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STRUCTURE OF ATOMS

STRUCTURE OF ATOMS. DIAMETER ~ 10 -8 CM (0.00000001CM) ATOMS CONSISTS OF OUTER ELECTRONS NUCLEUS – COMPOSED OF PROTONS AND NEUTRONS CHARGE OF A PROTON = +1---------1.60*10 -19 C MASS OF A PROTON = 1.67*10 -24 G =1 ATOMIC MASS UNIT (AMU)

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STRUCTURE OF ATOMS

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  1. STRUCTURE OF ATOMS DIAMETER ~ 10-8 CM (0.00000001CM) ATOMS CONSISTS OF OUTER ELECTRONS NUCLEUS – COMPOSED OF PROTONS AND NEUTRONS CHARGE OF A PROTON = +1---------1.60*10-19 C MASS OF A PROTON = 1.67*10-24 G =1 ATOMIC MASS UNIT (AMU) NEUTRONS --------- NEUTRAL 23892 U MASS ------- AMU = 238 AMU

  2. STRUCTURE-CONTD ELECTRONS TRAVEL AROUND THE NUCLEUS ME =MP/1836 ------- MP= ME * 1836 NUMBER OF PROTONS (Z) = ATOMIC NUMBER NUMBER OF ELECTRONS = NUMBER OF PROTONS ISOTOPES : ATOMS OF SAME ELEMENT WITH DIFFERENT NEUTRON NUMBER ( SAME Z BUT DIFFERENT ATOMIC WEIGHT)

  3. Figure 2.5: Model of an atom. MODEL OF AN ATOM-Fig

  4. MINERALS MINERALS: NATURALLY OCCURRING SOLIDS WITH SPECIFIC CHEMICAL COMPOSITIONS AND DEFINITE INTERNAL STRUCTURES e.g., QUARTZ, EMRALDS, ETC ROCKS: NATURALLY OCCURRING AGGREGATES OF ONE OR MORE ELEMENTS ELEMENTS: FORM OF MATTER THAT CANMNOT BE BROKEN DOWN INTO SIMPLER FORM BY HEAT, COLD OR REACTION WITH OTHER ELEMENTS 112 ELEMENTS 92 NATURAL 20 LAB CREATION

  5. PERIODIC TABLE

  6. ATOM & COMPOUND ATOM: SMALLEST PARTICLE OF AN ELEMENT * ATOMS OF AN ELEMENT ARE ESSENTIALLY IDENTICAL * ATOMS OF ONE ELEMENT DIFFER FROM ATOMS OF EVERY OTHER ELEMENT COMPOUNDS: ONE OR MORE ELEMENTS COMBINE IN SPECIFIC PROPORTIONS TO FORM CHEMICAL COMPOUNDS EX: QUARTZ Si O2 (ONE Si ATOM 2 OXYGEN ATOMS) 18 O, 17 O, 16 O = ISOTOPES OF OXYGEN ( STABLE ISOTOPES) RADIOACTIVE ISOTOPES ------- 232U92 , 14C6

  7. ENERGY LEVEL ENERGY LEVEL: SPECIFIC REGION OF SPACE AROUND THE NUCLEUS WHERE AN ELECTRON MOVES. ELECTRONS FILL THE LOWEST ENERGY LEVELS BEFORE THEY START FILLING HIGHER LEVELS --- LOWEST ENERGY LEVEL 2 ELECTRONS --- NEXT ENERGY LEVEL 8ELECTRONS --- NEXT ENERGY LEVEL 8 ELECTRONS --- NEXT ENERGY LEVEL 18ELECTRONS BONDING: ATOMS COMBINE TO FORM CHEMICAL COMPOUNDS IN A VARIETY OF WAYS KNOWN AS BONDING.

  8. ENERGY LEVEL DIAGRAM-H ATOM

  9. ENERGY-LEVEL DIAGRAM – He ATOM

  10. ENERGY-LEVEL DIAGRAM – Li ATOM

  11. ENERGY-LEVEL DIAGRAM – Na ATOM

  12. IONS IONS: ELECTRICALLY CHARGED PARTICLE * IONIC BONDING *METALLIC BONDING *COVALENT BONDING *INTERMOLECULAR BONDING TWO FACTORS THAT DETERMINE WHICH ATOMS WILL UNITE WITH OTHERS: 1.EACH ATOM SHOULD ACHIEVE CHEMICAL STABILITY 2.RESULTING COMPOUND SHOULD BE NEUTRAL.

  13. OCTET RULE * WHEN OUTER-MOST ENERGY LEVEL IS FILLED, CHEMICAL STABILITY IS ATTAINED * OCTET RULE: 8 ELECTRONS IN THE OUTERMOST ENERGY LEVEL. * ATOMS BIND WITH OTHER ATOMS BY LOSING, GAINING OR SHARING OUTER ELECTRONS -------- ATOMS WITH 1 OR 2 ELECTRONS, TEND TO GIVE UP -------- ATOMS WITH 6 OR 7 ELECTRONS, TEND TO ACCEPT -------- ATOMS WITH 3 OR 4 OR 5 ELECTRONS, TEND TO SHARE * INERT GAS

  14. IONIC AND COVALENT BONDING  ION  STRONG TENDENCY TO LOSE ELECTRONS/ STRONG TENDENCY TO GAIN ELECTRONS  IONIC BONDING COVALENT BONDING: *SHARING OF ELECTRONS *ATOMS WITH 3, 4, OR 5 ELECTRONS SHARE WITH OTHER SIMILARLY EQUIPPED ATOMS *COVALENT BONDS ARE GENERALLY STRONGER THAN ANY OTHER BOND

  15. IONIC BONDING

  16. METALLIC & INTERMOLE. BONDING METALLIC BONDING: ATTRACTION OF NEGATIVELY CHARGED ELECTRON CLOUD TO A CLUSTER OF POSITIVELY CHARGED NUCLEI. INTERMOLECULAR BONDING: WEAK BONDING BETWEEN MOLECULES – DUE TO UNEVEN DISTRIBUTION OF ELECTRONS.

  17. HYDROGEN BOND: • POSITIVE CHARGE OF OXYGEN ATOM > HYDROGEN ATOM • --- SHARED ELECTRONS ARE MORE ATTRACTED TO THE OXYGEN NUCLEUS ---- • OXYGEN SIDE DEVELOPS A WEAK NEGATIVE CHARGE – A WEAK POSITIVE • CHARGE IN H SIDE • WEAKLY CHARGED REGIONS ATTRACT OPPOSITELY CHARGED REGIONS OF NEARBY MOLECULES – HYDROGEN BONDS • H2O + NaCl ----------> Na+ + Cl- • MANY MINERALS HAVE SAME QUALITIES AS MOLECULES • MINERALS MAY BE SUBJECT TO INTERMOLECULAR BONDS • WEAK INTERMOLECULAR ATTRACTION – VAN DER WAALS BOND

  18. Summary on Bonding • Ionic bonding • Involves transfer of valence electrons from one atom to another • Covalent bonding • Involves sharing of valence electrons among adjacent atoms • Metallic bonding • Electrons flow freely throughout metals; results in high electrical conductivity

  19. MINERAL STRUCTURE: • CRYSTALS ---- A REGULAR GEOMETRIC SHAPE • CRYSTAL STRUCTURE ---- ORDERLY ARRANGEMENT OF IONS OR ATOMS INTO A LATTICE WORK OF REPEATED THREE – DIMENSIONAL UNITS • GLASS IS NOT A MINERAL – SUDDEN COOLING OF MOLTEN ROCK RESULTS IN LACK OF ORDERLY ARRANGEMENT • MINERALOIDS: CONSTANT COMPOSITION BUT, NO SPECIFIC CRYSTAL STRUCTURE EX: OBSIDIAN ( A NATURAL GLASS )

  20. NaCl STRUCTURE

  21. MINERALS DEPEND ON MINERALS AT ANY TIME & SPACE DEPENDS ON: *ELEMENTS AVAILABLE TO BOND *CHARGES AND SIZES OF IONS *TEMPERATURE AND PRESSURE AT WHICH MINERALS FORM ------ IONS & ATOMS OF SIMILAR SIZE & CHARGE ARE ABLE TO REPLACE ONE ANOTHER WITHIN A CRYSTAL STRUCTURE --- IONIC SUBSTITUTION EX: Sr IN CaCO3 MINERAL Ba, Sr IN FORAM, INORGANIC CARBONATE.

  22. GRAPHITE STRUCTURE

  23. DIAMOND STRUCTURE

  24. ELEMENTAL ABUNDANCE

  25. POLYMORPHISM IONIC SUBSTITUTION: CERTAIN IONS OF SIMILAR SIZE AND CHARGE REPLACE ONE ANOTHER WITHIN A CRYSTAL STRUCTURE, DEPENDING ON WHICH IS MOST AVAILABLE DURING THE MINERAL’S FORMATION EX: Sr 2+ IN CaCO3 (RAPLACING Ca ++) Fe 2+ AND Mg 2+ IN OLIVINE ( Fe, Mg )2 SiO4 POLYMORPHISM: SAME CHEMICAL COMPOSITION BUT DIFFERENT PHYSICAL STRUCTURE ( DIFF PHYSICAL PROPERTIES) POLY: MANY MORPH: FORMS OR STRUCTURES EX: GRAPHITE AND DIAMOND ARAGONITE AND CALCITE

  26. DIAMETERS OF IONS

  27. MINERAL IDENTIFICATION: • FIELD • LABORATORY COLOR: LEAST RELIABLE IDENTIFYING CHARACTERISTIC LUSTER: DESCRIBES HOW A MINERAL’S SURFACE REFLECTS LIGHT ( VIBRATING ELECTRONS EMIT A DIFFUSE LIGHT, GIVING METALLIC SURFACES THEIR CHARACTERISTIC SHINY LUSTER) STREAK: COLOR OF A MINERAL IN ITS POWDERED FORM – OFTEN A MORE ACCURATE INDICATOR OF MINERAL IDENTITY.

  28. MOH’S SCALE HARDNESS: MINERAL’S RESISTANCE TO SCRATCHING OR ABRASION – MINERAL’S HARDNESS INDICATES THE RELATIVE STRENGTH OF ITS BONDS MOH’S HARDNESS SCALE: ASSIGNS RELATIVE HARDNESSES TO SEVERAL COMMON AND A FEW RARE AND PRECIOUS MINERALS

  29. MOH’S HARDNESS SCALE:

  30. SCALE-CONTD. FINGER NAIL 2.5 GLASS 5-6 STEEL FILE 6.5

  31. CLEAVAGE CLEAVAGE: TENDENCY OF A MINERAL TO BREAK CONSISTENTLY ALONG DISTINCT PLANES IN THEIR CRYSTAL STRUCTURES WHERE THE BONDS ARE WEAKEST, OR FEWER IN NUMBER TWO MINERALS THAT ARE SIMILAR IN EXTERNAL FORM, HARDNESS AND OTHER CHARACTERISTICS MAY HAVE DIFFERENT CLEAVAGE PLANES FRACTURE: WHEN BONDS ARE EQUALLY STRONG IN ALL DIRECTIONS AND DISTRIBUTED UNIFORMLY MINERALS DO NOT CLEAVE – THEY FRACTURE AT RANDOM EXAMPLE: QUARTZ – ALL ATOMS BOND COVALENTLY

  32. SMELL & TASTE SMELL & TASTE: HALITE SALTY KCl BITTER SULFUR CONTAINING MINERALS – H2S SMELL EFFERVESCENCE: CaCO3 + HCl ---------> EFFERVESCENCE NaCl + HCl ---------> NO EFFERVESCENCE CRYSTAL FORM: SHAPE OF A WELL FORMED CRYSTAL MAY BE DISTINCTIVE ENOUGH TO IDENTIFY THE MINERAL

  33. LABORATORY SPECIFIC GRAVITY=SUBSTANCE WEIGHT /WEIGHT OF EQUAL VOLUME OF H2O DENSITY = MASS (G) / VOLUME (CM3) POLYMORPHS HAVE SLIGHTLY DIFFERENT DENSITIES EX: GRAPHITE 2.3 DIAMOND 3.5 (COMPRESSED CRYSTAL STRUCTURE) OTHER LAB TESTS: BY TRANSMITTED LIGHT THROUGH A THIN SECTION UNDER UV CERTAIN MINERALS GLOW –FLUORESCENCE PHOSPHORESCENCE – GLOW AFTER UV LIGHT IS REMOVED

  34. ROCK – FORMING MINERALS: • FIVE GROUPS OF MINERALS • SILICATES ( Si, O + 1 OR 2 COMMON ELEMENTS) • CARBONATES (C, Ca, O) • OXIDES • SULFATES • SULFIDES

  35. Silicate Structures • The Silicon-Oxygen tetrahedron • Strongly bonded silicate ion • Basic structure for silicate minerals • Sharing of O atoms in tetrahedra • The more shared O atoms per tetrahedron, the more complex the silicate structure • Isolated tetrahedra (none shared) • Chain silicates (2 shared) • Double-chain silicates (alternating 2 and 3 shared) • Sheet silicates (3 shared) • Framework silicates (4 shared)

  36. IN CRUST > 1000 DIFF SILICATE MINERALS • FIVE MAJOR PRINCIPAL CRYSTAL STRUCTURE: • *INDEPENDENT TETRAHEDRA • *SINGLE CHAINS • *DOUBLE CHAINS • *SHEET • *3-D FRAMEWORK

  37. . Non-silicate Minerals • Carbonates • Contain CO3 in their structures (e.g., calcite - CaCO3) • Sulfates • Contain SO4 in their structures (e.g., gypsum - CaSO4.2H2O) • Sulfides • Contain S (but no O) in their structures (e.g., pyrite - FeS2) • Oxides • Contain O, but not bonded to Si, C or S (e.g., hematite - Fe2O3) • Native elements • Composed entirely of one element (e.g., diamond - C; gold - Au)

  38. DRY CLAY MINERAL STRUC

  39. EXPANSION DUE TO ADSOR

  40. NAMING A MINERAL *~ 40 NEW MINERALS/YEAR * >3000 MINERALS KNOWN *GEOGRAPHICAL LOCATION * DISTINCT PHYSICAL CHARACTERISTIC *CHEMICAL FORMULA BASED NAME WOULD NOT WORK – POLYMORPHISM EXISTENCE

  41. Minerals • A mineral must meet the following criteria: • Crystalline solid • Atoms are arranged in a consistent and orderly geometric pattern • Forms through natural geological processes • Has a specific chemical composition • Rock-forming minerals • Although over 4000 minerals have been identified, only a few hundred are common enough to be generally important to geology (rock-forming minerals) • Over 90% of Earth’s crust is composed of minerals from only 5 groups (feldspars, pyroxenes, amphiboles, micas, quartz)

  42. Geology at a Glance (continued).

  43. CHAPTER-2 SUMMARY *DEFINITION OF A MINERAL, ROCK *DEFINITION OF MINERALOIDS *OPAL, GLASS *ATOMIC MASS, ATOMIC WEIGHT, ISOTOPE *WHAT DETERMINES WHETHER AN ATOM WILL BIND ANOTHER ATOM *IONIC BOND *COVALENT BOND *METALLIC BOND *HYDROGEN BOND

  44. *VAN DER WALLS BOND *POLYMORPHISM *BEST SINGLE PROPERTY TO IDENTIFY MINERALS *OTHR MINERAL IDENTIFICATION TECHNIQUES *MINERAL HARDNESS *SPECIFIC GRAVITY *MOST ABUNDANT MINERAL GROUP *QUARTZ – CONSTITUENTS & STRUCTURE *NAMING OF MINERALS

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