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  

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) 

STRUCTURE-CONTD

MODEL OF AN ATOM-Fig

Figure 2.5: Model of an atom.

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: 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

ATOM & COMPOUND

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

ENERGY LEVEL DIAGRAM-H ATOM

ENERGY-LEVEL DIAGRAM – He ATOM

ENERGY-LEVEL DIAGRAM – Li ATOM

ENERGY-LEVEL DIAGRAM – Na ATOM

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.

IONS

* 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 

OCTET RULE

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 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. 

METALLIC & INTERMOLE. BONDING

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 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.

MINERALS DEPEND ON

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%

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

POLYMORPHISM

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. 

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 SCALE

 MOH’S HARDNESS SCALE:

MINERAL HARDNESS TALC1 1

GYPSUM2 2

CALCITE 3

APATITE 5

QUARTZ 7

TOPAZ 8

CORUNDUM 9

DIAMOND 10

FINGER NAIL 2.5

GLASS 5-6

STEEL FILE 6.5

SCALE-CONTD.

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 

CLEAVAGE

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

SMELL & TASTE

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