Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyHewitt/Suchocki/HewittConceptual Physical ScienceFourth EditionChapter 15:HOW ATOMS BOND AND MOLECULES ATTRACTCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyThis lecture will help you understand:• Electron-Dot Structures• The Formation of Ions• Ionic Bonds• Metallic Bonds• Covalent Bonds• Polar Covalent Bonds• Molecular Polarity• Molecular AttractionsCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley• Atoms bond together through their electrons. To learn about bonding, therefore, we need to know something about how the electrons within an atom are organized.• Electrons behave as though they are contained within a series of seven concentric shells.Electron-Dot StructuresCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyThe numbers indicate the maximum number of electrons each shell may contain.Note:This is a “conceptual model” and not a representation of what an atom “looks like.”Electron-Dot StructuresRather, it helps us to understand how the electrons within atoms behave.Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyThe shells are more easily drawn in two dimensions.Each atom has its own configuration of electrons. Elements in the same group have similar configurations, which is why they have similar properties.Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley• Valence electrons: Electrons in the outermost shell of an atom. These are the ones that can participate in chemical bonding.• Electron-dot structure: A notation showing the valence electrons surrounding the atomic symbol.Electron-Dot StructuresCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyIn class activity 1• Draw the dot diagram for sodium and chlorine ATOMSCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyFor heavier atoms, some valence electrons are more available than others. Krypton, for example, has 18 valence electrons, but only eight of these are typically shown within an electron-dot structure. These are the eight that extend farthest away from the nucleus.Special NoteKrCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyNote that elements within the same group have the same electron-dot structure. Electron-Dot StructuresCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleySodium, Na, atomic number 11, has only one valence electron. Upon losing this electron, what other atom in the periodic table does the sodium thus resemble?A. Neon, Ne, atomic number 10B. Magnesium, Mg, atomic number 12C. Lithium, Li, atomic number 3D. Sodium can only resemble sodium.Explanation:With 10 electrons, the sodium has enough electrons to fill the first and second shells, just like neon, Ne. Electron-Dot StructuresCHECK YOUR ANSWERCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyThe Formation of Ions• Ion: An atom that has lost or gained one or more electrons.Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyThe Formation of Ions• Ion: An atom that has lost or gained one or more electrons.Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley• Molecular ion: Typically formed by the loss or gain of a hydrogen ion, H+.HOHH+Water Hydrogen ionThe Formation of IonsCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley• Molecular ion: Typically formed by the loss or gain of a hydrogen ion, H+.HOHH+Hydronium ion, H3O+The Formation of IonsCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyIonic Bonds• Ion: An atom that has lost or gained one or more electrons.• Ionic Bond: The electrical force of attraction between oppositely charged ions.Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyIn class activity 2• What is the charge of an ion that is formed from a magnesium atom?• Why does it have this sign and amount of charge?Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley• Ion: An atom that has lost or gained one or more electrons.• Ionic Bond: The electrical force of attraction between oppositely charged ions.Na+F-Ionic BondsCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley• Ion: An atom that has lost or gained one or more electrons.• Ionic Bond: The electrical force of attraction between oppositely charged ions.Na+F-Ionic BondsCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyIn class activity 3• Draw the dot diagrams of sodium and chlorine IONSCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyA. AlOB. Al3O2C. Al2O3D. Al6O6What is the chemical formula for a compound made of aluminum ions, Al3+, and oxygen ions, O2–?Ionic BondsCHECK YOUR ANSWERCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyA. MgOB. Mg2O2C. Mg4O4D. Any of the aboveWhat is the chemical formula for a compound made of magnesium ions, Mg2+, and oxygen ions, O2–?Explanation:The chemical formula is used to show the ratio by which atoms combine. By convention, the lowest numbers are preferred, so 1:1 is used rather than 2:2. The numeral 1, however, is implied when no subscript is written. Ionic BondsCHECK YOUR ANSWERCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyIn class activity 4• Is the change from sodium and chlorine a physical or a chemical change?Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyIn class activity 5• Write the chemical formula of the ionic compound calcium fluorideCopyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyMetallic Bonds• Outer electrons in metal atoms are held only weakly by the nucleus.• This weak attraction allows the electrons to move about quite freely.• This mobility of electrons accounts for many metallic properties.Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyMetallic Bonds• An alloy is a mixture of metallic elements.Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-WesleyCovalent Bonds• The type of electrical attraction in which atoms are held together by their mutual
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