Bonding in Solids

1. OH CH3 benzene toluene phenol MP (oC) 5 –95* 43 80 111 182 BP (oC) Why? Bonding in Solids In molecular solids, the particles are held to each other by IMFs. mol. solids are soft, w/low MPs -- *stronger LDFs than C6H6, but doesn’t pack as closely in solid form nonpolar; weak LDFs H-bonding (strongest IMF)

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

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

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

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– 181oC 1538oC e.g. MP of Li = ______; MP of Fe = ______

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

7. 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). e– e– e– e– e– e– e– 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 DV causes them to migrate as a group.

8. e– e– e– e– e– e– e– e– e– e– e– When a metal is bent, the nuclei and core e– are forced into a nonuniform arrangement. 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– Metallic Properties, cont. -- ductility/malleability… (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.