Chemical Bonding Theories Valence Electrons Classification Valence electrons are categorized based on orbital occupancy (0 = empty, 1 = half-filled, 2 = full). Atoms with a single valence electron can share it, forming a bonding electron. Atoms with full valence orbitals repel nearby orbitals, creating lone pairs. Covalent Bonding In covalent bonds, both atoms have high electronegativity, leading to shared electrons. Diatomic Cl2 exhibits a nonpolar covalent bond. Polar covalent bonds result from different electronegativities between atoms. Ionic Bonding Atoms with significantly different electronegativities form ionic bonds through electron transfer. This transfer creates positive and negative ions that attract each other. Metallic Bonding Atoms with low electronegativity share valence electrons without a chemical reaction. Electrons move freely between atoms due to vacant valence orbitals, resembling a glue of negative electrons holding positive nuclei. Molecular Elements and Lewis Formulas Molecular Elements Several molecular elements are diatomic or polyatomic. Examples include hydrogen (H2), nitrogen (N2), and oxygen (O2). Determining Lewis Formulas Understanding bonding capacity helps predict molecular compound structures. Atoms like carbon, nitrogen, oxygen, halogens, and hydrogen have specific bonding capacities. Lewis Formulas Determination Steps involve counting valence electrons, arranging atoms, placing lone pairs, and ensuring octet completion. For polyatomic ions, square brackets indicate the Lewis formula with the net charge outside. Polarity and Intermolecular Forces Polarity in Molecules Polar molecules exhibit asymmetric electron distribution, leading to partial positive and negative charges. Nonpolar molecules have symmetrical electron distribution. Polarity can be demonstrated by observing interactions with charged objects. Explaining Polarity Polarity in covalent bonds relates to electronegativity differences between bonded atoms. Greater electronegativity difference results in more polar bonds. Hydrogen bonding occurs with strongly electronegative atoms like N, O, and F. Intermolecular Forces Three types of intermolecular bonds exist: dipole-dipole, London dispersion, and hydrogen bonding. Dipole-dipole forces attract polar molecules, influencing properties like solubility. London forces involve temporary dipoles, while hydrogen bonding is specific to hydrogen atoms bonded to electronegative atoms. Comparing Kelvin and Celsius Scales Temperature Conversion To convert Celsius to Kelvin, add 273 (K = °C + 273). Conversely, to convert Kelvin to Celsius, subtract 273 (°C = K - 273). For example, 254 K is -19°C, and -34°C is 239 K. Temperature and Pressure Atmospheric Pressure Pressure exerted by air on all objects Measured in kilopascals (kPa) Impacts weather patterns and altitude effects Varies with elevation and weather conditions Gas Laws Boyle's Law: Inverse relationship between pressure and volume Charles' Law: Direct relationship between volume and temperature Combined Gas Law: Combines Boyle's and Charles' Laws Applications in scuba diving and weather balloons Molar Mass and Volume Molar Mass Calculations Determining molar mass of compounds like methanol Sum of atomic masses in a molecule Used in stoichiometry and chemical reactions Critical for quantitative analysis in chemistry Molar Volume Concepts Molar volume at STP and SATP Conversion factor for gas volume calculations Relates volume to moles of gas Practical applications in gas storage and transport Ideal Gas Law and Solutions Ideal vs. Real Gases Ideal gas assumptions and behavior Real gas deviations at extreme conditions Impacts of temperature and pressure on gas properties Relevance in industrial and environmental contexts Ideal Gas Law Applications Calculating gas mass using pressure, volume, and temperature Predicting gas volume under different conditions Practical examples in gas storage and engineering Importance in chemical reactions and material synthesis Acids and Bases Empirical Definitions Acid - substance that dissolves in water and tastes sour, turns blue litmus red, conducts electricity, reacts with active metals to produce H2(g), and neutralizes bases. Base - substance that dissolves in water and tastes bitter, feels slippery, turns red litmus blue, conducts electricity, and neutralizes acids. Theoretical Definitions - Arrhenius Acid - forms an acidic solution by producing free hydrogen ions (H+(aq)) in solution. Base - forms a basic solution by producing free hydroxide ions (OH-(aq)) in solution. Theoretical Definitions - Modified Definition Acid - species that forms an acidic solution by reacting with water to produce hydronium ions (H3O+(aq)). Base - species that forms a basic solution by reacting with water to produce hydroxide ions (OH-(aq)). Hydronium Ion and pH Scale Hydronium Ion Discovery Hydronium ion (hydrated proton) discovered by Paul Giguère at Université Laval in 1957. pH Scale and Formulas pH = -log[H3O+(aq)], pOH = -log[OH-(aq)] pH scale communicates hydronium ion concentrations between 0 and 14. Number of digits in pH or pOH equals significant digits in corresponding ion concentration. Inverse relationship exists between ion concentration and pH or pOH. Acid-Base Indicators Common Indicators Bromothymol blue: yellow (pH 6.0-7.6) to blue Phenolphthalein: colorless (pH 8.2-10.0) to pink Strong and Weak Acids/Bases Modified Arrhenius Theory Strong Acids: high conductivity, react completely with water to form many hydronium ions. Weak Acids: low conductivity, react incompletely with water to form relatively few hydronium ions. Strong Bases: dissociate completely to release hydroxide ions. Weak Bases: react partially with water to produce relatively few hydroxide ions. Chemical Reactions and Stoichiometry Ionic Equations BaCl2(aq) + Na2SO4(aq) -> BaSO4(s) + 2NaCl(aq) Ba2+(aq) + 2Cl-(aq) + 2Na+(aq) + SO4(aq) -> BaSO4(s) + 2Na+(aq) + 2Cl-(aq) Ba2+(aq) + 2Cl-(aq) + 2Na+(aq) + SO4(aq) -> BaSO4(s) + 2Na+(aq) + 2Cl-(aq) Ba2+(aq) + SO4(aq) -> BaSO4(s) Spectator Ions Ions present but not participating in a reaction are spectator ions. Analogous to spectators at a sports game, they are present but do not engage in the game. Limiting and Excess Reagents Identification Limiter reagent is fully consumed, halting the reaction. Presence of excess reagent leads to leftover amounts post-reaction. Calculation Excess reagent quantity is the surplus after the reaction. To ensure complete reaction, a 10% excess of reagent is often used. Stoichiometry Calculations Mass Stoichiometry Given a chemical equation, calculate the mass of a substance required or produced. Example: Determine the mass of iron(III) oxide needed to produce 100.0g of iron. Percent Yield Percent yield compares actual and theoretical yields. Factors affecting yield include equipment limitations, chemical purity, and qualitative judgments. Gas Stoichiometry Volume Calculations Calculate gas volumes using molar ratios and known quantities. Example: Determine the volume of oxygen needed for the combustion of 300g of propane. Molar Volume Molar volume is crucial in gas stoichiometry, akin to molar mass in gravimetric stoichiometry. Still working on this section. Refresh the page to see if it’s ready.