Name Date Class COVALENT BONDING. Standard Curriculum Core content Extension topics. SECTION 16.1 THE NATURE OF COVALENT BONDING (pages )

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1 16 CVALENT BNDING Conceptual Curriculum Concrete concepts More abstract concepts or math/problem-solving Standard Curriculum Core content Extension topics onors Curriculum Core honors content ptions to accelerate SECTIN 16.1 TE NATURE F CVALENT BNDING (pages ) This section uses electron dot structures to show the formation of single, double, and triple covalent bonds. It also describes and gives examples of coordinate covalent bonding, resonance structures, and exceptions to the octet rule. Single Covalent Bonds (pages ) 1. What is a covalent bond? A covalent bond is a bond formed when two atoms share electrons. 2. Is the following sentence or false? A shared pair of electrons is represented by a double dash. false 3. Structural formulas show the arrangement of atoms in molecules and polyatomic ions. 4. What is the octet rule of covalent bonding? Sharing of electrons occurs if the atoms involved acquire the electron configurations of noble gases, which usually contain eight valence electrons (an octet). 5. Use the electron dot diagram below. Circle each unshared pair of electrons in a water molecule. Prentice-all, Inc. 6. Complete the electron dot structure for each molecule. Each molecule contains only single covalent bonds. Br F C a. BrF b. 2 2 c. C 4 Guided Reading and Study Workbook 147

2 CAPTER 16, Covalent Bonding (continued) Double and Triple Covalent Bonds (pages ) 7. A chemical bond formed when atoms share two pairs of electrons is called a(n) double covalent bond. 8. Use Figure 16.5 on page 442. ow many covalent bonds are in the nitrogen molecule? three 9. Is the following sentence or false? All diatomic molecules contain double bonds. false Coordinate Covalent Bonds (pages ) 10. What is a coordinate covalent bond? It is a covalent bond in which one atom contributes both bonding electrons. 11. Look at Table 16.2 on page 445. Which three nitrogen compounds contain coordinate covalent bonds? nitrogen dioxide, dinitrogen tetroxide, and nitrous oxide 12. Complete the electron dot structure of the chlorate ion (Cl 3 ) by filling in the bonds and unpaired electrons. Cl Bond Dissociation Energies (pages ) 13. What is bond dissociation energy? Bond dissociation energy is the total energy required to break the bond between two covalently bonded atoms. 14. Is the following sentence or false? Molecules with high bond dissociation energies are relatively unreactive. Prentice-all, Inc. 15. Use Table 16.3 on page 448. What are the bond energies for the following covalent bonds? a. C kj/mol b. C N 305 kj/mol c. 142 kj/mol 148 Guided Reading and Study Workbook

3 16. Circle the letter of the correct answer. ow many kilojoules are required to dissociate all the bonds in 0.25 mole of carbon dioxide (C 2 )? a. 736 kj b. 368 kj c. 184 kj d kj Resonance (page 449) 17. What are resonance structures? They are structures that occur when it is possible to write two or more valid electron dot formulas that have the same number of electron pairs for a molecule or ion. 18. The actual bonding in ozone is a hybrid of the extremes represented by its resonance structures. Exceptions to the ctet Rule (pages ) 19. Why does N 2 not follow the octet rule? There is an unpaired electron present in both possible resonance structures. 20. xygen molecules are paramagnetic because they contain unpaired electrons. SECTIN 16.2 BNDING TERIES (pages ) This section describes the molecular orbital theory of covalent bonding, including orbital hybridization. It also explains the use of VSEPR theory to predict the shapes of some molecules. Molecular rbitals (pages ) 1. What is a molecular orbital? When two atoms combine, their atomic orbitals overlap to produce orbitals that apply to the entire molecule. Prentice-all, Inc. 2. What two molecular orbitals are created when two atomic orbitals overlap? a. a bonding orbital b. an antibonding orbital 3. Is the following sentence or false? Electrons fill the antibonding molecular orbital first to produce a stable covalent bond. false 4. When two s atomic orbitals combine, the molecular orbital formed is called a(n) sigma bond. 5. For a stable covalent bond to form, the attractions between the nuclei and the electrons must be stronger than the repulsions. 6. Circle the letter of each type of covalent bond that can be formed when p atomic orbitals overlap. a. pi b. beta c. sigma d. alpha Guided Reading and Study Workbook 149

4 CAPTER 16, Covalent Bonding (continued) VSEPR Theory (pages ) 7. What is VSEPR theory? The valence-shell electron-pair repulsion theory states that because electron pairs repel, molecular shape adjusts so the valence-electron pairs are as far apart as possible. 8. When the central atom of a molecule has unshared electrons, the bond angles will be smaller than when all the central atom s electrons are shared. 9. What is the bond angle in carbon dioxide? Why? The bond angle is 180 because the carbon atom has no unshared electron pairs. 10. What are the names of these common molecular shapes? Linear triatomic Pyramidal Bent triatomic Trigonal planar Tetrahedral Trigonal bipyramidal ybrid rbitals (pages ) 11. What is orbital hybridization? rbital hybridization occurs when atomic orbitals mix to form the same total number of equivalent hybrid orbitals. 12. Is the following sentence or false? rbital hybridization theory can describe both the shape and bonding of molecules. Prentice-all, Inc. Match the hybrid orbitals formed by carbon with the carbon compound in which they are found. c 13. sp 3 b 14. sp 2 a 15. sp a. ethyne b. ethene c. methane 150 Guided Reading and Study Workbook

5 Reading Skill Practice You can increase your understanding of what you have read by making comparisons. A compare/contrast table can help you do this. n a separate sheet of paper, draw a table to compare the three types of hybrid orbitals as explained on pages 458 and 459. The three heads for the rows should be sp, sp 2, and sp 3. Then list the characteristics that will form the basis of your comparison above each column. The column heads should be Number of ybrid rbitals, Component rbitals, Number of Bonds, and Bond Angle. Students tables should include the basic information about the three types of hybrid orbitals contained on pages SECTIN 16.3 PLAR BNDS AND MLECULES (pages ) This section explains the use of electronegativity values to classify a bond as nonpolar covalent, polar covalent, or ionic. It also names and describes the weak attractive forces that hold groups of molecules together. Bond Polarity (pages ) 1. Is the following statement or false? Covalent bonds differ in the way electrons are shared by the bonded atoms, depending on the kind and number of atoms joined together. 2. Describe how electrons are shared in each type of bond. Write equally or unequally. a. Nonpolar bond equally b. Polar bond unequally Prentice-all, Inc. 3. Why does the chlorine atom in hydrogen chloride acquire a slightly negative charge? Chlorine has a higher electronegativity than hydrogen, and, therefore, attracts the bonding electrons slightly away from hydrogen. 4. What symbols are used to represent the charges on atoms in a polar covalent bond? The polarity of the bond? or ; JKL Match the electronegativity difference range with the most probable type of bond that will form. b d c a a. ionic b. nonpolar covalent c. very polar covalent d. moderately polar covalent Guided Reading and Study Workbook 151

6 CAPTER 16, Covalent Bonding (continued) Polar Molecules (pages ) 9. Circle the letter of each sentence that is about polar molecules. a. Some regions of a polar molecule are slightly negative and some are slightly positive. b. A molecule containing a polar bond is always polar. c. A molecule that has two poles is called a dipolar molecule. d. When polar molecules are placed in an electric field, they all line up with the same orientation in relation to the charged plates. 10. Are the following molecules polar or nonpolar? a. 2 polar c. N 3 polar b. C 2 nonpolar d. CCl nonpolar Attractions Between Molecules (pages ) 11. What causes the two types of van der Waals forces? Dispersion forces are caused by the motion of electrons. Dipole interactions are caused by the attractions between polar molecules. 12. Is the following sentence or false? Dispersion forces generally increase in strength as the number of electrons in a molecule increases. 13. The strongest of the intermolecular forces are hydrogen bonds. Intermolecular Attractions and Molecular Properties (pages ) 14. What determines the physical properties of a compound? The physical properties depend on the type of bonding in the compound. 15. Use Table 16.5 on page 465. Complete the following table comparing ionic and covalent compounds. Characteristic Ionic Compound Covalent Compound Prentice-all, Inc. Representative unit Physical state Melting point Solubility in water formula unit solid high usually high molecule solid, liquid, or gas low high to low 152 Guided Reading and Study Workbook