1. Chemical Bonds Electrical in nature- responsible for most mineral properties 1) Ionic Na: low 1st IP  e -  Na + (Ne config) Cl: high e-neg takes e- & = Cl - (Ar config) Now they have opposite charges & attract  bond Poor electrical conductors. Bonding is strong (high melting point) disrupted by polarized solvents (water) Bonding is non-directional, symmetry of atomic arrangement is high

2. Chemical Bonds 2) Covalent Sharing electrons such as in Si-O, S-O, P-O, C-O and C-C Double bonds when 2 orbitals shared, e.g. V=O, U=O, C=O Triple bonds when 3 orbitals shared; e.g. N=N

3. Chemical Bonds Hybrid orbitals Carbon:  |  |     |     1s 2s 2p 1s 2(sp 3 ) C-C-C angle = 109 o 28’ Fig 8-8 of Bloss, Crystallography and Crystal Chemistry. © MSA

4. Chemical Bonds Hybrid orbitals Alternatively: Carbon:  |  |     |    |  1s 2s 2p 1s 2(sp 2 ) 2p The 3 2(sp 2 ) orbitals are coplanar & 120 o apart

5. Chemical Bonds Fig 8-8 of Bloss, Crystallography and Crystal Chemistry. © MSA Graphite structure

6. Covalent structures diamond 4 x 2(sp) 3 Hybrids Graphite 3 x 2(sp 2 ) Hybrids Chemical properties of minerals containing only one type of bonds listed in Table 3.9 of text book

7. 3) Metallic Bonding Atoms are closely packed in metal structures. "touching" nearest neighbors A high density of valence e - around any given atom & also a high density of neighbor atoms around the loose valence e - The effect is to show such a general attraction for these e - that they become free to maintain an electrical neutrality: Electron gas = good conductivity Further good ductility Chemical Bonds

8. 4) Van der Waals Bonds Weakest bond Usually between neutral molecules (even large ones like graphite sheets) Produced by polar or partial polar covalent bonds or polar atoms Weakness of the bond is apparent in graphite cleavage Condensed Cl 2 cov VdW

9. Hydrogen bonds Stronger bond that VAN DER WAALS bond Occurs between polar groups of atoms in liquids and solids e.g. H 2 O - + - - - - - - + ++ + + +

10. Water and Ice