Chapter 6 Compounds and Their Bonds PDF

Chapter 6 Compounds and Their Bonds Covalent Compounds General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 80  Covalent Bonds Molecular compounds form when atoms of two or more nonmetals share electrons and form a cov...

Chapter 6 Compounds and Their Bonds Covalent Compounds General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 80  Covalent Bonds Molecular compounds form when atoms of two or more nonmetals share electrons and form a covalent bond. valence electrons are shared by nonmetal atoms to achieve stability. A molecule forms when two or more atoms share electrons. Covalent Bonds Covalent bonds form  when atoms share electrons to complete octets  between two nonmetal atoms from from Groups 4A(14), 5A(15), 6A(16), and 7A(17) General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 82 Diatomic Elements  These elements share electrons to form diatomic, covalent molecules. Learning Check What is the name of each of the following diatomic molecules? H2 Hydrogen N2 Nitrogen Cl2 Chlorine O2 Oxygen I2 Iodine General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 84 Carbon Forms 4 Covalent Bonds In a methane (CH4) molecule,  the central C atom shares 4 electrons to attain an octet  each H atom shares 1 electron with the carbon atom to become stable like He General, Organic, and Biological Chemistry 85 Number of Covalent Bonds The number of covalent bonds can be determined from the number of electrons needed to complete an octet. Single and Multiple Bonds  In a single bond, one pair of electrons is shared.  In a double bond, two pairs of electrons are shared.  In a triple bond, three pairs of electrons are shared. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 87  Names and Formulas, Molecular Compounds When naming a molecular compound, the first nonmetal in the formula is named by its element name. second nonmetal is named using the first syllable of the name followed by ide. When a subscript indicates two or more atoms of an element, a prefix is shown in front of its name. Chapter 6 Compounds and Their Bonds Naming and Writing Covalent Formulas NO nitrogen oxide NO2 nitrogen dioxide N2O4 dinitrogen tetroxide General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 89 Names of Covalent Compounds Prefixes are used  in the names of covalent compounds  because two nonmetals can form two or more different compounds Examples of compounds of N and O: NO nitrogen oxide NO2 nitrogen dioxide N2O dinitrogen oxide N2O4 dinitrogen tetroxide N2O5 dinitrogen pentoxide General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 90  Names and Formulas, Molecular Compounds Several compounds may be formed from the same two nonmetals: CO2 = carbon dioxide CO = carbon monoxide The number of oxygen atoms present is indicated by the prefix. When the vowels o and o or a and o appear together, the first vowel is omitted. NO = nitrogen monoxide, Common Molecular Compounds Guide to Naming Covalent Compounds with Two Nonmetals General, Organic, and Biological Chemistry 93  Study Check Name the molecular compound B2O3. Symbol of the Element B O ANALYZE THE Name boron oxide PROBLEM Subscript 2 3 Prefix di tri STEP 1 Name the first nonmetal by its element name. In B2O3, the first nonmetal (B) is boron. STEP 2 Name the second nonmetal by using the first name followed by ide. The name of the second nonmetal (O) is oxide. STEP 3 Add prefixes to indicate the number of atoms (subscripts). The first nonmetal (B) has the subscript of 2, which is shown as the prefix di and subscript of 3 for the O atoms is shown as the prefix tri. The name of B2O3 is diboron trioxide  Naming Covalent Compounds (Continued: more examples) Example1: What is the name of SO3? The first nonmetal is S sulfur. The second nonmetal is O, named oxide. Subscript 3(for O) is shown as the prefix tri. SO3 → sulfur trioxide The subscript 1(for S) or mono is understood Example 2: Name P4S3 The first nonmetal P is phosphorus. The second nonmetal S is sulfide. The subscript 4 (of P) is shown as tetra. The subscript 3(of O) is shown as tri. P4S3 → tetraphosphorus trisulfide Guide to Writing Formulas for Covalent Compounds General, Organic, and Biological Chemistry 96 Writing Formulas of Covalent Compounds Write the formula for carbon disulfide. Elements are C and S No prefix for carbon means 1 C Prefix di = 2 Formula: CS2 General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 97  Learning Check Write the correct formula for each of the following: A. phosphorus 1P , penta = 5Cl PCl5 pentachloride B. dinitrogen trioxide di = 2N, tri = 3 O N2O3 C. sulfur hexafluoride 1S , hexa = 6F SF6 General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 98  Compounds, Ionic or Covalent? A compound is usually ionic if the first element in the formula or the name is a metal or the polyatomic ion NH4+. K2O: K is a metal; the compound is ionic. potassium oxide covalent if the first element in the formula is a nonmetal. N2O: N is a nonmetal; the compound is covalent. dinitrogen oxide  Study Check & Solution Identify each compound as ionic or covalent and give its correct name. A. SO3 covalent – sulfur trioxide B. BaCl2 ionic – barium chloride C. (NH4)3PO3 ionic – ammonium phosphite D. Cu2CO3 ionic – copper(I) carbonate E. N2O4 covalent – dinitrogen tetroxide Flowchart, Naming Compounds