Law of Conservation of Mass. Law of Constant Composition. Modern Atomic Theory. Structure of the Atom? Structure of the Atom. Structure of the Atom

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1 Law of Conservation of Mass rancie came away from her first chemistry lecture in a glow. n one hour she found out that everything was made up of atoms which were in continual motion. She grasped the idea that nothing was ever lost or destroyed. Even if something was burned up or rot away, it did not disappear from the face of the earth; it changed into something else - gases, liquids, and powders. Everything, decided rancie after that first lecture, was vibrant with life and there was no death in chemistry. She was puzzled as to why learned people didn't adopt chemistry as a religion. A Tree Grows in Brooklyn Betty Smith, 19 Law of Constant Composition... The properties of true compounds are invariable as is the ratio of their constituents. The native oxides follow the same relations of composition as the artificial. We find in the bosom of the earth copper oxide containing 20 per cent of oxygen, arsenic with, lead with 9, antimony with 0, iron with 28 and 8, and others still. We must conclude that nature operates not otherwise in the depths of the world than at its surface or in the hands of man. J. L. Proust Modern Atomic Theory? John Dalton British elements made of small, indivisible particles: atoms 2. atoms of a given element all alike (properties), but differ from atoms of every other element in some way: mass?. compounds form when atoms of more than one element combine; a given compound always has same relative number and kind of atom: Law of Constant Composition. atoms are not changed into different atoms by chemical reactions; atoms are neither created nor destroyed: Law of Conservation of Matter So orton stopped splashing. e looked towards the sound. That s funny, thought orton. There s no one around. Then he heard it again! Just a very faint yelp As if some tiny person were calling for help. ll help you, said orton. But who are you? Where? e looked and he looked. e could see nothing there But a small speck of dust blowing past though the air. say! murmured orton. ve never heard tell f a small speck of dust that is able to yell. So you know what think? Why, think that there must Be someone on top of that small speck of dust! Some sort of a creature of very small size, too small to be seen by an elephant s eyes... And that Yopp That one small, extra Yopp put it over! inally, at last! rom that speck on that clover Their voices were heard! They rang out clear and clean. And the elephant smiled. Do you see what mean? They ve proved they ARE persons, no matter how small. electron, e ; fundamental particle cathode-ray tube electron, e ; fundamental particle Plum pudding atomic model e raisins attracted to positive: e negatively charged mass = 5.68 x 10 9 g/c (from deflection) charge charged pudding 1

2 Atomic umber Thomson on the size of the electron Robert Millikan American 1909 electron, e ; fundamental particle plum pudding atomic model oil drop experiment charge on e : x C oil drops atomizer "Could anything at first sight seem more impractical than a body which is so small that its mass is an insignificant fraction of the mass of an atom of hydrogen? --which itself is so small that a crowd of these atoms equal in number to the population of the whole world would be too small to have been detected by any means then known to science." X-rays microscope Robert Millikan American 1909 enri Becquerel electron, e ; fundamental particle plum pudding atomic model oil drop experiment charge on e : x C mass of e : x g Marie and Pierre Curie rench radioactivity a particles: e 2 b particles: e g radiation: X-rays Expected results: Rutherford s Experiment gold-foil experiment: a particle probes fluorescent detector (ZnS) Au foil Au atom Ernest Rutherford ew Zealand Pb box with a 2 source (RaCl 2 ) few atoms thick Rutherford s Experiment gold-foil experiment: a particle probes Ernest Rutherford ew Zealand most went directly through; but a few reflected back! planetary model gold-foil experiment: a particle probes atomic number (Z) (using X-rays) Ernest Rutherford ew Zealand enry Moseley 191 interpretation: t was about as credible as if you had fired a 15-inch shell at a piece of tissue paper and it came back and hit you. integers (on periodic table) are characteristic of the elements [and] the same as # of electrical units [ charges] in the nucleus. Emitted X-rays Wavelength 2

3 discovered the proton: Ernest Rutherford 2 a 2 p ew Zealand 186 x heavier than e ( x 10 2 g) discovered the neutron: Be a C n 0 slightly larger than p ( x 10 2 g) James Chadwick 192 particle charge relative mass p n e 5.6 x 10 A Z X Structure of eutral Atom e orbiting small, dense nucleus: p n element name A 6 atomic number Z = # p (Ger zahl number ) identity of atom # e = # p neutral atom mass number A = # p # n 0 atomgewicht related to PT mass lithium 6 Evidence of Atoms Atomic orce Microscope Metals, onmetals, Metalloids nonmetals e Be B C e a Mg metals Al Si P S Cl Ar K Ca Sc Ti V Cr Mn e Co i Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr b Mo Tc Ru Rh Pd Ag Cd n Sn Sb Te Xe Cs Ba Lu f Ta W Re s r Pt Au g Tl Pb Bi Po At Rn r Ra Lr Rf Db Sg Bh s Mt Ds Rg Cn l Lv metalloids or semi-metals La Ce Pr d Pm Sm Eu Gd Tb Dy o Er Tm Yb Ac Th Pa U p Pu Am Cm Bk Cf Es m Md o Periodic Table amilies Be B C e a Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn e Co i Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr b Mo Tc Ru Rh Pd Ag Cd n Sn Sb Te Xe Cs Ba Lu f Ta W Re s r Pt Au g Tl Pb Bi Po At Rn r Ra Lr Rf Db Sg Bh s Mt Ds Rg Cn l Lv La Ce Pr d Pm Sm Eu Gd Tb Dy o Er Tm Yb Ac Th Pa U p Pu Am Cm Bk Cf Es m Md o e g cinnabar Compounds S C S Svante Arrhenius Swedish carbon disulfide 188 alkali metals pnictogens e noble gases Be alkaline-earth metals chalcogens La lanthanides Sc transition metals halogens Ac actinides

4 onic (Gr: mobile) collections of oppositely charged particles: ions formed from atoms or groups of atoms by losing e or gaining e cation () anion () (e < p ) (e > p ) #, # 1, 1, X n n a Mg p 12 p 18 p 19 p 10 e 10 e 10 e 10 e (n = # e gained) (n = # e lost) very different from neutral atom Cl 17 p 18 e 1 a on Charges from Periodic Table 2 () 2 1 metal ion C Mg name as element Al P S Cl K Ca Rb Sr Cs Ba Ra nonmetal ion name ide suffix empirical formula: cation anion; / in a ratio that adds to 0: hydride, carbide, nitride, oxide, fluoride, phosphide, sulfide, chloride, selenide, bromide, iodide magnitude of charge given first, followed by or 1 and 1 given as and Se Br on-predictable Charges on Monatomic Cations all other metal ions have variable charges 1, 2,,, etc? Sc Ti V Cr Mn e Co i Cu Zn Ga Y Zr b Mo Tc Ru Rh Pd Ag Cd n Sn Lu f Ta W Re s r Pt Au g Tl Pb Bi Po Lr Rf Db Sg Bh s Mt Ds Rg Cn name includes charge in (Roman numerals): e 2 iron() e iron() e iron(v) Cu 2 Cu Sn 2 tin() Sn tin(v) g 2 mercury() Cu copper() copper() copper() l Lv 1. binary: 2 atom types: metal nonmetal a. metal ion name as element (predictable) or element (Roman numeral) charge (not) K Ca Sc Ti V Cr Mn e Co i Cu Zn Ga Rb Sr onic: Recognize, ormula and ame b. modify nonmetal ion element name: ide 1 carbide, nitride, oxide, fluoride, phosphide, sulfide, chloride, selenide, 2 C bromide, iodide, hydride a Mg Al P S Cl Y Zr b Mo Tc Ru Rh Pd Ag Cd n Sn Cs Ba Lu f Ta W Re s r Pt Au g Tl Pb Bi Ra Lr Rf Db Sg Bh s Mt Ds Rg Cn 2. >2 atom types: polyatomic ions; formula, name and charge l Se Br 2 Lv 1 Polyatomic Anions 1 2 ate, ite nitrate S 2 sulfate P phosphate 2 nitrite S 2 sulfite P phosphite S hydrogen sulfate Cl hypochlorite (hypo-, fewer) Polyatomic Cations Cl 2 chlorite (also Br, ) ammonium Cl chlorate g 2 2 mercury() Cl perchlorate (per-, most) mercurous no ite C 2 2 acetate C 2 carbonate C 2 2 oxalate M containing Mn permanganate Cr 2 chromate Cr dichromate (di-, 2) polyatomic ide azide 2 2 peroxide hydroxide C cyanide onic: aming, Recognizing, and ormula CuS Cu 2 S 2

5 onic: ormula and ame Ba a aluminum sulfide Cu Sn 2 P ecl 2 iron() chloride Cu 2 S 2 i 2 Cr 2 Ga 2 (C ) magnesium nitrate P Molecular binary: 2 atom types recognize: all nonmetals 2 atoms, uncharged, act as a unit: B C Si 2 2 P S Cl 2 formula cannot be predicted from the elements some elements are molecular 2 2 Cl 2 Se Br Br 2 2 Molecular: ormula and aming Molecular: Recognizing, ormula, and aming formula: most metallic then most nonmetallic name: empirical: molecular: structural: smallest ratio exact number shows connectivity B hydrogen peroxide 2 2 first atom named as a cation (it s not); second as an anion (it s not); # of each atom with prefix C Si P S Cl Se Br Cl P 2 5 C S 2 Br boron trihydride tetraphosphorus trisulfide mono 1 di 2 tri tetra penta 5 hexa 6 hepta 7 octa 8 nona 9 deca 10 undeca 11 dodeca dinitrogen tetroxide 2 5 ther aming hydrates ionic with specific # attached 2 dot formula # 2 CuS 5 2 name prefixhydrate copper() sulfate pentahydrate anion ide ate ite acids recognize: contains, given first name: from anion acid hydroic C cyanide C hydrocyanic acid ic S 2 sulfate 2 S sulfuric acid ous Cl 2 chlorite Cl 2 chlorous acid 5