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Early Atomic TheoryAtomsPowerPoint PresentationSlide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Atomic Number, ZMass Number, ASlide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30MoleculesCompositionTypes of FormulasSlide 34IonsFormation of Monatomic IonsSlide 37Slide 38Polyatomic IonsSlide 40Slide 41Writing Ionic Compound FormulasIonicSlide 44Slide 45Binary Molecular CompoundsAcidsSlide 48Early Atomic TheoryAtoms, Molecules, and IonsPreparation for College ChemistryLuis AvilaColumbia UniversityDepartment of ChemistryAtomsIsotopesAtomic theoryComponents of the AtomAtomic NumberMass Number•Nature consists solely of an infinite number of indivisible particles, having shape, size, impenetrability, and no further properties. These particles move through an otherwise empty space. 440 BCLEUCIPUS of Miletus and his disciple DEMOCRITUS of Abdera:470 BCPLATO and ARISTOTLE reinforces: •Matter is composed of four elements: EARTH, AIR, WATER, FIRE 384 - 270 BCEMPEDOCLES: •Matter is composed of four elements: EARTH, AIR, WATER, FIRE •The shape, size, location, and movement of these particles make up literally all of the qualities, relations, and other features of the natural world. Atomic Theory. Early Thoughts1500’sFRANCIS BACON:1500’sROBERT BOYLE and ISAAC NEWTON:•Used atomic concepts to interpret physical phenomena. 17th CenturyGALILEO GALILEI: •Appearance of a new substance through chemical change involves rearrangement of parts too small to be seen. •Heat might be a form of motion of small particles.Dalton’s Model of the Atom1. Elements consist of tiny particles called atoms.2. Atoms of the same element are alike in mass and size.3. Atoms of different elements differ in mass and size.4. Chemical compounds form by the union of two or more atoms of different elements.5. Atoms combine to form compounds in simple numerical ratios, such as 1:2, 2:3, etc.6. Atoms of two elements may combine in different ratios to form more than one compound.1803 - 1810Consequences of Dalton’s LawThe Law of conservation of Mass:The Law of Constant Composition:The Law of Multiple Proportions:“There is no detectable change in mass in an ordinary chemical rxn.”“A compound always contains the same elements in the same proportions by mass.”“The masses of one element that combine with a fixed mass of the second element are in a ratio of small whole numbers.”Composition of CompoundsPercent HPercent OAtomic CompositionWaterHydrogen Peroxide11.288.85.994.12H + 1O2H + 2 OA compound always contains two or more elements combinedin a definite proportion by mass.Atoms of two or more elements may combine in different ratiosto produce more than one compound.Careful experimentation lead Proust to demonstrate H2 + Cl22HClH2SO4 + 2NaCl2HCl + Na2SO4Proportions by mass of elementsin a compound VARY OVER A CERTAIN RANGEProportions by mass of elements in a compound ARE FIXED. VARIATIONS ARE DUE TO IMPURITIES.Claude Berthollet:Joseph Proust:THE LAW OF DEFINITE PROPORTIONS (CONSTANT COMPOSITION):“The proportions by mass of the elements in a compound ARE FIXED, and do not depend on its mode of preparation.”Wüstite, an iron oxide whose simplest formula is FeO, with 77.73%Fe.All gaseous compounds OBEY THE LAW OF DEFINITE PROPORTIONS.Certain SOLIDS are exceptions of the Law of Constant Composition: NON STOICHIOMETRIC COMPOUNDS (BERTHOLLIDES)Its composition truly ranges from Fe0.95O (76.8% Fe) to Fe0.85O (74.8% Fe) depending of the method of preparation.The composition of a compound is shown by its CHEMICAL FORMULA.C + O2AC + O2BCHEMICAL ANALYSIS:If A is CO then B = CO2 For a FIXED mass of C the ratio of O in A and B is: If A is CO2 then B is C2O4Let’s take the elements C and O:(1.000 g C and 1.333 g O)(1.000 g C and 2.667 g O)1.333 : 2.667 or 1: 2We are unable to say which one is the right formula, but we know the ratio C : O is the QUOTIENT OF INTEGERS.As + SAAs + SB0.4820.642=2 : 3If A is As2S2 then B = As2S3CHEMICAL ANALYSIS:For Arsenic and Sulfur:(1.000 g As and 0.482 g S)(1.000 g As and 0.642 g S)For a FIXED mass of As the ratio of S in A and B is:Certain substances when dissolved in water can conduct an electric current.ANIONS: NEGATIVE IONS that “travel to the ANODE (positive electrode).There must be some FUNDAMENTAL unit of electricity associatedwith atoms: ELECTRON.MICHAEL FARADAY:SVANTE ARRHENIUS:Water is not necessary IONIC SUBSTANCES conduct electricity when melted.CATIONS: POSITIVE IONS, they “travel” to the CATHODE (negative electrode)G. J. STONEY:189118871830’sCathode rays are ELECTRONS (e-) particles with a negative charge.1897The first sub-atomic particleJ.J Thomson Discovered the Electron1913ERNEST RUTHERFORD and HANS GEIGER with the apparatus for counting alpha particlesManchester, 1912 "It was as though you had fired a fifteen-inch shell at a piece of tissue paper and it had bounced back and hit you." The Nuclear AtomThe Nuclear AtomnpElectron regionNucleusArrangement of Subatomic ParticlesParticle Location Relative Charge Relative Mass (amu)proton Nucleus +1 1.00728neutron Nucleus 0 1.00867electron Outside nucleus-1 0.00055Properties of Subatomic ParticlesAtomic Number, Z Equals number of protons in nucleus Equals number of electrons in neutral atom Characteristic of a particular element Location of the element in the Periodic ChartMass Number, AA = number of protons + number of neutronsAtoms of the same element can differ in mass numberIsotope # Protons # Neutrons Z A SymbolCarbon-12 6 6 6 12Carbon-14 6 8 6 14€ 612C€ 614C11H12H13HZAENuclei RepresentationA - Z = number of neutronsFor light (Z < 20) isotopes the stable ratio is 1.0; with heavier isotopes it increases to 1.5. There are no stable isotopes for elements of Z > 83 (Bi).Too heavyemissionPrecise determination of the masses of individual atomsMeaning of Atomic Masses• Give relative masses of atoms based on C–12 scale. • The Most common isotope of carbon is assigned an atomic mass of 12 amu.• The amu is defined as 1/12 of the mass of one neutral carbon atom 1amu =1dalton=11212g612Cmol612C×1mol612C6.0221×1023atoms612C⎛ ⎝ ⎜ ⎞ ⎠ ⎟ =1.66054×10−24g/ atom612CA nickel atom is 58.69 / 40.08 = 1.464 times as heavy as a calcium ionIt is 58.69 / 10.81 = 5.29 times as heavy as a boron


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Columbia CHEM UN0001 - Early Atomic Theory

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