apchapt2 - History Greeks Democritus and Leucippus - atomos...

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Unformatted text preview: History Greeks Democritus and Leucippus - atomos I Aristotle- elements AristotleI Alchemy I 1660 - Robert Boyle- experimental Boyledefinition of element. I Lavoisier- Father of modern chemistry LavoisierI He wrote the book- used measurement bookI I Chapter 2 Atoms, Molecules, and Ions Laws Conservation of Mass I Law of Definite Proportion- compounds Proportionhave a constant composition by mass. I They react in specific ratios by mass. I Multiple Proportions- When two elements Proportionsform more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers. I I What?! Water has 8 g of oxygen per g of hydrogen. I Hydrogen peroxide has 16 g of oxygen per g of hydrogen. I 16/8 = 2/1 I Small whole number ratios Example of Law Of Multiple Proportions Mercury has two oxides. One is 96.2 % mercury by mass, the other is 92.6 % mercury by mass. I Show that these compounds follow the law of multiple proportion. I Speculate on the formula of the two oxides. I Your Turn I Nitrogen and oxygen form two compounds. Show that they follow the law of multiple proportions Compound A Compound B Amount N 1.206 g 1.651g Amount O 2.755 g 4.714 g 1 Dalton's Atomic Theory 1. Elements are made up of atoms 2. Atoms of each element are identical. Atoms of different elements are different. I 3. Compounds are formed when atoms combine. Each compound has a specific number and kinds of atom. I 4. Chemical reactions are rearrangement of atoms. Atoms are not created or destroyed. I I I A Helpful Observation Gay-LussacGay-Lussac- under the same conditions of temperature and pressure, compounds always react in whole number ratios by volume. I Avagadro- interpreted that to mean AvagadroI at the same temperature and pressure, equal volumes of gas contain the same number of particles I (called Avagadro's hypothesis) Experiments to determine what an atom was I Thomson's Experiment Voltage source J. J. Thomson- used Cathode ray tubes Thomson- - + Thomson's Experiment Voltage source Thomson's Experiment Voltage source - + - + 2 Thomson's Experiment Voltage source Thomson's Experiment Voltage source I + I - + Passing an electric current makes a beam appear to move from the negative to the positive end Passing an electric current makes a beam appear to move from the negative to the positive end Thomson's Experiment Voltage source Thomson's Experiment Voltage source I + I - + Passing an electric current makes a beam appear to move from the negative to the positive end Passing an electric current makes a beam appear to move from the negative to the positive end Thomson's Experiment Voltage source Thomson's Experiment Voltage source + I By adding an electric field I By adding an electric field 3 Thomson's Experiment Voltage source + Thomson's Experiment Voltage source + I By adding an electric field I By adding an electric field Thomson's Experiment Voltage source + Thomson's Experiment Voltage source + I By adding an electric field I By adding an electric field Thomson's Experiment Voltage source + I I Thomsom's Model Found the electron Couldn't find positive (for a while) I Said the atom was like plum pudding I A bunch of positive stuff, with the electrons able to be removed I By adding an electric field he found that the moving pieces were negative 4 Millikan's Experiment Atomizer Millikan's Experiment Atomizer Oil droplets + Oil Microscope Microscope + Oil Millikan's Experiment Millikan's Experiment + X-rays X-rays give some drops a charge by knocking off electrons Millikan's Experiment Millikan's Experiment + + + + They put an electric charge on the plates Some drops would hover 5 Millikan's Experiment + Millikan's Experiment + + - - + + + + + + + Measure the drop and find volume from 4/3r3 Find mass from M = D x V Millikan's Experiment I Radioactivity Discovered by accident I Bequerel I Three types alpha- helium nucleus (+2 charge, large alphamass) beta- high speed electron beta gamma- high energy light gamma- + + From the mass of the drop and the charge on the plates, he calculated the charge on an electron Rutherford's Experiment Used uranium to produce alpha particles Aimed alpha particles at gold foil by drilling hole in lead block I Since the mass is evenly distributed in gold atoms alpha particles should go straight through. I Used gold foil because it could be made atoms thin I I Lead block Uranium Florescent Screen Gold Foil 6 What he expected Because Because, he thought the mass was evenly distributed in the atom What he got How he explained it Atom is mostly empty Small dense, positive piece at center I Alpha particles are deflected by it if they get close enough I I + + 7 Modern View The atom is mostly empty space I Two regions I Nucleus- protons and Nucleusneutrons I Electron cloud- region cloudwhere you have a chance of finding an electron I I SubSub-atomic Particles Z - atomic number = number of protons determines type of atom I A - mass number = number of protons + neutrons I Number of protons = number of electrons if neutral Symbols Chemical Bonds The forces that hold atoms together I Covalent bonding - sharing electrons I makes molecules I Chemical formula- the number and type of formulaatoms in a molecule I C2H6 - 2 carbon atoms, 6 hydrogen atoms, I I Z 23 X 11Na A Structural formula shows the connections, but not necessarily the shape. I Structural Formula There are also other model that attempt to show three dimensional shape I Ball and stick (see the models in room) I H H C H H C H H I Space Filling 8 Ions Atoms or groups of atoms with a charge CationsCations- positive ions - get by losing electrons(s) I Anions- negative ions - get by gaining Anionselectron(s) I Ionic bonding- held together by the opposite bondingcharges I Ionic solids are called salts I I I I Polyatomic Ions Groups of atoms that have a charge Yes, you have to memorize them. I List on page 65 Periodic Table I Metals Conductors I Lose electrons I Malleable and ductile Nonmetals Brittle Gain electrons I Covalent bonds I I SemiSemi-metals or Metalloids 9 Alkali Metals Alkaline Earth Metals Halogens Transition metals Noble Gases Inner Transition Metals 10 +1+2 -3 -2 -1 I I Naming compounds Two types Ionic - metal and non metal or polyatomics I Covalent- we will just learn the rules for 2 Covalentnonnon-metals Ionic compounds If the cation is monoatomic- Name the monoatomicmetal (cation) just write the name. I If the cation is polyatomic- name it polyatomicI If the anion is monoatomic- name it but monoatomicchange the ending to -ide I If the anion is poly atomic- just name it atomicI practice I I Covalent compounds Two words, with prefixes I Prefixes tell you how many. I mono, di, tri, tetra, penta, hexa, septa, nona, deca I First element whole name with the appropriate prefix, except mono I Second element, -ide ending with appropriate prefix I Practice Ionic compounds If the cation is monoatomic- Name the monoatomicmetal (cation) just write the name. I If the cation is polyatomic- name it polyatomicI If the anion is monoatomic- name it but monoatomicchange the ending to -ide I If the anion is poly atomic- just name it atomicI practice I More Naming 11 Ionic Compounds Have to know what ions they form off table, polyatomic, or figure it out I CaS I K2S I I I I I I I I I I I Ionic Compounds Fe2(C2O4) MgO MnO KMnO4 NH4NO3 Hg2Cl2 Cr2O3 AlPO4 K2SO4 I FeS I CoI3 Ionic Compounds KClO4 I NaClO3 I YBrO2 I Cr(ClO)6 I I Naming Covalent Compounds Two words, with prefixes I Prefixes tell you how many. I mono, di, tri, tetra, penta, hexa, septa, nona, deca I First element whole name with the appropriate prefix, except mono I Second element, -ide ending with appropriate prefix I Practice Naming Covalent Compounds CO2 CO I CCl4 I I I I Writing Formulas Two sets of rules, ionic and covalent To decide which to use, decide what the first word is. I If is a metal or polyatomic use ionic. I If it is a non-metal use covalent non- N2O4 I XeF6 I N4O4 I P2O10 I 12 Ionic Formulas Charges must add up to zero get charges from table, name of metal ion, or memorized from the list I use parenthesis to indicate multiple polyatomics I I I I Ionic Formulas Sodium nitride sodiumsodium- Na is always +1 I nitride - ide tells you it comes from the table I nitride is N-3 Ionic Formulas Sodium nitride I sodium- Na is always +1 sodiumI nitride - ide tells you it comes from the table I nitride is N-3 I doesn't add up to zero I I Ionic Formulas Sodium nitride I sodium- Na is always +1 sodiumI nitride - ide tells you it comes from the table I nitride is N-3 I doesn't add up to zero I Need 3 Na Na+1 N-3 Na+1 N-3 Na3N Ionic Compounds Sodium sulfite calcium iodide I Lead (II) oxide I Lead (IV) oxide I Mercury (I) sulfide I Barium chromate I Aluminum hydrogen sulfate I Cerium (IV) nitrite I I I Covalent compounds The name tells you how to write the formula I duh I Sulfur dioxide I diflourine monoxide I nitrogen trichloride I diphosphorus pentoxide 13 Acids Substances that produce H+ ions when dissolved in water I All acids begin with H I Two types of acids I Oxyacids I non oxyacids I More Names and formulas Naming acids If the formula has oxygen in it I write the name of the anion, but change ate to -ic acid ite to -ous acid I Watch out for sulfuric and sulfurous sulfuric sulfurous I I Naming acids If the acid doesn't have oxygen I add the prefix hydrohydroI change the suffix -ide to -ic acid I HCl I H2S I HCN H2CrO4 I HMnO4 I HNO2 I Formulas for acids Backwards from names If it has hydro- in the name it has no oxygen hydroI anion ends in -ide I No hydro, anion ends in -ate or -ite I Write anion and add enough H to balance the charges. I I I I Formulas for acids hydrofluoric acid dichromic acid I carbonic acid I hydrophosphoric acid I hypofluorous acid I perchloric acid I phosphorous acid 14 Hydrates Some salts trap water crystals when they form crystals I these are hydrates. I Both the name and the formula needs to indicate how many water molecules are trapped I In the name we add the word hydrate with a prefix that tells us how many water molecules I I Hydrates In the formula you put a dot and then write the number of molecules. I Calcium chloride dihydrate = CaCl222 I Chromium (III) nitrate hexahydrate = Cr(NO3)3 6H2O 15 ...
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This note was uploaded on 09/28/2009 for the course CHEM 102 taught by Professor Freeman during the Spring '08 term at South Carolina.

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