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Atoms are the smallest components of nature
with the properties of a given substance. Electrons (negative charge) Protons (positive charge) Neutrons (no charge) Suggested tips to give students: Protons are “positive”. Neutrons are “neutral”.
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For any given element: Atomic Number is the number of protons in the nucleus. Mass Number is the number of neutrons and protons in nucleus. Suggested tips to give students: What is the Atomic Number of carbon? (6) What is the Mass Number of carbon? (12)
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Variations in mass number create Isotopes
Suggested tips to give students: Iso (equal) tope (place) = same place in Periodic Table of The Elements. Variations in mass number create Isotopes
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Atoms bond to achieve a stable electron configuration
Atoms bond to achieve a stable electron configuration. Most atoms bond to achieve 8 electrons in the outer shell - the so-called “Octet Rule”
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Variations in electrical charge form Ions negative charge = Anion
positive charge = Cation
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Minerals are compounds of atoms bonded together
… “to achieve a stable electron configuration” … IONIC BONDING Suggested tips to give students: “Opposites attract”
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COVALENT BONDING METALLIC BONDING
… “to achieve a stable electron configuration” … Suggested tips to give students: “sharing” METALLIC BONDING Bonding between atoms within metals. All “free” electrons shared in an “electron sea”.
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Igneous Minerals crystallize from cooling magma.
Sedimentary Minerals crystallize from dissolved elements in water, or as a product of biological metabolism. Suggested tips to give students: Whole chapters devoted to each type coming up! Metamorphic Minerals recrystallize from existing minerals where conditions in the crust cause high heat and pressure.
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Magma from three major tectonic settings
Suggested tips to give students: Where Igneous Minerals are formed - source rock.
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Oxygen and Silicon are the two most abundant elements in the crust.
Suggested tips to give students: Oxygen and silicon content is high in minerals that crystallize from melted crustal rock. Minerals that come from the mantle are high in iron.
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Silica - 4 oxygen atoms surround a single silicon atom, forming (SiO4)4- Each oxygen atom covalently shares 1 electron with the silicon atom, jointly filling its outermost shell. O2- 2e 8P 6e Suggested tips to give students: Atoms in a liquid, either magma or water, arrange in an orderly fashion (due to electrical charges), progressively building crystals. Silica tetrahedron on left. Halite example on right. Si4+ 8e 2e 4e 14P
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Types of Silicate Structures
Na+ Ca 2+ Al 3+ Fe 2+ (3+) Mg 2+ K + Suggested tips to give students: Whatever the ultimate crystal structure, by the time a mineral has completed crystallization, it is electrically neutral. Silicate structures are not neutral – still require cations. Metallic Cations
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Metallic Cations Join Silicate Structures to Form Neutral Compounds.
Cations of like size and charge substitute within silicate structures. This forms a wide variety of minerals. Most substituted Cation pairs are Na+/Ca2+, Al3+ /Si4+, and Fe2+/Mg2+. Olivine forms by Single Cation Substitution. Plagioclase Feldspar forms by Double Cation Substitution. (Mg2+, Fe2+)2Si4+O2-4
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Mg2+ Fe2+ Single Substitution Ca2+ Na+ Double Substitution Si4+ Al3+
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Olivine: single tetrahedron (SiO4)4-
[Fe22+(Si4+O42-)4-] or [Mg22+(Si4+O42-)4-] –8 = 0 or –8=0 Fayalite (Fe2SiO4) Forsterite (Mg2SiO4) Feldspar: 3-D framework (Si3O8)4- [Na1+Al3+Si34+O82-]or [Ca2+Al23+Si24+O82-] –16=0 or –16=0 Albite NaAlSi3O8 Anorthite CaAl2Si2O8
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There are seven common rock-forming minerals.
Amphibole Olivine Pyroxene Quartz Suggested tips to give students: Group names are given to minerals with compositional variation within a particular range. Each mineral within a group has a specific composition. Common irregularities in crystallization or chemical impurities produce the variations. The Feldspar Group Orthoclase and Plagioclase Biotite Calcite
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As the Si and O build crystalline structures and the metallic cations play single and double substitution, the entire magma chamber grows into a solid mass of minerals….
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