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Atoms, Molecules, and Ions Old Dead Greek Guys (400 B.C.) Democritus— matter is made up of indivisible particles Aristotle—matter is continuous 2.1 Antoine Lavoisier (1789) The Father of Modern Chemistry Law of Conservation of Mass Mass is neither created nor destroyed Discovered 33 elements 2.2 M. & Mme. Lavoisier 2.2 Joseph Louis Proust (1800ish) Law of Definite Proportion A given cmpd always contains exactly the same proportion of elements by mass 2.2 Dalton’s Atomic Theory (1808) 1. Each element is made up of tiny particles called atoms 2. The atoms of a given element are identical, that atoms of different elements are different 3. Cmpds are formed when atoms of diff. elements combine, a given cmpd has same # & types of atoms 4. Rxns involve reorganization of atoms 2.3 John Dalton 2.3 Dalton’s Model of the Atom Called the Marble Model 2.3 J. J. Thomson 2.4 J. J. Thomson (1898-1903) Studied cathode ray tubes “ray” was a stream of negatively charged particles, called electrons He get credit for discovering electrons 2.4 Cathode Ray Tube (CRT) Direction of electron travel Cathode: - electrode Anode: + electrode 2.4 J. J. Thomson Used the CRT to measure the charge to mass ratio of an electron e/m = -1.76 x 108 C/g e = charge on e- in coulombs (C) m = e-’s mass in grams (g) 2.4 Plum Pudding Model 2.4 Millikan’s Oil Drop (1909) Did an experiment with charged oil drops Used e/m & the magnitude of the e- charge to calc the mass of an e Mass of e- = 9.11 x 10-31 kg 2.4 Millikan’s Oil Drop 2.4 Radioactivity Henri Becquerel Accidentally Discovered Radioactivity Marie and Pierre Curie Studied radioactivity and discovered other radioactive elements. 2.4 Becquerel (1896) Discovered radioactivity by accidentally placing a uranium “rock” onto a photographic plate 2.4 Radioactivity Spontaneous emission of radiation from an element a radiation: attracted to neg. plate Particles w/ 2+ charge b radiation: attracted to pos. plate High-speed electrons g radiation: no attraction Not particles, similar to X-rays 2.4 a g b Earnest Rutherford Gold foil experiment, also called the a-particle experiment Discovered the nucleus: center has a positive charge and most of the atoms mass Electron move around the nucleus at a distance that is large relative to the nuclear radius a-particle experiment a-particles were shot at a sheet of gold foil Most particles went straight through representing that atoms are mostly empty space Some particles were deflected off of the gold foil showing that there was in fact a dense nucleus in the center of an atom Rutherford Model Niels Bohr Bohr Model The e-’s orbit the nucleus of an atom in specific pathways Also called the solar system model since it mimics how the planets orbit the sun Bohr Model Structure of the Atom Particle Symbol Charge Mass (amu) Location Proton p Positive 1 Inside Neutron n Neutral 1 Inside Electron e- negative 0 Outside Atomic Number The # of protons in an atom Also gives the # of e-’s since an atom is electrically neutral For every proton there is an e What makes one element different from another 50 Sn Tin Ion When an atom gains or loses one or more e-’s Gain of e- neg. charge Loss of e- pos. charge Ion Problems 1. How many protons, neutrons, and 25 2 electrons are present in the 12 Mg ion? 2. Write a chemical symbol for the ion with 74 p and 68 e-. Ion Problems - Answers 1. How many protons, neutrons, and 25 2 electrons are present in the 12 Mg ion? 12 p, 13 n, 10 e2. Write a chemical symbol for the ion with 74 p, 110 n, and 68 e-. 184 74 W 6 . Mass Number The number of protons + neutrons Protons and neutrons are called nucleons Isotopes Atoms that have the same # of protons but a different number of neutrons Major diff between two isotopes is their mass Example: Carbon-12: 6 protons, 6 neutrons, 6 electrons Carbon-14: 6 protons, 8 neutrons, 6 electrons Chemical Symbol Mass # (M) 141 56 Ba Atomic # (Z) 2 Charge Chemical Symbols # of protons = Z # of neutrons = M – Z # of electrons = Z – charge Problems 1. How many p, n, & e are present in the 59 Ni2 ion? 28 Write the chemical symbol for the ion with 53 p, 74 n, and 54 e-. Problems - Answers 1. How many p, n, & e- are 2 ion? present in the59 28 Ni 28 p, 31 n, & 26 e- 2. Write the chemical symbol for the ion with 53 p, 74 n, and 54 e-. Symbol = 127 53 I Atomic Mass Atomic mass is the average mass of all the isotopes of the element Weighted by abundances of isotopes Based on Carbon-12 isotope: def’n of atomic mass unit READ IT!!!! READ IT!!!! Naming Ionic Compounds Use your common ion chart The common ions must be memorized! You will NOT get to use the chart on any test. Monatomic Cations Same name as the element Group IA +1 ions Group IIA +2 ions + Na = soduim Monatomic Cations Transition metals will form more than one cation Add roman numerals to name for the charge Fe2+ iron(II) Fe3+ iron(III) Monatomic Anions Name ends in –ide Cl- = Chlorine Chloride Group VIIA -1 ions Group VIA -2 ions Polyatomic Ions Get their names from the common ion chart SO42- = sulfate PO43- = phosphate Sample Problems What are the formulas for 1. sodium bromide 2. copper(II) phosphate Sample Problems - Answers What are the formulas for 1. sodium bromide Na+ Br- NaBr 2. copper(II) phosphate Cu2+ PO43- Cu3(PO4)2 Sample Problems What are the names for 1. NaC2H3O2 2. Fe(OH)2 Sample Problems - Answers What are the names for 1. NaC2H3O2 Na+ C2H3O2- sodium acetate 2. Fe(OH)2 Fe2+ OH- Iron(II) hydroxide Oxyanions Series of anions with varying #’s of oxygen atoms Smaller # of O’s: -ite Larger # of O’s: -ate Ex: SO32- sulfite SO42- sulfate More than 2 oxyanions: ClO ClO2- ClO3 ClO4- hypochlorite chlorite chlorate perchlorate Sample Problems What are the formulas for 1. cesium perchlorate 2. sodium hydrogen carbonate Sample Problems - Answers What are the formulas for 1. cesium perchlorate Cs+ ClO4- CsClO4 2. sodium hydrogen carbonate Na+ HCO3- NaHCO3 Sample Problems What are the names for 1. Fe(NO3)3 2. KH2PO4 Sample Problems - Answers What are the names for 1. Fe(NO3)3 Fe3+ NO3- iron(III) nitrate 2. KH2PO4 K+ H2PO4- potassium hydrogen phosphate Naming Covalent Cmpds Numerical prefixes are used Common ion chart is not used Numerical Prefixes 1. mono2. di3. tri4. tetra5. penta- 6. hexa7. hepta8. octa9. nona10. deca- Naming Covalent Cmpds If there is only one atom of the first element it doesn’t get a prefix Naming Covalent Cmpds Element furthest to the right in periodic table (or the most electronegative element) is named 2nd and its name ends in -ide Sample Problems What are the formulas for 1. boron trifluoride 2. diphosphorous pentoxide Sample Problems - Answers What are the formulas for boron trifluoride 1. BF3 2. diphosphorous pentoxide P2O5 Sample Problems What are the names for 1. SiO2 2. CO Sample Problems - Answers What are the names for 1. SiO2 Silicon dioxide 2. CO Carbon monoxide Acids Give off protons (H+) in water Acids ionize into H+ ions and an anion A HA H+ + A HCl H+ + Cl- Acids w/o oxygens Prefix: hydro Suffix: –ic acid HCl: hydrochloric acid H2S: hydrosulfuric acid Acids w/ Oxygen in Anion -ate to –ic acid 2. -ite to –ous acid 1. Acid Anion Name Acid Name H2SO4 SO42Sulfate SO32Sulfite Sulfuric acid H2SO3 Sulfurous acid Oxyacids Acid Anion Name HClO Hypochlorite Hypochlorous acid HClO2 Chlorite Chlorous acid HClO3 Chlorate Chloric acid HClO4 Perchlorate Perchloric acid