Chapter 8 Chemical Bonding

Metals e 1 structures of ionic crystals q crystal

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Unformatted text preview: 1 Structures of Ionic Crystals q Crystal lattice is an arrangement of ions of Crystal opposite charge surrounding one another in three dimensions. in q Several ways of doing this, depending on Several the sizes and charges of the ions . the 1 Structures of Ionic Crystals q NaCl 1 Ionic Solids CsCl CaF2 CaF Figure 7.4 1 Structure and Properties qWhy are ionic solids brittle, whereas Why metallic solids are malleable? metallic 1 Structure and Properties Brittleness 1 Strength of Ionic Bonds q Ionic bonds are very strong, so separating Ionic ions requires much energy ions q Results in unique properties: qHigh melting points, boiling points qHigh heats of fusion and vaporization qCrystals are hard and brittle qElectrical insulators when solid, electrical Electrical conductors when molten or dissolved in water conductors 1 Lattice Energy q Lattice energy is the energy required to Lattice completely separate a mole of solid ionic compound into its gaseous ions. q Proportional to ion charge q Inversely proportional to ionic radii (distance). (distance). qNaCl or NaF qNaCl or MgCl2 qMgO or MgCl2 1 Lattice Energy q Lattice energy is the energy required to Lattice completely separate a mole of solid ionic compound into its gaseous ions. q Proportional to ion charge q Inversely proportional to ionic radii (distance). (distance). qNaCl or NaF NaCl NaF qNaCl or MgCl2 NaCl MgCl qMgO or MgCl2 1 Which of these has the lowest lattice energy? 1. CaO 2. CaF2 3. CaCl2 0% 1 0% 2 0% 3 1 8.3 Covalent Bonding q Covalent bonding Covalent results from the sharing of electron density. Covalent bonding occurs in molecules between molecules nonmetals. nonmetals. 2 Single Covalent Bonds q Sharing of 1 pair of electrons q Each atom has a half-filled valence orbital Each that overlap one another that q H. + .H → H:H q Single bond represented as H:H or H-H Called a Lewis formula or electron-dot Called formula formula 2 Single bonds between like atoms q Halogens Why do Why they all have the same Lewis formula? formula? 2 Single bonds between unlik...
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