University:
Missouri State University
Course:
CHM 160 | General Chemistry I
Academic year:

2022
Views:

269

Pages:

19
Author:

helyettitycx1

Section 9.3: Naming and Writing Formulas for Molecular Compounds Read pages 268-270 Binary Molecular Compounds 68   A binary molecular compound is composed of two elements – both are nonmetals Binary molecular compounds do not contain ions – they are made of… molecules 69 Carbon and oxygen combine to form carbon monoxide (CO) and carbon dioxide (CO2), but these two invisible gases are very different. Sitting in a room with small amounts of CO2 in the air would not present any problems. If the same amount of CO were in the room, you could die of asphyxiation. A naming system that distinguishes between these two compounds is needed. Naming Binary Molecular Compounds 70 Use prefixes  The prefix in the name of a binary molecular compound tells how many atoms of each element are present in each molecule of the compound  Steps for Naming a Binary Molecular Compound 71 Confirm that the compound is a binary molecular compound. Name the elements in the order that they appear in the formula 1. 2. a. b. Use prefixes to indicate the number of each kind of atom. The name of the first element stays the same. The ending of the second element changes to –ide. Quick Example – Add it to your notes! 72 S2Br4 disulfur tetra bromide Special Rules 73  If there is only one atom of the first element in the formula, drop the mono- CCl4 is called carbon tetrachloride, NOT monocarbon tetrachloride.  If the element begins with a vowel, drop the vowel on the end of the prefix. Exceptions: Di- and Tri- CO is called carbon monoxide, NOT carbon monooxide. Naming Binary Molecular Compounds Example 1 74 N2O dinitrogen mon oxide Naming Binary Molecular Compounds Example 2 75 Cl2O8 dichlorine oct oxide Try It! 76  Write the names of the following binary molecular compounds: CBr4 2. N2H4 3. PCl5 4. S2F10 1. 1. 2. 3. 4. Carbon tetrabromide Dinitrogen tetrahydride Phosphorus pentachloride Disulfur decafluoride Writing Formulas for Binary Molecular Compounds 77  Use the prefixes in the name to tell you the subscript of each element in the formula. Then, write the correct symbols for the two elements with the appropriate subscripts. Writing Formulas for Binary Molecular Compounds Example 1 78 Dinitrogen trioxide N2O3 Writing Formulas for Binary Molecular Compounds Example 2 79 Iodine heptafluoride I F7 Try it! 80 a. b. c. d. Carbon disulfide Tribromine octoxide Silicon monocarbide Dihydrogen monoxide a. b. c. d. CS2 Br3O8 SiC H2O Ionic 81 Covalent That is a representative metal or transition metal with only 1 charge Name cation (name stays same) Name anion (ending in –ide) That is a transition metal with multiple possible charges Name cation (use roman numerals) Name anion (ending in –ide) Bonded to a polyatomic ion Name cation (see above) Name anion (polyatomic name) Name compound using prefixes Second element ends in -ide Quick Quiz Section 9.3 1. Which of the following compounds is named INCORRECTLY? 83 a. b. c. d. CS2, carbon disulfide BCl3, boron trichloride IF7, iodine heptafluoride PCl5, phosphorus hexachloride 2. Which of the following molecular compounds is named INCORRECTLY? 84 a. b. c. d. SbCl3, antimony trichloride C2O5, dicarbon pentoxide CF4, carbon tetrafluoride H3S, hydrogen sulfide 3. The correct formula for tetraphosphorus trisulfide is 85 a. b. c. d. P3S4 S3P4 P4S3 S4P3