Structure of atoms
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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
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


Structure contd
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)


Model of an atom fig

Figure 2.5: Model of an atom.

MODEL OF AN ATOM-Fig


Minerals
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



Atom compound
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


Energy level
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.






Structure of atoms
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
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
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



Metallic intermole 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
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


Structure of atoms

  • 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
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 )



Minerals depend on
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.





Polymorphism
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



Mineral identification
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
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



Scale contd
SCALE-CONTD.

FINGER NAIL 2.5

GLASS 5-6

STEEL FILE 6.5


Cleavage
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

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


Structure of atoms

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


Structure of atoms

  • ROCK – FORMING MINERALS:

  • FIVE GROUPS OF MINERALS

  • SILICATES ( Si, O + 1 OR 2 COMMON ELEMENTS)

  • CARBONATES (C, Ca, O)

  • OXIDES

  • SULFATES

  • SULFIDES


Structure of atoms

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)


Structure of atoms


Structure of atoms
.

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)




Structure of atoms

NAMING A MINERAL

*~ 40 NEW MINERALS/YEAR

* >3000 MINERALS KNOWN

*GEOGRAPHICAL LOCATION

* DISTINCT PHYSICAL CHARACTERISTIC

*CHEMICAL FORMULA BASED NAME WOULD NOT WORK –

POLYMORPHISM EXISTENCE


Structure of atoms

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)



Structure of atoms

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


Structure of atoms

*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