Z = proton number = atomic number N = neutron number A = mass number (Z+N) Atomic mass of nuclide = (rest mass – binding energy) relative to 1/12 mass of 12 C atom, measured in atomic mass units – amu’s (must be looked up) Atomic weight of element = sum of the masses of the isotopes of that element times their atomic abundance (found in most textbooks)
Pauli exclusion principle Hunds rule Electrons & orbitals
Ionic bonding produces close- packed structures. There is a balance between attraction of oppositely charged ions and repulsion by outer electrons on both. Radius ratio = radius of cation/anion in a bond. This determines the coordination number
Crystal field splitting – orbitals change energy in a surrounding crystal lattice Leads to high spin (larger radius) and low spin electron configurations Produces color in minerals (example Fe +3 with 5 d electrons)
Common silicates and oxides: CN = 4 (Si, Al) CN = 6 (Mg, Fe) CN = 8 (Ca, Na) In mantle: olivine, orthopyroxene, clinopyroxene, spinel, garnet
In the earth, abundant elements form minerals with specific coordination polyhedra or sites. Minor elements either substitute or form rare minerals. The ability to substitute is controlled by:1) radius; 2) charge (valence); 3) electronegativity (bonding behavior) Contours are enrichment in crust/mantle
Mineral/melt partition or distribution coefficients Ionic radius K D = concentration in mineral concentration in liquid Eu has two valences: Eu +2 and Eu +3
You can calculate partition coefficients for any element in any mineral from the radius of the mineral site and elastic properties of the mineral.
Continental crust is complement to depleted mantle Bulk partition coefficient = sum of each mineral Kd X the abundance of the mineral during melting or crystallization Bulk Kd > 1 – element is compatible, Bulk Kd < 1 - incompatible
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