element have the same number of protons, hence, atomic numbers are used to identify atoms. MASS NUMBER The mass number (A) of an atom is equal to the number of protons and neutrons in an atom. The mass number is given its name since the mass of protons and neutrons is so much larger than the mass of electrons that they make up almost the entire mass of an atom. ISOTOPIC SYMBOLS Combining the mass number and atomic number with the symbol of an element provides a lot of useful information about that element. A Z X massnumber atomicnumber X Where: X represents the element s symbol. A represents the mass number (the total number of protons and neutrons in an atom s nucleus). Z represents the atomic number (the number of protons in an atom s nucleus). Useful information from an isotopic symbol: The symbol can be used to identify the element. The atomic number can be used: To find the element on the periodic table. To determine the number of protons in an atom. To determine the number of electrons in a neutral atom. To determine the number of neutrons in an atom (in conjunction with the mass number). The mass number can be used to determine the number of neutrons. The number of neutrons = Mass number Atomic number EXAMPLE The notation Cl indicates that each atom of this isotope contains: 17 protons 18 neutrons 17 electrons The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 13

18 QUESTION 4 Complete the following table: Atomic Number Name of Isotope Chemical Symbol Number of Protons Number of Neutrons Number of Electrons Mass Number of Isotope 5 Boron S Lead QUESTION 5 Write down the number of protons, electrons and neutrons in Cl. Solution QUESTION 6 Which of the following particles contain more electrons than neutrons? I II III A B C D 1 H Cl K+ I only II only I and II only II and III only The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 14

19 QUESTION 7 The atom with the same number of neutrons as 54 Cr is: A B C D 50 Ti 51 V 53 Fe 55 Mn QUESTION 8 The nucleus of a tritium atom, 3 1 H, contains: A B C D Two neutrons and one proton Three neutrons Two protons and one neutron Three protons QUESTION 9 Which species contains 16 protons, 17 neutrons and 18 electrons? A 32 S - B 33 S 2- C 34 S - D 35 S 2- QUESTION 10 Why is the identity of an atom determined by the number of protons it has rather than by the number of electrons or neutrons? Solution The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 15

20 ISOTOPES Two neutral atoms of the same element will always have the same number of protons and electrons as each other. However, they may have a different number of neutrons. E.g. Complete the following table. Isotope No. of protons No. of electrons No. of neutrons 12 6 C 13 6 C Both of these forms of carbon are known as isotopes. Since all of the isotopes of an element have the same electron configuration, they will also have the same chemical properties (i.e. they react in the same way). This is because it is the electron arrangement of an atom that determines its chemical properties. However, the physical properties such as the mass of the isotope, density and boiling point will be different. Hydrogen s three most common isotopes are: 1 1 H, 2 1 H and 3 1 H. Carbon s two most common isotopes are C and C. 6 Chlorine s isotopes are Cl and Cl. 17 QUESTION 11 Oxygen consists of three different isotopes: O, 8 O and O (a) What are isotopes? (b) Would you expect oxygen s three isotopes to have the same chemical properties? Give a reason for your answer. The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 16

21 QUESTION 12 Carbon consists of three different isotopes with masses of 12, 13 and 14. If each carbon atom contains 6 protons, express each isotope in A - Z notation. Solution QUESTION 13 Which of the following sets represents a pair of isotopes? A 14 6 C and 14 7 N B O 2 and O 3 C D S and 16 S Pb and Pb 82 QUESTION 14 The atomic and mass numbers for four different nuclei are given in the table below. Which two are isotopes? Atomic number Mass number I II III IV A B C D I and II II and III II and IV III and IV Solution The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 17

22 ELECTRON CONFIGURATION In 1913, Neil s Bohr suggested that electrons orbit the nucleus in distinct orbits that each have a specific energy value. The orbit closest to the nucleus is lowest in energy and as the orbits move further away from the nucleus, their energy value increases. The electrons exhibit the same energy as the energy of the orbit they are in. These orbits are also known as energy levels. Bohr stated that electrons could not exist between these energy levels but could move between them. Although the current model of the atom includes the concept of energy levels, the idea of electrons orbiting the nucleus is not accurate. They actually occupy regions of space called orbitals. Note: Although atoms are not found in spherical regions of space around the nucleus, this model is used to help visualise how the energy levels are organised. The School For Excellence 2016 Unit 1 Master Classes Chemistry Book 1 Page 18