CHM1045 Lecture 5 Outline of Last Lecture I Daltons Atomic Theory II Cathode Ray Tube III Millikan s Experiment IV Rutherford s Experiment V Chadwick s Experiment VI Atomic Mass Isotopes VII Molecules VIII Ions Outline of Current Lecture I Formulas II Ionic Compounds III Chemical Nomenclature IV Need to Memorize Current Lecture Formulas Molecular Formula Exact numbers of atoms in each element Empirical Formula shows the simplest whole number ratio of the atoms in a substance Example 1 Write the molecular formula of methanol an organic solvent and antifreeze from its ball and stick model shown below H C H H O H CH4O Ionic Compounds Ionic compounds consist of a combination of cations and anions The formula is usually the same as the empirical formula The sum of the charges on the cation s and anion s in each formula unit must equal zero The most reactive metals and the most reactive nonmetals combine to form ionic compounds 2x 3 6 Al2 O3 3x 2 6 Al3 O2Example 2 Write the formula of magnesium nitride containing the Mg2 and N3 ions Mg2 N3Mg3N2 Chemical Nomenclature Ionic Compounds Often a metal nonmetal Anion nonmetal add ide to element name BaCl2 barium chloride K2O potassium oxide Mg OH 2 magnesium hydroxide KNO3 potassium nitrate Transition metal ionic compounds indicate charge on metal with Roman numerals FeCl2 2 Cl 2 so Fe is 2 iron II chloride FeCl3 3 Cl 3 so Fe is 3 iron III chloride Cr2S3 3 S 2 6 so Cr is 3 6 2 chromium III sulfide Need to Memorize Ammonium NH 4 Chromate CrO24 Dihydrogen Phosphate H2PO24 Hydrogen phosphate HPO24 Hydroxide OHPhosphate PO3 4 Hydroxide OHNitrate NO 3 Nitrite NO 2 Permangate MnO 4 Carbonate CO2 3 Cyanide CNHydrogen carbonate or bicarbonate Cr2O2 7 Hydrogen sulfate or bisulfate HSO 4 Chlorate ClO 3 dichromate CrO2 7 Phosphate PO3 4 Sulfate SO2 4 Sulfite SO2 3 Thiocyanate SCN Example 1 Name the following compounds a Cu NO3 2 b KH2PO4 c NH4ClO3 a Copper II Nitrate b Potassium dihydrogen Phosphate c Ammonium Chlorate Example2 Write chemical formulas for the following compounds a mercury II nitrite b cesium sulfide c calcium phosphate a Hg2 NO 2 Hg NO2 2 b Cs1 S2Cs2S c Ca2 PO43 Ca3 PO4 2
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