1. Bonding in Solids In molecular solids, the particles are held to each other by IMFs. -- mol. solids are soft, w /low MPs 80 5 111 –95* 182 43 benzene CH 3 OH toluenephenol BP ( o C) MP ( o C) Why? nonpolar; weak LDFs *stronger LDFs than C 6 H 6, but doesn’t pack as closely in solid form H-bonding (strongest IMF)

2. In covalent-network solids, particles are held together in large networks by covalent bonds. -- harder – and have higher MPs – than molecular solids model of covalent- network solid -- e.g., diamond, graphite model of molecular solid In a molecular solid, the particles are held to each other by IMFs. IMFs

3. good conductor along its layers. NOTE: Graphite has layers of covalently-bonded C atoms w /delocalized,  e – s (similar to benzene). Therefore, graphite is a... The layers are held to each other by… weak LDFs. e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– + –

4. Ionic solids consist of ions held together by ionic bonds. -- MPs depend largely on magnitude of charges. -- e.g., MP of KCl = ______; MP of CaO = ______ 776 o C 2572 o C  Ionic size is a lesser factor. potassium chloride (KCl)calcium oxide (CaO)

5. Metallic solids consist entirely of metal atoms. -- these have HCP, CCP/FCC, or BCC structures, w /each atom touching 8 or 12 others -- bonding is due to delocalized valence e – that are free to move throughout solid ** responsible for metallic properties (good heat and elec. conductors, ductile/malleable, etc.) -- metallic bond strength increases w /# of v.e – e.g. MP of Li = ______; MP of Fe = ______ 181 o C1538 o C

6. C-only or Si-anything: covalent-network nonmetals only (including C-anything): molecular metals only: metallic metal-nonmetal: ionic

7. Metallic Properties -- heat and elec. conductivity… v.e – are free to move throughout material. -- Via the v.e –, atoms w /high thermal energy can pass it on to others w /less. -- Since the v.e – are charged (i.e., negatively), a  V causes them to migrate as a group. e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– A spool of copper wire. Cu is an excellent conductor, second only to Ag (and followed by Au and then Al).

8. Metallic Properties, cont. -- ductility/malleability… e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– e–e– (Some are pushed closer together, some are stretched farther apart). The mobile v.e – move to counteract those stresses. Because v.e – in ionic and covalent solids aren’t mobile, these substances are insulators and are generally brittle. When a metal is bent, the nuclei and core e – are forced into a nonuniform arrangement.