Periodic_props_s2008

Periodic_props_s2008 - Exam 3 Zn(OH 2-x Zn 2 2OH-1 x 2x 3.7...

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Unformatted text preview: Exam - 3 Zn(OH ) 2 -x Zn 2+ + 2OH -1 x 2x 3.7 10-4 g 1mol mol = 3.72 10-6 L 99.4 g L So lub ility = 3.7 10-4 g / L OH -1 = 2 3.72 10-6 pH = 8.87 Exam - 3 CHE 132 Exam 3 Distribution, Spring 2008 120 Number of Students 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 90 100 Percent Grade Main Group Elements Origin of the elements The universe was created about 15 billion years ago in a single violent event known as the Big Bang. All the space, time, energy, and matter that constitute today's universe originated in the Big Bang. The early universe was extremely small, dense, and hot. For the first fraction of a second, only energy existed. Expansion and Subsequent formation Light nuclides 1H, 2H, 3H, 4He Origin of the elements The young universe did not have a perfectly even distribution of energy and particles. These irregularities allowed forces to start to collect and concentrate matter. Concentrations of matter formed into clouds, then condensed into stars and the collections of stars we call galaxies. (Diameter = 300 light years 1ly = 10 trillion Km) Origin of the elements Concentrations of matter formed into clouds, then condensed into stars and the collections of stars we call galaxies. Nuclear Reactions !! Origin of the elements Nuclear Burning in Stars Elements from hydrogen to iron are formed inside stars via a sequence of nuclear fusion reactions B ns lio il o s 1 0 ear 4 1 H 2 He + 2 -1 e + 2 4 fy Star contracts and the core becomes hot and dense Helium burning 4 4 8 2 He + 2 He 4 Be 4 2 He + 48 Be 12C 6 Origin of the elements Nuclear Burning in Stars r Fu 12 6 4 2 4 2 rC he t on io act tr n Helium burning 4 4 8 2 He + 2 He 4 Be 4 2 4 8 C + 2 He 16O He + 48 Be 12C 6 20 He + 16O 10 Ne 8 20 24 He + 10 C 12 Mg 12 6 1 C + 12C 11 Na + 1 H 23 6 Burning continues up to iron-56 12 6 C + 16O 14 Si 28 8 Origin of the elements Origin of the elements Iron has the highest binding energy. In order to produce even heavier elements up to uranium, energy required. Origin of the elements Formation of Heavy Elements ! We are all remnants of Supernovae Explosions Development of the Periodic Table There were 114 elements known by 1999. The majority of the elements were discovered between 1735 and 1843. How do we organize 114 different elements in a meaningful way? Modern periodic table: arrange elements in order of increasing atomic number. Development of the Periodic Table Metals, Nonmetals, and Metalloids Metals, Nonmetals, and Metalloids Metals Metallic character refers to the properties of metals (shiny or lustrous, malleable and ductile, oxides form basic ionic solids, and tend to form cations in aqueous solution). Metallic character increases down a group. Metallic character decreases across a period. Metals have low ionization energies. Most neutral metals are oxidized rather than reduced. Metals, Nonmetals, and Metalloids Metals When metals are oxidized they tend to form characteristics cations. All group 1A metals form M+ ions. All group 2A metals form M2+ ions. Most transition metals have variable charges. Metals, Nonmetals, and Metalloids Metals Metals, Nonmetals, and Metalloids Metals Most metal oxides are basic: Metal oxide + water metal hydroxide Na2O(s) + H2O(l) 2NaOH(aq) Nonmetals Nonmetals are more diverse in their behavior than metals. When nonmetals react with metals, nonmetals tend to gain electrons: metal + nonmetal salt 2Al(s) + 3Br2(l) 2AlBr3(s) Metals, Nonmetals, and Metalloids Nonmetals \ Most nonmetal oxides are acidic: nonmetal oxide + water acid P4O10(s) + H2O(l) 4H3PO4(aq) Metalloids Metalloids have properties that are intermediate between metals and nonmetals. Group Trends for the Active Metals Group 1A: The Alkali Metals Alkali metals are all soft. Chemistry dominated by the loss of their single s electron: M M+ + eReactivity increases as we move down the group. Alkali metals react with water to form MOH and hydrogen gas: 2M(s) + 2H2O(l) 2MOH(aq) + H2(g) Group Trends for the Active Metals Group 1A: The Alkali Metals Alkali metal produce different oxides when reacting with O2: (oxide) 4Li(s) + O2(g) 2Li2O(s) 2Na(s) + O2(g) Na2O2(s) (peroxide) K(s) + O2(g) KO2(s) (superoxide) Alkali metals emit characteristic colors when placed in a high temperature flame. The s electron is excited by the flame and emits energy when it returns to the ground state. Group Trends for the Active Metals Group 1A: The Alkali Metals Li line: 2p 2s transition Na line (589 nm): 3p 3s transition K line: 4p 4s transition Group Trends for the Active Metals Group 2A: The Alkaline Earth Metals Alkaline earth metals are harder and more dense than the alkali metals. The chemistry is dominated by the loss of two s electrons: M M2+ + 2e-. Mg(s) + Cl2(g) MgCl2(s) 2Mg(s) + O2(g) 2MgO(s) Be does not react with water. Mg will only react with steam. Ca onwards: Ca(s) + 2H2O(l) Ca(OH)2(aq) + H2(g) Group Trends for Selected Nonmetals Hydrogen Hydrogen is a unique element. Most often occurs as a colorless diatomic gas, H2. It can either gain another electron to form the hydride ion, H-, or lose its electron to become H+: 2Na(s) + H2(g) 2NaH(s) 2H2(g) + O2(g) 2H2O(g) H+ is a proton. The aqueous chemistry of hydrogen is dominated by H+(aq). Group Trends for Selected Nonmetals Group 6A: The Oxygen Group As we move down the group the metallic character increases (O2 is a gas, Te is a metalloid, Po is a metal). There are two important forms of oxygen: O2 and ozone, O3. Ozone can be prepared from oxygen: 3O2(g) 2O3(g) H = +284.6 kJ. Ozone is pungent and toxic. Group Trends for Selected Nonmetals Group 6A: The Oxygen Group Oxygen (or dioxygen, O2) is a potent oxidizing agent since the O2- ion has a noble gas configuration. There are two oxidation states for oxygen: 2- (e.g. H2O) and 1- (e.g. H2O2). Sulfur is another important member of this group. Most common form of sulfur is yellow S8. Sulfur tends to form S2- in compounds (sulfides). Group Trends for Selected Nonmetals Group 7A: The Halogens The chemistry of the halogens is dominated by gaining an electron to form an anion: X2 + 2e- 2X-. Fluorine is one of the most reactive substances known: 2F2(g) + 2H2O(l) 4HF(aq) + O2(g) H = -758.7 kJ. All halogens consists of diatomic molecules, X2. Group Trends for Selected Nonmetals Group 7A: The Halogens Chlorine is the most industrially useful halogen. It is produced by the electrolysis of brine (NaCl): 2NaCl(aq) + 2H2O(l) 2NaOH(aq) + H2(g) + Cl2(g). The reaction between chorine and water produces hypochlorous acid (HOCl) which disinfects pool water: Cl2(g) + H2O(l) HCl(aq) + HOCl(aq). Hydrogen compounds of the halogens are all strong acids with the exception of HF. Group Trends for Selected Nonmetals Group 8A: The Noble Gases These are all nonmetals and monatomic. They are notoriously unreactive because they have completely filled s and p sub-shells. In 1962 the first compound of the noble gases was prepared: XeF2, XeF4, and XeF6. To date the only other noble gas compound known is KrF2. ...
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