CHEM 1120 Edition 1nd Lecture 19 Outline of Last Lecture I Classes of elements a Metals b Metalloids c Nonmetals II Properties of Nonmetals III Review of Periodic properties a Ionization Energy b Electron Affinity c Electronegativity d Atomic Radii e Periodic Trends IV Group 1A Hydrogen a 3 isotopes b 3 types of hydrogen chemistry c Properties of hydrogen d Hydrogen production V Noble Gases Group 8A a Least reactive group Outline of Current Lecture I Halogens a Reactive Non metals b Properties c Preparation d Important compounds e Uses II Group 6A Oxygen Family a Allotropes of Oxygen b Oxides c Superoxides d Sulfur Current Lecture I Halogens 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 a b c d II Halogens have out electron configurations ns2np5 They have large electron affinities and ionization energies They tend to accept on electron to form anions Reactive Non metals i Monoanions are halides X ii A 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 iii F smal l reactive high electronegativity strong oxidizing agent iv Cl abundant biologically important strong oxidizing element v I least reactive and toxic of halogens weaker oxidizing agent biological trace element vi At radioactive e Properties i Very reactive good oxidizers react with nearly all metals and non metals can oxidize anions of halides below them on the periodic chart ii Properties of fluorine are unique reacts explosively with most elements oxidizes water iii Bigger the element bigger the bond length bump in bond energy near Cl decreases f Preparation of Halogens i Prepared from halides ii Electronegative F2 Cl2 must be prepared by electrolysis iii Fluorine cannot be prepared by aqueous electrolysis water is more easily oxidized F2 is prepared by the electrolysis of HF iv Chlorine prepared by electrolysis to give Cl2 and Na or Cl2 H2 and NaOH v Bromine and iodine prepared from seawater by oxidation with Cl2 g All halogens have a 1 oxidation state h Important compounds i Metal halides CaCl2 ii Oxides oxoacids and salts ClO2 HBrO3 KIO3 iii Hydrogen halides HCl iv Interhalogen compounds BrF5 v HX are acidic acid strength increases down the series vi HF is very reactive other HX less so i Uses for halogens i Chlorine most important industrially ii Bromine photographic film not an essential element for life iii Cl Br used to make non flammable clothing iv Iodine antiseptic Group 6A Oxygen Family a Group members exhibit covalent and ionic behaviors b Oxygen and Sulfur are nonmetals i Both form many covalent compounds c d e f g h i j ii Oxygen forms many ionic compounds sulfur forms fewer ionic compounds Se and Te are metalloids Po radioactive metal Allotropes of oxygen O2 and O3 i O2 used for respiration oxidant in acids prepared by fractional distillation of liquefied air ii Ozone O3 less stable than O2 toxic bent diamagnetic molecule used to purify water generated by lightning decomposes to O2 and O upon absorbing UV photons Sulfur i More than 10 allotropes most stable consisting of S8 rights Selenium i Se8 rings Oxides i Oxygen is the second most electronegative element ii Always has a negative oxidation state except when bound to F iii Acidic oxides like SO2 and SO3 form acids when exposed to water iv Basic oxides like BaO form a hydroxide ion when they react with water v Covalency 1 Alkali metal alkaline earth oxides are ionic 2 Oxides of the metals and metalloids are ionic in low oxidation states and polar covalent in high oxidation states 3 Oxides of the non metals are polar covalent vi Basicity 1 Decreases from left to right increases down rows vii Melting point 1 Metallic oxides have high melting points 2 Oxides of non metals are liquids or gases at ambient T viii Hydrogen Peroxide HOOH 1 Polar reactive molecule that disproportionates to H2O and O2 in presence of heat light some metals 2 Antiseptic oxidizes organic matter Superoxides i Most active metals form superoxides through reaction with O2 ii React with H2O to form O2 iii Peroxide and superoxide are metabolic byproducts that can do indiscriminate biological damage iv Enzymes catalase superoxide dismutase and peroxidase convert O2 into H2O and O2 Sulfur i Brittle soft yellow solid with low mp that facilitates its melting in rock with hot steam and transport to surface as emulsion ii Large oxidation number range 2 to 6 iii Use in gunpowder iv Organic compounds of sulfur 1 Compounds with SH groups are called thiols 2 Smell bad v Inorganic sulfides 1 Found in some protein active sites 2 Pyrites contain the disulfide ion 3 Minerals like galena and cinnabar vi Compounds of sulfur 1 Disulfides are important structural feature in proteins staple proteins together vii Sulfuric Acid 1 Versatile diprotic acid 2 Strong oxidizing agent and strong acid 3 1 chemical from dissolution 4 Concentrated 98