Chem 1120 1st Edition Lecture 19 Outline of Last Lecture I. Solubility EquilibriaII. 4 Factors Affecting Solubilitya. Common Ion Effectb. pHc. Presence of Complexing Agentsd. Amphoterism III. Precipitation and Separation of IonsOutline of Current Lecture I. Periodic Trends and Classes of ElementsII. Group 1A (1) HydrogenCurrent LectureI. Although we went over trends last semester, we are going to review them this chapter and go more in depth with them now:As you go across the periodic table:Increasing Ionization EnergyDecreasing Atomic RadiusIncreasing ElectronegativityDecreasing Metallic CharacterAs you go down the periodic table:Decreasing Ionization EnergyThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Increasing Atomic RadiusDecreasing ElectronegativityIncreasing Metallic CharacterClasses of Elements:Metals = majority of periodic table, good conductors of heat and elec-tricity, mostly positive oxidation numbers, and except for Hg, solids in their standard stateMetalloids = properties of both metals and nonmetals, many are semi-conductors (B,Si,Ge,As)Nonmetals = poor conductors of heat and electricity, both positive and negative oxidation numbers common, noble elements are gases at standard state, Br2 is a liquidNon-metallic elements = only 17 out of 114, life is based on them, (C, O, H, N, P, S), negative oxidation states when combined with metals, can have positive oxidation states in bonding to other non-metals, higher elec-tronegativities than the metals, nonmetal oxides are acidic, combine with water to give oxy-acidsIonization Energy = minimum energy needed to remove an electron from a gaseous atom A or ion; endothermic (trend above)Electron Affinity = negative of enthalpy for electron gain by atom A; smaller than ionization energy, exothermic except for noble gases and alka-line earth elementsElectronegativity = tendency of an atom in a molecule to gain addi-tional electron density while retaining its original electron densityWithin a group, smaller atoms are more likely to form pi bonds becausethey can get closer to other atoms (overlap more) II. Group 1A (1) HydrogenHydrogen is very common but unique at the sea time. It makes up: 75% of the mass of the universe, 11% of the mass of the oceans, 0.15% of the Earth’s crust, 0.4% of the mass of the atmosphere, 9.5% of the mass of a hu-man bodyHydrogen has three isotopes——>Hydrogen should not really belong to any group, it is unique in its electron configuration and is the only element with an un-filled 1s va- lence shell that can either gain or lose an elec- tronIonic hydrides are good reducing agents; there are 3 hydride types:Ionic hydridesMetallic hy- dridesCovalent hy- drides(organic com- pounds are covalent hydrides)Molecular hydrides: formed between hydrogen and nonmetals or metalloids, usually gases or liquids at room temperature and normal atmospheric pres-sure, stability of the nonmetal hydrides decreases down the groupProperties of Hydrogen: very large bond enthalpies (reacts slowly at room temperature), forms strong bonds with other elements (its reactions are gen-erally quite exothermic), forms H-bonds with electronegative O, F, and N (strong intermolecular forces, H-bonds are fundamental to life i.e proteins, DNA)Hydrogen Fuel Cells•using hydrogen as a fuel would have many advantages: its reaction with water is highly exothermic, water is the only product•problem: how will we make the H2?Hydrogen production •hydrogen is commercially produced from reaction of methane with steam at 1100 degrees C or carbon and steam above 1100 degrees C•its production from the electrolysis of water is not efficient energyHydrogenation = addition of dihydrogen to multiple bonds (usually Carbon double bonds and triple