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1 Introduction to the Building Blocks of Minerals 2 What Determines the Physical Properties of a Mineral? • Chemistry • Internal structure 3 Definitions: ¢ Mineral: any naturally-occurring, solid element or compound, with a crystalline form and a defined chemistry 4 Definitions: ¢ Mineral: any naturally-occurring, solid element or compound, with a crystalline form and a defined chemistry 5 Periodic Table of Elements 6 7 8 The basic components of atoms The nucleus is minuscule compared to the volume of the atom, but contains most of the mass 9 The basic components of atoms The nucleus is made of protons and neutrons 10 The basic components of atoms wThe Electron mass = 1/1846 of a proton, charge = -1 11 Atomic number Every atom of the same element has the same number of protons in its nucleus – the atomic number Each element has a specific atomic number, which differs from the atomic number of all other elements 12 Atomic number Every atom of the same element has the same number of protons in its nucleus – the atomic number Each element has a specific atomic number, which differs from the atomic number of all other elements 13 Atomic mass (weight) 1 The number of neutrons in the nucleus can vary without causing the atom’s identity to change; the atomic mass (weight) may vary 14 15 16 Two different models of an atom Energy Levels of Electron Shells Facts about atoms outermost shell filled with electrons = STABLE CONFIGURATION 17 18 19 20 21 Periodic table of elements How are atoms bonded to form a mineral? Ionic bonding Ionic bonding Ionic bonding Ion – An electrically charged atom nWhen an atom is missing electrons = cation; has a positive charge (Na+) 22 Ionic bonding Ion – An electrically charged atom 23 nWhen an atom is missing electrons = cation; has a positive charge (Na+) nWhen an atom has too many electrons = anion; has a negative charge (Cl-) Ionic bonding 24 Halite (NaCl) – An example of ionic bonding 25 Chemical compounds - Ionic bonding The properties of a chemical compound are very different from the properties of the elements comprising it. Chlorine (Cl) gas = green, poisonous! Sodium (Na) = soft, silvery metal Cl- + Na+ = table salt! 26 27 Covalent bonding Atoms share electrons to achieve electrical neutrality 2 Covalent compounds are generally stronger than ionic bonds 28 Covalent bonding – sharing of valence electrons 29 Ionic and covalent bonds 30 wBoth ionic and covalent bonds typically occur in the same compound (mineral) wBonds are seldom 100% ionic or covalent in character Covalent bonding in diamond 31 32 Metallic bonding (not chemical bonding) Metallic bonding (not chemical bonding) Valence electrons are free to migrate among atoms The migrating electron creates a “glue” Weaker and less common than ionic or covalent bonds Ex: Cu, Au, Al as a result have high electrical conductivity 33 34 What does all this have to do with Earth materials? Minerals as Crystalline Solids The ions of a mineral are arranged in systematic, regular networks whose geometric configurations are repeated. 35 36 Crystal Lattice of Halite (NaCl) What does all this have to do with minerals? Oxygen is the most abundant element in the earth’s crust Oxygen comprises 93% of the volume of an average rock Silicon is the second most abundant element Ex: Oxygen + Silicon = Quartz 37 3