Chapter FiveOutlineGoalsGoals Contd.5. 1 Covalent BondsSlide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 145.2 Covalent Bonds and the Periodic TableSlide 16Slide 17Slide 185.3 Multiple Covalent BondsSlide 20Slide 21Slide 22Slide 235.4 Coordinate Covalent BondsSlide 255.5 Molecular Formulas and Lewis StructuresSlide 275.6 Drawing Lewis StructuresSlide 29Slide 305.7 The Shapes of MoleculesSlide 32Slide 33Slide 345.8 Polar Covalent Bonds and ElectronegativitySlide 36Slide 37Slide 38Slide 395.9 Polar MoleculesSlide 41Slide 425.10 Naming Binary Molecular CompoundsSlide 44Slide 455.11 Characteristics of Molecular CompoundsChapter SummarySlide 48Chapter Summary Contd.Key WordsSlide 51Chapter FiveMolecular CompoundsFundamentals of General, Organic and Biological Chemistry 6th EditionJames E. MayhughCopyright © 2010 Pearson Education, Inc.Copyright © 2010 Pearson Education, Inc.Chapter Five2Outline►5.1 Covalent Bonds►5.2 Covalent Bonds and the Periodic Table►5.3 Multiple Covalent Bonds►5.4 Coordinate Covalent Bonds►5.5 Molecular Formulas and Lewis Structures►5.6 Drawing Lewis Structures►5.7 The Shapes of Molecules►5.8 Polar Covalent Bonds and Electronegativity►5.9 Polar Molecules►5.10 Naming Binary Molecular Compounds►5.11 Characteristics of Molecular CompoundsCopyright © 2010 Pearson Education, Inc.Chapter Five3Goals►1. What is a covalent bond? Be able to describe the nature of covalent bonds and how they are formed.►2. How does the octet rule apply to covalent bond formation? Be able to use the octet rule to predict the numbers of covalent bonds formed by common main group elements.►3. How are molecular compounds represented? Be able to interpret molecular formulas and draw Lewis structures for molecules.Copyright © 2010 Pearson Education, Inc.Chapter Five4Goals Contd.►4. What is the influence of valence-shell electrons on molecular shape? Be able to use Lewis structures to predict molecular geometry.►5. When are bonds and molecules polar? Be able to use electronegativity and molecular geometry to predict bond and molecular polarity.►6. What are the major differences between ionic and molecular compounds? Be able to compare the structures, compositions, and properties of ionic and molecular compounds.Copyright © 2010 Pearson Education, Inc.Chapter Five55. 1 Covalent Bonds►The bond formed when atoms share electrons is called a covalent bond. (Unlike ionic bonds, which involve the complete transfer of electrons). ►A group of atoms held together by covalent bonds is called a molecule. ►Main group elements can obtain completed outer subshells with eight valence electrons (or two for hydrogen), so that they have a noble gas electron configuration, by sharing an appropriate number of electrons in covalent bonds.Copyright © 2010 Pearson Education, Inc.Chapter Five6A single molecule of water contains two hydrogen atoms and one oxygen atom covalently bonded to one another. We might visualize a water molecule using a space-filling model as shown here:Copyright © 2010 Pearson Education, Inc.Chapter Five7►When two atoms come together, electrical interactions occur.► Some of these interactions are repulsive—the two positively charged nuclei repel each other and the negatively charged electrons repel each other.►Other interactions, however, are attractive—each nucleus attracts the electrons and each electron attracts both nuclei. ►When the attractive forces are stronger than the repulsive forces, a covalent bond is formed and the atoms stay together.Copyright © 2010 Pearson Education, Inc.Chapter Five8When the nucleus–electron attractions (blue arrows) are greater than the nucleus–nucleus and electron–electron repulsions (red arrows), the result is a net attractive force that holds the atoms together to form a molecule.Copyright © 2010 Pearson Education, Inc.Chapter Five9►Covalent bond formation in H2 can be visualized by imagining that the two spherical 1s atomic orbitals blend together and overlap to give an egg-shaped molecular orbital. ►Both atoms share the two valence electrons and the stability of the closed shell electron configuration. ►The shared pair of electrons in a covalent bond can be represented as a line between atoms.Copyright © 2010 Pearson Education, Inc.Chapter Five10►If atoms are too far apart, attractions are weak and no bonding occurs. ►If atoms are too close, strong repulsions occur. ►When atoms are optimally separated, the energy is at a minimum. ►The distance between nuclei at this minimum energy point is called the bond length.Copyright © 2010 Pearson Education, Inc.Chapter Five11A graph of potential energy versus internuclear distance for the H2 molecule.Copyright © 2010 Pearson Education, Inc.Chapter Five12►An individual Cl atom has 7 valence electrons. 6 of these are paired and the 7th is unpaired.►When two Cl atoms approach each other, the unpaired 3p electrons are shared by both atoms in a covalent bond. ►Each Cl atom in the molecule now “owns” six outer-shell electrons and “shares” two more, giving each a valence shell octet like that of the noble gas Ar.Copyright © 2010 Pearson Education, Inc.Chapter Five13►Bond formation in Cl2 can also be pictured as the overlap of the two 3p atomic orbitals containing the single unpaired electrons.► The molecular orbital formed creates a region of high electron density between the two nuclei.Copyright © 2010 Pearson Education, Inc.Chapter Five14►In addition to H2 and Cl2, five other elements always exist as diatomic (two-atom) molecules. ►N2 and O2 are colorless, odorless, nontoxic gases. F2 is a pale yellow, highly reactive gas; Br2 is a dark red, toxic liquid; and I2 is a violet, crystalline solid.Copyright © 2010 Pearson Education, Inc.Chapter Five155.2 Covalent Bonds and the Periodic Table►Covalent bonds can form between unlike atoms making possible a vast number of molecular compounds: compounds that consist of molecules rather than ions.► Water molecules consist of two hydrogen atoms joined by covalent bonds to an oxygen atom, ammonia molecules consist of three hydrogen atoms covalently bonded to a nitrogen atom, and methane molecules consist of four hydrogen atoms covalently bonded to a carbon atom.Copyright © 2010 Pearson Education, Inc.Chapter Five16Note that in all these examples, each atom shares enough electrons to achieve a noble gas configuration: two electrons for hydrogen, and