Chemical Bonding the Classical Descrip4on Its easy Monday Oct 10 Wednesday Oct 12 Friday Oct 14 QUIZ 1 week of MONDAY OCT 10TH at secHons 20 mins Chapter 3 Chemical Bonding The Classical DescripHon 63 3 1 RepresentaHons of Molecules 65 3 2 The Periodic Table 70 3 3 Forces and PotenHal Energy in Atoms 73 3 4 IonizaHon Energies the Shell Model of the Atom and Shielding 79 3 5 Electron A nity 85 3 6 ElectronegaHvity The Tendency of Atoms to A ract Electrons in Molecules 88 Monday Oct 17 MID TERM 1 Represen4ng Molecules Empirical formula CH2O Molecular formula provides informa4on on atoms in one molecule C6H12O6 Glucose C2H4O2 ace4c acid CH2O formaldehyde Molecular formula C2H5O Condensed Structural formula CH3CH2OH line structures Ball and s4ck models Lewis dot diagrams line angle representa4ons space llingmodels Electrosta4c poten4al energy diagrams elpots Fig 3 1 p 66 Space lling models electrosta4c poten4al blue for nega4ve red for posi4ve So electron rich regions of the molecule appear blue while electron poor regions are red I put this here because this uneven distribu4on of charge is one of the reasons water molecules aRract each other CHIRALITY The two forms are also referred to by older names with dextro d referring to S carvone and laevo l referring to R carvone F Carvone forms two mirror image forms or enan4omers L R carvone smells like spearmint Its mirror image D S carvone smells like caraway The fact that the two enan4omers are perceived as smelling di erently is proof that olfactory receptors must contain chiral groups allowing them to respond more strongly to one enan4omer than to the other Not all enan4omers have dis4nguishable odors Fig 3 2 p 67 Chirality Greek word for hand cheir Crystal forms NaCl Cristabalite SiO2 Fig 3 3 p 70 The chemical proper4es of the elements are periodic func4ons of the atomic number Z places elements in groups arranged ver4cally and periods arranged horizontally There are eight groups of representa4ve elements or main group elements 10 groups and three periods of transi4on metal elements a period of elements with atomic numbers 57 through 71 called the rare earth or lanthanide elements a period of elements from atomic numbers 89 through 103 called the acHnide elements all of which are unstable and most of which must be produced ar4 cially the elements in the carbon group C Si Ge Sn Pb are designated as Group IV and the elements chromium Cr molybdenum Mo and tungsten W as the chromium group 1 Development of the periodic table Lothar Meyer and Dmitri Mendeleev independently and simultaneously organized the elements into tables based on their atomic weights 1871 Mendeleev predicted elements eka dvi and tri from the Sanskrit words for one two and three posi4ons below known elements Ekaboron and scandium Scandium oxide was isolated in late 1879 by Lars Fredrick Nilson Per Teodor Cleve recognized the correspondence and no4 ed Mendeleev late in that year Mendeleev had predicted an atomic mass of 44 for ekaboron in 1871 while scandium has an atomic mass of 44 955910 Ekaaluminium and gallium In 1871 Mendeleev predicted the existence of a yet undiscovered element he named eka aluminium because of its proximity to aluminium in the periodic table The table below compares the quali4es of the element predicted by Mendeleev with actual characteris4cs of Gallium discovered in 1875 Ekamanganese and techneHum Techne4um was isolated by Carlo Perrier and Emilio Segr in 1937 well ajer Mendeleev s life4me from samples of molybdenum that had been bombarded with deuterium nuclei in a cyclotron by Ernest Lawrence Mendeleev had predicted an atomic mass of 100 for ekamanganese in 1871 and the most stable isotope of techne4um is 98Tc 4 Ekasilicon and germanium Germanium was isolated in 1886 and provided the best con rma4on of the theory up to that 4me due to its contras4ng more clearly with its neighboring elements than the two previously con rmed predic4ons of Mendeleev do with theirs hRp www ptable com Fig 3 4 p 71 metals Non metals Metalloids semimetals par4ally conduct electricity Metals Nonmetals Metalloids Metals and nonmetals are dis4nguished by the presence or absence of a characteris4c metallic luster good or poor ability to conduct electricity and heat and malleability or briRleness Certain elements boron silicon germanium arsenic an4mony and tellurium resemble metals in some respects and nonmetals in others and are therefore called metalloids or some4mes semimetals Their ability to conduct electricity for example is much worse than metals but is not essen4ally zero like the nonmetals Group I alkali metals soj metals low MPt 1 1 compounds with Cl NaCl RbCl Alkali metals The alkali metals are mostly silver colored except for metallic cesium which can have a golden 4nt These elements are all soj metals of low density In chemical terms all of the alkali metals react aggressively with the halogens to form ionic salts They all react with water to form strongly alkaline hydroxides 2 M s 2 H2O l 2 MOH aq H2 g Group II Alkaline earth metals for The alkaline earth metals contain beryllium Be magnesium Mg calcium Ca stron4um Sr barium Ba and radium Ra The alkaline earth metals are silver colored soj metals which react readily with halogens to form ionic salts and with water though not as rapidly as the alkali metals to form strong alkaline basic hydroxides For example where lithium sodium and potassium react with water at room temperature magnesium reacts only with steam and calcium with hot water Mg 2 H2O Mg OH 2 H2 Group VI Chalcogens O S Se Te This group is also known as the oxygen family react to form a 1 1 compound with the alkali earths CaO BaS 2 1 compounds with alkali metals Li2O Na2S Halogens F Cl Br I Asta4ne diatomic Solid Iodine Asta4ne Liquid Bromine Gas Fluorine Chlorine Owing to their high reac4vity the halogens are found in the environment only in compounds or as ions The term halogen means salt former they form SALTS Halogens Halogens F Cl Br I Asta4ne diatomic Solid Iodine Asta4ne Liquid Bromine Gas Fluorine Chlorine Owing to their high reac4vity the halogens are found in the environment only in compounds or as ions The term halogen means salt former they form SALTS Form ionic salts with Halogens in 1 1 ra4o LiF NaCl Post transi4on elements Al Ga In Sn Thalium Lead Transi4on elements are both duc4le and malleable and conduct electricity and heat They can have mul4ple oxida4on states The noble metals are considered to be ruthenium rhodium