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UI CHEM 1120 - Noble Gases, Halogens, and the Oxygen Family
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Chem 1120 1st Edition Lecture 20 Outline of Last Lecture I Periodic Trends and Classes of Elements II Group 1A 1 Hydrogen Outline of Current Lecture I Noble Gases II Halogens III Oxygen Family Current Lecture I Noble gases including He Ne Ar Kr Xe and Rn are extremely stable and unreactive mainly because all 8 electron shells are filled and they have the highest ionization energies Liquid He a noble gas with boiling point 4 2K is sometimes used as a coolant Ne is used in electric signs and Ar is used in light bulbs and as an insulating gas between panes in thermal windows Noble gases were considered inert until 1962 with the discovery of a compound containing Xe Noble gas compounds include These are most important when teaching the VSEPR geometries He and Ne compounds are unknown and He is the second most abundant element in the universe II The halogens including F Cl Br I and At have outer electron configurations of ns2np5 They have large electron affinities and ionization energies and they tend to accept one electron to form anions These 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 The halogens are reactive nonmetals The monoanions are called halides X At standard state F2 and Cl2 are yellowish gases Br2 is a red brown liquid and I2 is a red purple solid with high vapor pressure F fluorine small reactive high electronegativity strong oxidizing agent Cl chlorine abundant biologically important element strong oxidizing agent Br bromine liquid in elemental form I iodine least reactive and toxic as X2 of halogens weaker oxidizing agent biological trace element At astatine radioactive Halogen properties very reactive good oxidizers because of their electronegativities react with nearly all metals and nonmetals can oxidize anions of halides below them on the periodic chart Properties of fluorine are unique fluorine reacts explosively with most elements and oxidizes water The F F bond is the weakest then comes I I then Br Br and then Cl Cl The FF bond is the shortest and the repulsion of fluorine s lone pairs weakens the F F bond All halogens have a 1 oxidation state All but fluorine also have positive oxidation states up to 7 when bonded to more electronegative atoms Hydrogen halides HX HX are acidic and acid strength increases down the series HF HCl HBr HI III Group members of the oxygen family exhibit covalent ionic behaviors Oxygen and Sulfur are nonmetals and both form many covalent compounds Oxygen forms many ionic compounds and sulfur forms fewer ionic compounds Selenium and tellurium are metalloids Polonium is a radioactive metal An allotrope is a different crystalline or molecular form of an element for example O2 and O3 are allotropes of oxygen Dioxygen O2 is a strong oxidant but O3 is stronger O2 is used by animals for respiration and is a plant waste product Ozone O3 is less stable than O2 and is a toxic astringent pale blue gas O3 is a bent diamagnetic molecule used to purify water to remove bacteria viruses and organic contaminants Oxides Oxygen is the second most electronegative element It always has a negative oxidation state except when bonded to F Acidic oxides like SO2 and SO3 form acids when exposed to water and basic oxides like BaO form a hydroxide ion when they react with water Oxides of the metals and metalloids are ionic in low oxidation states 1 2 3 and polar covalent in high oxidation states 4 5 6 7 Basicity decreases from left to right Na2O KO2 basic SO3 acidic Metallic oxides have high melting points solids and oxides of nonmetals are liquids or gases at standard temperature Hydrogen peroxide polar reactive molecule that disproportionates to water and oxygen in presence of heat light some metals and it is an antiseptic Enzymes catalase and peroxidase convert O22 and O2 to water and O2 reducing in vivo damage Superoxides have an oxidation state of 1 2 and react with water to form O2


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UI CHEM 1120 - Noble Gases, Halogens, and the Oxygen Family

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