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Clerical:
Exam #2 returned - Exam #2 Grade Distribution.
Themes of the Day:
- Minerals Defined
- Basic Chemistry Review
- Chemical Bonding & Crystalline Structures
Minerals Defined
- Definition
- Occurs Naturally
- Inorganic
- Solid
- Characteristic Chemical Formula
- Crystalline Structure
- Mineral - Yes or No? Examples: coal (Kentucky's state "mineral"), cubic zirconia, pearl, mercury, glacier ice, volcanic glass, etc.
Musical Interlude: The Elements by Tom Lehrer (music by Sir Arthur Sullivan). Sing along!
Now also available in a Flash animation!!!
Basic Chemistry Review
- Minerals are built from atoms that are chemically bonded together in crystalline lattices.
- The Atom: Nucleus (Protons, Neutrons), Electrons
- Isotopes (variable numbers of neutrons) used for isotopic age dating
- Ions - charged atoms with # of electrons not equal to # of protons - important for bonding
- Anions - negative charge - # of Electrons > # of Protons - ex. Chlorine (Cl-), Oxygen (O2-)
- Cations - positive charge - # of Electrons < # of Protons - ex. Sodium (Na+), Magnesium (Mg2+)
- Periodic Table - helps predict ionic charges
- Ions with similar charges and sizes may substitute for each other in some minerals
- Abundance of elements in the Earth's crust:
| Element |
Chemical Symbol and
Common Ion(s) |
Percent
(by weight) |
| Oxygen |
O2- |
46 |
| Silicon |
Si4+ |
28 |
| Aluminum |
Al3+ |
8 |
| Iron |
Fe2+ or Fe3+ |
6 |
| Magnesium |
Mg2+ |
4 |
| Calcium |
Ca2+ |
2.4 |
| Potassium |
K1+ |
2.3 |
| Sodium |
Na1+ |
2.1 |
| All others |
|
<1 |
Chemical Bonding and Crystalline Structures
- Bonding is what happens when ions share electrons.
- Four basic types
- Ionic bonds - electron(s) completely transferred - e.g., Halite (NaCl) - tend to be brittle bonds
- Covalent bonds - electron(s) more evenly shared - e.g., Diamond (C) - strong bonds (diamond is strongest)
- Metallic bonds - transition metal nuclei swimming in a sea of shared electrons - e.g., Gold (Au) - malleable
- Intramolecular bonds - including hydrogen bonds and Van der Waals bonds - generally weak (often feels greasy) - e.g., graphite (C) or talc (Mg3AlSi3O10(OH)2)
- Silicate minerals, containing covalently bonded SiO4 tetrahedra are most common in Earth's crust and mantle
- Unit Cell - smallest building block that has all of a mineral's structural and chemical characteristics
- Crystal Systems - mineral groupings based on internal symmetry - sometimes reflected in ideal crystal shapes - e.g. quartz and ice belong to the Hexagonal crystal system, halite is cubic
- Bond types and crystaline structure are directly related to physical properties (see below) - e.g. Diamond & Graphite
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