Transcript 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)
NEUTRONS --------- NEUTRAL
238
92
U MASS ------- AMU
= 238 AMU
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)
Figure 2.5: Model of an atom.
MODEL OF AN ATOM-Fig
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
PERIODIC TABLE
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 -------
232U
92 ,
14C
6
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.
ENERGY LEVEL DIAGRAM-H
ATOM
ENERGY-LEVEL DIAGRAM –
He ATOM
ENERGY-LEVEL DIAGRAM –
Li ATOM
ENERGY-LEVEL DIAGRAM –
Na ATOM
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.
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
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
IONIC BONDING
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.
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
• 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
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 )
NaCl STRUCTURE
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.
GRAPHITE STRUCTURE
DIAMOND STRUCTURE
ELEMENTAL ABUNDANCE
CRYSTAL
ABUNDANCE
ENTIRE EARTH
OXYGEN
45.20%
29.3%
IRON
5.80%
34.8%
SILICON
27.2 %
14.7%
ALUMINIUM
8.0%
1.2%
CALCIUM
5.06%
1.4%
MAGNESIUM
2.77%
11.3%
SODIUM
2.32%
<1%
POTASSIUM
1.68%
<1%
SULFUR
<1%
3.3%
NICKEL
<1%
2.4%
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
DIAMETERS OF IONS
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.
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
MOH’S HARDNESS SCALE:
MINERAL
HARDNESS
TALC1
1
GYPSUM2
2
CALCITE
3
APATITE
5
QUARTZ
7
TOPAZ
8
CORUNDUM
9
DIAMOND
10
SCALE-CONTD.
FINGER NAIL
2.5
GLASS
5-6
STEEL FILE
6.5
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
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
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
ROCK – FORMING MINERALS:
FIVE GROUPS OF MINERALS
•SILICATES ( Si, O + 1 OR 2 COMMON ELEMENTS)
•CARBONATES (C, Ca, O)
•OXIDES
•SULFATES
• SULFIDES
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)
•IN CRUST > 1000 DIFF SILICATE MINERALS
•FIVE MAJOR PRINCIPAL CRYSTAL STRUCTURE:
*INDEPENDENT TETRAHEDRA
*SINGLE CHAINS
*DOUBLE CHAINS
*SHEET
*3-D FRAMEWORK
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)
DRY CLAY MINERAL STRUC
EXPANSION DUE TO ADSOR
NAMING A MINERAL
*~ 40 NEW MINERALS/YEAR
* >3000 MINERALS KNOWN
*GEOGRAPHICAL LOCATION
* DISTINCT PHYSICAL CHARACTERISTIC
*CHEMICAL FORMULA BASED NAME WOULD NOT WORK –
POLYMORPHISM EXISTENCE
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)
Geology at a Glance (continued).
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
*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