Queen's University APSC 131 - Chemistry of Materials Lecture 02 - Atomic Basics PDF

APSC 131 – Chemistry of Materials Lecture 02 – Atomic Basics Learning Plan Keywords Resources Atomic number, atomic mass, the mole, and APSC 131 OnQ Page abundance Electronegativity, ionization energy, ionic Course Syllabus...

APSC 131 – Chemistry of Materials Lecture 02 – Atomic Basics Learning Plan Keywords Resources Atomic number, atomic mass, the mole, and APSC 131 OnQ Page abundance Electronegativity, ionization energy, ionic Course Syllabus charge, atomic radius Learning Outcomes Quantify mass, composition, and charge of atoms/isotopes/ions Connect electronegativity, ionization energy, ionic charge, and atomic radius Identify periodic trends in atomic structure and properties 2 Verifying Food Quality: Carbon Isotopes of Honey Naturally occurring honey is valuable (and delicious), but supply is limited by the productivity of bees To raise profits, some manufacturers dilute their honey with cheaper sources of sugar (e.g., corn syrup) However, the ratio of 13C to 12C in naturally occurring honey sugars is measurably different from that of other sugars Thus, if we can measure this ratio, we can Source: https://hunaja.fi/en/about-honey/ determine whether a sample of honey is pure 3 4 Navigating the Periodic Table – Regions The modern Periodic Table is defined based on atomic number and can be described in terms of periods, groups, or regions. Elements are frequently grouped into four main regions: Main Group Metals Transition Metals Metalloids Non-metals These categories are defined by similar P Duchesne, 2023 chemical properties. 5 Navigating the Periodic Table – Groups Elements within a group tend to share similar chemical (and some physical) properties: Electron Configuration Electronegativity Ionization Energy Ionic Charge Electrical Conductivity P Duchesne, 2023 6 Navigating the Periodic Table – Periods The period’s number corresponds to the principal quantum number for the electronic orbitals of its atoms (e.g., 3s2). Elements in each successive period tend to exhibit more metallic character (see Groups 13 through 16). We will discuss other trends in detail during the next lecture. P Duchesne, 2023 7 Navigating the Periodic Table Provide the name and chemical symbol for each of the following: 1) A non-metal in the second period 2) A Group 1 element 3) A third-period, Group 17 element 4) An element that is a gas at 0 °C and 1 bar pressure https://www.mathtutordvd.com/public/Periodic-Table-Larger-Version.cfm 8 Elemental Symbols Elemental symbols may include additional information, indicated by numbers in specific locations: n Upper left: Mass number (𝒎𝒊 ) Total number of protons and neutrons in an atom Upper right: Ionic charge (𝒒) Net electric charge on an atom Lower left: Atomic number (𝒁) Equal to number of protons in atom Manganese Lower right: Number of atoms (𝑵) Number of atoms in a molecule or formula 9 Identifying Isotopes Your engineering team is designing the solar reflector used to light the Olympic flame. Your team selects silver for the reflective surface. The elemental symbol of the silver supplied for the project is 107 Ag. Determine the number of neutrons in the silver atoms used in the mirror. Report the average number of neutrons in a silver atom (using atomic mass from the periodic table). Source: https://www.mathtutordvd.com/public/Periodic-Table-Larger- Version.cfm 10 Blank Slide for Notes Isotopic Abundance and Average Atomic Mass The atomic mass reported by the periodic table Isotopes of Molybdenum (in amu) is a weighted average of the masses for 𝑚average = 95.95 amu each stable isotopes (𝑚𝑖 ). The abundance (𝐴) of Isotope Mass (amu) Relative Abundance (%) each isotope provides the basis for the 91.9 14.6 weighting. 93.9 9.2 94.9 15.9 𝑚average = ෍ 𝑚𝑖 𝐴𝑖 95.9 16.7 𝑖 96.9 9.6 An element may have many isotopes that are not 97.9 24.3 stable which have lesser if any influence on the 100 9.7 average mass. 12 Isotopic Abundance and Average Atomic Mass Identify the element corresponding to the isotopes reported in the table below. Isotope Mass (amu) Relative Abundance (%) 123.9 0.1 125.9 0.1 127.9 1.9 128.9 26.4 129.9 4.1 130.9 21.2 131.9 26.9 133.9 10.4 135.9 8.9 13 Blank Slide for Notes Quantifying Matter – The Mole The amount of a substance (𝑛) is quantified in moles (mol), where: 1 mol = 6.022 × 1023 somethings These “somethings” may be atoms, molecules, or other particles. The number of somethings contained in one mole is known as Avogadro’s number: 𝑁A = 6.022 × 1023 mol−1 The amount of substance (in moles) is equal to its mass (𝑚) divided by its molecular mass (𝑀): 𝑚 (g) 𝑛 (mol) = g 𝑀 mol An atomic mass unit is equivalent to the number of grams in a single mole of that element. 1 amu = 1 gΤmol 15 Molar Mass Your silver mirror is accidentally exposed to nitric acid. You find that 10 g of silver nitrate (AgNO3 ) are formed as a result of the exposure. Report the mass (in grams) of silver that has reacted. Determine if it is expensive to replace the lost silver if 1 gram of silver costs 1.29 CAD. Source: https://www.mathtutordvd.com/public/Periodic-Table-Larger- Version.cfm 16 Blank Slide for Notes Quantifying Matter – Concentration Concentration describes the amount of a substance per unit volume of a mixture (gas, liquid, or solid) Molar concentration (𝑐) (or “molarity”) describes the number of moles (𝑛) of a substance (𝑖) that are contained in given volume of solution (𝑉soln ): 𝑛𝑖 𝑐𝑖 = 𝑉soln Moles-per-litre (molΤL) is also expressed using molarity units (M) Molarity is primarily used to describe liquid mixtures Source: https://i.gifer.com/HfL1.mp4 18 Quantifying Matter – Mass, Mole, and Volume Fractions 𝑚𝑖 Mass fraction (𝑤𝑖 ) describes the mass of a substance (𝑖) per unit 𝑤𝑖 = 𝑚total mass of a mixture (gas, liquid, or solid) 𝑛𝑖 Mole fraction (𝑥𝑖 ) describes the amount of a substance (𝑖) per unit 𝑥𝑖 = 𝑛total mole of a mixture (gas, liquid, or solid) 𝑉𝑖 Volume fraction (𝜑𝑖 ) describes the volume of a substance (𝑖) per 𝜑𝑖 = unit volume of a mixture (gas, liquid, or solid) 𝑉total Volume fraction is not as common as the other fractions, as volume is not always additive in mixtures 19 Ions – Atoms with Electric Charge Ions form when atoms gain or lose electrons: Electron gains or loses depend on elemental chemical properties (ionization energy and electronegativity) Net ionic charge (𝑞) becomes More negative when electrons are gained More positive when electrons are lost Positively charged ions are called cations − Cl Cl Negatively charged ions are called anions Source: https://d20khd7ddkh5ls.cloudfront.net/chlorine_vs_chloride.jpeg 20 Ions in Solution Soft drink quality is determined by the concentration of hydrogen ions dissolved in the beverage. This is also known as pH or acidity. On average, a soft drink contains 0.001 M hydrogen ions (H + ). Report the charge on the hydrogen ions. Source: Millipore Sigma Identify if the hydrogen ions are cations or anions. Calculate the mass of hydrogen ions contained in a one- liter soft drink. 21 Blank Slide for Notes Knowledge Development Questions Honey Doping Salt Identification You are working for a government agency An unlabeled salt has cations with atomic masses inspecting the quality of honey produced across of 39 amu (𝐴 = 93.3 %) and 41 amu (𝐴 = 6.7 %). the industry. A sample from one company contains The cations are isotopes of the same element. The 1.678 mg of 13 C and 139.2 mg of 12 C. Pure honey anion is Cl−. The charge of the cations is 1+. 13C has a molar ratio of 12C = 0.01096. Doped honey will have a molar ratio larger than this. 1. Report the number of electrons in an atom of the anion. 1. Calculate the molar ratio of 13 C to 12 C in the 2. Calculate the average atomic mass of the company’s sample. cations. 2. Compare the ratio of carbon isotopes in the 3. Identify the element of the cations. company’s sample with the standard ratio. 4. Report the number of electrons in each cation. 3. Report if the company has been doping their honey with other sugars. 23 References Periodic Table – Larger Version. (2021) Math and Science. Retrieved May 20, 2023, from https://www.mathtutordvd.com/public/Periodic-Table-Larger-Version.cfm Hunajakennoja. (2013, April) Hunaja Ytyhma. Retrieved May 20, 2023, from https://hunaja.fi/en/about-honey/ Chemistry: Human Activity, Chemical Reactivity; 2nd ed., Nelson Education Ltd.: Toronto, 2015. Ch. 2.2, 2.4, 2.7, ,2.8, 2.9, 2.10, 2.11, 2.12, 2.13, 3.2, 3.5, 6.2, 6.4, 11.1, 11.2, 12.7, 22.3, 24.2, 24.3 Resources 24 Isotopic Abundance and Average Atomic Mass Silver has two stable isotopes: one containing 60 neutrons (51.4% relative abundance) and one containing 62 neutrons (48.6% relative abundance). Calculate the average atomic mass of silver from the isotopic abundances. Discuss any discrepancies with the average atomic mass reported in the periodic table. Source: https://www.mathtutordvd.com/public/Periodic-Table-Larger- Version.cfm 26