1. Bonding Atoms come together in one of 3 principle types of bond
Ionic = + and - ions (charged atoms) joined by an electrostatic interaction
Covalent = Sharing of electrons equally between ions
Metallic – sharing of electrons between many atoms O2
Diagrams show electron density and highest energy bonding M.O.’s for each
Discuss difference between the 2
NaCl

2. Ionic vs. Covalent
Elements on the right and top of the periodic table draw electrons strongly
Bonds between atoms from opposite ends more ionic, diatomics are 100% covalent
Bond strength  Covalent>Ionic>metallic
Affects hardness, melting T, solubility
Bond type affects geometry of how ions are arranged
More ionic vs. covalent = higher symmetry
Go over this on a periodic table – this is electronegativity argument essentially
Test them a little – SiO2, CaO, AsS (realgar), ZnS (sphalerite) more or less ionic – properties?
More ionic  less strength  melts lower, more soluble
Realgar much softer than Sphalerite

3. Metallic Bonds
Electron sharing can go in any direction – results in more malleable material
Also affects electronic properties – metallic materials conduct electricity better
Affects redox reactions – where there is a transfer of electrons as a part of dissolution
electrons are nonbonding or delocalized, which makes materials less polar – and thus less soluble is water
Metallic bonding – deloalized e- (nonbonding)  electrical properties
S8 case for Van der Waals bonds --. Very weak  talc?
Good demonstration is to watch how water beads up on pyrite
Talk about how ore minerals are generally more covalent – and quite insoluble – S2- vs. SO42- bonding with metals changes this because of the ## of electrons in an ion. Bit of a curveball here – they have to think about why e- are drawn more or less strongly 

4. Bond Character Get Table 1.3 and Figure 1.11 in here
Discuss mixed character – how does this relate to M.O. theory? – All about how electrons are shared between atoms! Look at some of the examples

5. Other types of bonding
Van der Waals – Interaction between molecular units which assemble a mineral from weak electrostatic interactions
Hydrogen – H+ bonds molecular subunits together
Dative – special type of covalent bond – all bonding electrons donated by one ion
Elemental sulfur discussion – mineral with both electrostatic and covalent forces!!
Put in scanned picture of S8 structure!
Point out that ignoring Van der Waals forces is NOT what mineralogists should do! Have to ignore major classes of minerals on the surface!! Book actually says this!!
Clays – brucite for instance has sheets held together by the force hydrogen AND van der Waals bonds!! - bring in clay/ mica and demonstrate this!!!
S8 – soft, very insoluble, poor conductor

6. Ionic bonding
Most common minerals on earth are composed of ionic bonds
Covalently bonded anionic subunits are often ionically bonded to cations to form these minerals – SiO44-, CO32-, PO43-, SO42-
Mineral properties are more often compared by the anionic component, thus most classification schemes focus on this.

7. Ionic vs. Covalent Bond strength  Covalent>Ionic>metallic
Affects hardness, melting T, solubility
Bond type affects geometry of how ions are arranged
More ionic vs. covalent = higher symmetry
Go over this on a periodic table – this is electronegativity argument essentially
Test them a little – SiO2, CaO, AsS (realgar), ZnS (sphalerite) more or less ionic – properties?
More ionic  less strength  melts lower, more soluble
Realgar much softer than Sphalerite

8. Ionic bonding
Most common minerals on earth are composed of ionic bonds
Covalently bonded anionic subunits are often ionically bonded to cations to form these minerals – SiO44-, CO32-, PO43-, SO42-
Mineral properties are more often compared by the anionic component, thus most classification schemes focus on this.

9. Nesosilicates
– SiO44-
Inosilicates
(double)
– Si4O116-
Sorosilicates
– Si2O76-
Phyllosilicates
– Si2O52-
Cyclosilicates
– Si6O1812-
Inosilicates
(single)
– Si2O64-
Tectosilicates
– SiO20