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Lecture 3. Orders of magnitude From planets to atoms

Lecture 3. Orders of magnitude From planets to atoms. Example of coordination number. SiO 2 CN Si = 4. Atomic and ionic radii In picometers (pm). How big is an atom? ~100 picometers (pm) or ~1 Angstrom. Lengthscales in nature span more than 27 orders of magnitude.

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Lecture 3. Orders of magnitude From planets to atoms

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  1. Lecture 3. Orders of magnitude From planets to atoms

  2. Example of coordination number SiO2 CNSi = 4

  3. Atomic and ionic radii In picometers (pm)

  4. How big is an atom? ~100 picometers (pm) or ~1 Angstrom

  5. Lengthscales in nature span more than 27 orders of magnitude Diameter of Milky Way Galaxy 100 kilo-lightyears Distance to Neptune from Earth 4.3 x 109 km Radius of Sun 7 x 105 km Radius of Earth 6.37 x 103 km Thickness of Earth’s continental crust 3.2 x 101 km Depth of oceans 4 km Deepest hole drilled into the Earth 10 km Tallest building on Earth 1.3 km Length of a soccer field 109.7 m Diameter of soccer ball 0.22 m Dimensions of soccer goal 2.44 by 7.135 m Size of an ant 1 mm Size of an atom 0.1 nm 1 lightyear = 9.46 x 1015 m

  6. Orders of magnitude 1,250,000 is 1.25 x 106 or 1.25 billion Numbers can be converted to scientific notation The base 10 logarithm (or log10) gives you the order of magnitude of that number For example… log10(1,250,000) = log10(1.25 x 106) = log10(1.25) + log10(106) = log10(1.25) + 6 Since log10(1) = 0, we say that 1,250,000 is on the order of 1 million (106)

  7. Metric system units [LENGTH] km m cm mm μm nm pm kg g mg μg ng pg =103 m =100 m =10-2 m =10-3 m =10-6 m =10-9 m =10-12 m =103 g =100 g =10-3 g =10-6 g =10-9 g =10-12 g [MASS] Do not confuse metric units with miles, inches, or pounds.

  8. Rough diamonds Kimberly diamond mine in S Africa Diamond mine NWT, Canada

  9. Gypsum CaSO4(H2O)2 Gypsum crystals from a Lead mine in Mexico

  10. Z = Proton Number N = number of neutrons A = Atomic Mass Number = Z + N An element is defined by its proton number Number of protons and electrons dictates chemical behavior of atom

  11. Electronegativity Tendency for an atom to attract an electron in a molecule

  12. Chemical bonding Similar electronegativity Contrasting electronegativity Covalent bonds tend to be stronger than ionic bonds

  13. Al 1.41 Ca 1.54 ? 2.9 Ni 1.8 Fe 32.1 O 30.1 Si 15.1 Mg 13.9 BULK EARTH

  14. Majority of earth materials are made up of silicates Silicates are mineral compounds that have silica tetrahedra as their basic building blocks, e.gSiO4-4 Si-O bond is dominantly covalent

  15. Quartz SiO2 Silica tetrahedra are linked at all apices Fully polymerized One of the most common minerals in the continents

  16. [SiO4]4- Independent tetrahedraNesosilicates Olivine Mg2SiO4 (aka peridot) Abundant mantle mineral Garnet (Mg,Ca,Fe)3Al2Si3O12 Common crustal mineral

  17. Nesosilicates: independent SiO4tetrahedra OLIVINE SiO4tetrahedra are not linked to each other -separated by Mg2+cations that are ionically bonded to O2- apices of the silica tetrahedra Olivine (100) view blue = M1 yellow = M2 http://www.whitman.edu/geology/winter/

  18. Peridotite An olivine-rich rock that makes up much of the mantle

  19. n[SiO3]2-n = 3, 4, 6 Cyclosilicates Examples: benitoiteBaTi[Si3O9] axiniteCa3Al2BO3[Si4O12]OH beryl Be3Al2[Si6O18] tourmaline CaMg3Al6(BO3)3(Si6O18(OH)4 Beryl with charge transfer = aquamarine Beryl with Cr = Emerald tourmaline http://www.whitman.edu/geology/winter/

  20. PYROXENES Spodumene (kunzite) LiSiO3 [SiO3]2- single chains pyroxenes pyroxenoids Dark green mineral in peridotite Diopside CaMgSi2O6 Common mineral in the mantle

  21. Amphiboles Hornblende (Ca,Na)2–3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2 [ [Si4O11]4- Double tetrahedra amphiboles One of the common “black” minerals in granitoids

  22. Phyllosilicates Micas and clays [Si2O5]2- Sheets of tetrahedra Phyllosilicates micas talc clay minerals serpentine http://www.whitman.edu/geology/winter/

  23. Biotite K(Mg,Fe)3(AlSi3O10)(F,OH)2 Common “black” mineral in granitoids Differs from hornblende in being flaky and sheet-like

  24. Tectosilicates Feldspars and quartz low-quartz [SiO2] 3-D frameworks of tetrahedra: fully polymerized Tectosilicates quartz and the silica minerals feldspars feldspathoids zeolites http://www.whitman.edu/geology/winter/

  25. FELDSPARS Plagioclase CaAlSSi2O8 Orthoclase (K,Na)AlSi3O8 Common minerals in granitic rocks The precursor of clays used in ceramics

  26. What did we learn today • Concepts of orders of magnitude • Chemical Bonding • Basic minerals on Earth Next lecture – physical properties of rocks and minerals

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