Atomic Bonding and MoleculesChapter 15Bonding of atoms makes molecules• The Formation of Ions and Ionic Bonds• Types of bonds– Metallic Bonds– Covalent Bonds– Polar Covalent Bonds• Molecular Polarity and Molecular AttractionsCauses of bonding• Atoms bond together through their electrons• Electrons behave as though they are contained within a series of seven concentric shells• Outer shell electrons interact with electrons of other atoms• These are the VALENCE electronsElectron Shells• Maximum number of electrons in each shell is shown• Inner shell fills up before next shell begins to get electrons• Full shells are most stableFull electron shells• Outer electron shells of noble gases are fullSodium Ion Formation• Ion: An atom that has lost or gained one or more electronsPeriodic tableElectrons shells in periodic table• First three periodsElectron Dot Structure• A notation showing only the valence electrons surrounding the atomic symbolValence Electron dot structure for elements not in transition metal groupsIon• An atom, molecule, or compound with a different number of protons and electrons• More protons: positive CAT ION–THE t looks like a plus sign…• More electrons: negative AN ION– Negative has an N in the prefix• Both are all one word: anion, cationIon formation• Lose electrons– more protons than electrons– positive charge• Gain electrons– More electrons than protons– Negative charge• More than one can be lost or gained• Determine by position in periodic tableElectron dot structure patternIonic Bonds• Electrical force of attraction between oppositely charged ionsIonic Bond Ratios• Compounds form in ratios to neutralize chargesMolecular Ions• Typically formed by the loss or gain of a hydrogen ion, H+HOHH+Hydronium ion, H3O+H+Water Hydrogen ionGroups of atoms forming ions• Molecular ions• Bonds within group are covalentMetallic Bonds• Nucleus of metal atoms only weakly hold outer electrons• Weak attraction allows the electrons to move from one atom to another quite freelyMetallic PropertiesMobility of electrons results in many properties of metals• Conductive—electrons move freely• Shiny—electrons vibrate and reflect light• Malleable—can move with respect to one another without breaking because electrons in constant motion• Alloys—electrons shared between unlike types of metal atomsMetallic Alloys• An alloy is a mixture of metallic elements.Metal Ores• Few metals naturally occur as elements– Gold, copper, mercury• Most occur as oxides and sulfides– Ionic compounds– Concentrations of these are ORECovalent Bonds• Atoms are held together by their mutual attraction for shared electrons• There are two electrons within a single covalent bondCovalent Bond Diagrams• The covalent bond is represented using a straight lineF — FF FCovalent Water• The number of covalent bonds an atom can form equals its number of unpaired valence electronsCovalent Ammonia• The number of covalent bonds an atom can form equals its number of unpaired valence electronsCovalent Methane• The number of covalent bonds an atom can form equals its number of unpaired valence electronsMultiple covalent bonds• are possible if atom has more than one unpaired valence electronNonpolar Covalent Bonds• Electrons are shared evenly when the two atoms are the same elementPolar Covalent Bonds• Shared unevenly when the bonded atoms are different elementsPolar covalent bonds• Closer together on the periodic table, less polar bond• Further apart on the periodic table, more polar bond• Molecules are called ‘dipoles’• Ionic bonds are extremely polar—but not
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