Basic Atomic Theory the Periodic Table

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Basic Atomic Theory the Periodic Table

• Order in the Court!

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Atomic Theory
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Atomic Theory

• Atoms smallest particles of a substance with the
  same chemical/physical properties as that
  substance.
• Protons gt stable, () charge.
• Electronsgt mobile, (-) charge.
• Neutronsgt stable, no charge.
• Nucleus of atom contains neutrons and protons.
• Electrons orbit the nucleus.
• In an electrically neutral atom, the number of
  electrons the number of protons.

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Atomic Theory

• Atomic number
• The number of protons in the nucleus determines
  the atomic number
• Change the number of protons and you change the
  element (also atomic number, atomic mass)
• Neutral atomsgt protons electrons

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Atomic Theory

• Ionsgt protons not equal to the electrons
• Cation gt protons gt electrons () Charge Ca2
• Anion gt protons lt electrons (-) Charge S-2
• Complex ion gt cation or anion group (more than 1
  element) SiO4-4, CO3-2
• See anionic complexes, (more later)
• Valence gt ionic charge (preferred ion
  configuration)
• of protons (minus) of electrons

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Atomic Theory

• Isotope
• A form of an element with a different number of
  neutrons
• Some are stable (dont spontaneously degenerate)
• Some are unstable or radioactive (spontaneously
  degenerate by nuclear reactions to form different
  elements)

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The Periodic Table, Valence, Atomic/Ionic Radius,
Bonding, and Coordination

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The Periodic Table of Elements(Order in the
Court!)

• Elemental symbols (1-2 letters) Ca, Si, etc
• Atomic
• Number of protons (or electrons) in an uncharged
  atom
• Horizontal rows are periods
• Vertical columns are groups

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The Periodic Table of Elements(Order in the
Court!)

• Chemical variation in periods (rows)
• Increasing of electrons in outer electron shell
  to capacity (8)
• Stable (chemically non-reactive) noble gases
  electron configuration (NGEC, rule of eight or
  octet rule)
• Electrons fill lowest energy (inner most)
  electron shells first (except for transition
  metals A 21-31)
• Outer most electrons are mobile and result in
  chemical reactivity the valence electrons

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The Periodic Table of Elements(Order in the
Court!)

• Chemical properties of groups (columns)
• Similar physical and chemical properties due to
  similar outer electron shell configuration
• Similar tendency to gain (group 5A-7A, and become
  (-) anions) or loose (group 1A-4A, and become ()
  cations) electrons to form ions with NGEC

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The Periodic Table of Elements(Order in the
Court!)

• Chemical properties of groups
• Group 1Agt alkali metals (electropositive)
• Valence of 1
• Group 2Agt alkaline earth metals
  (electropositive)
• Valence of 2
• Groups 1B-7B and 8gt transition metals
• More complex chemical properties
• Several valences, i.e. Fe2 (ferrous iron) and
  Fe3 (ferric iron)
• Group 3Agt metalloids (electropositive)
• Valence of 3
• Group 4Agt silica-carbon group (important mineral
  and organic compounds electropositive)
• Valence of 4

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The Periodic Table of Elements(Order in the
Court!)

• Chemical properties of groups (cont)
• Group 5Agt nitrogen-phosphorous group
  (electropositive)
• Valence of 5
• Group 6Agt oxygen group (non-metals,
  electronegative)
• Valence of -2
• Group 7Agt halogen group (non-metals,
  electronegative)
• Valence of 1
• Group 8A?Noble (inert, non-reactive ) Gases

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Valence

• Characteristic loss or gain of electrons from a
  neutral atom with an electric charge on resulting
  ion

Dark shade are the most common elements in the
crust. Make them your friends! Lighter shade
are other important elements in earth materials.
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Oxidation and Reduction

• Oxidation
• Process of loosing an electron
• Fe2 ? Fe 3
• Reduction
• Process of gaining an electron(s)
• O2? 2O-2

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Bonding in Minerals

• Most atoms are unstable because they have
  unfilled outer electron shells (rule of eight or
  octet rule)
• Exception Noble (inert) gases
• Most elements ionize gain or loose electrons and
  become charged

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Bonding

• Electrostatic force of attraction that holds
  cations, anions, and/or complex ions together in
  chemical compounds and especially, in the rigid
  geometric structures of minerals
• Opposite electric charges attract
• Like electric charges repel

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Bonding

• Electrically neutral chemical compounds (such as
  minerals) are stoichiometric (equal positive and
  negative charge?uncharged)
• Stoichiometry determines the relative proportions
  of elements in stable mineral compounds
  determined by valence of the elements involved,
  e.g.
• Fe(3)2O(-2)3
• Iron oxide (rust) hematite

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Bonding

• Ions combine to attain stoichiometry (electrical
  neutrality) and noble gas (full outer electron
  shell) electron configuration
• Particular mineral species form in order to
  minimize internal (molecular scale chemical)
  energy in accordance with external conditions of
• oT (temperature),
• P (pressure), and
• Chemical environment (composition of available
  constituents or raw materials)

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Bond Types

• Ionic bond
• Covalent bond
• Metallic bond
• Hydrogen bond
• Van der Waals bond

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Bond Types

• Bond types are not mutually exclusive within any
  mineral compound

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Bond Types

• Ionic bond
• Fundamental (dominant) bond type in 90 of all
  minerals
• Consideration of ionic bonding explains most
  mineral properties
• Electron exchange between cations and anions
  ions are surrounded by oppositely charged ions to
  satisfy the octet rule

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Bond Types

• Ionic bond
• Structure of ionic compounds determined by ionic
  radius and valence of constituents
• Size and packing of constituent elements results
  in regular rigid structure
• Electrical neutrality requires balanced ionic
  charges Stoichiometry

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Bond Types

• Covalent bond
• Only a few minerals
• Results from shared electrons to satisfy octet
  rule
• See diamond

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Bond Types

• Metallic bonding
• A special case of covalent bonding)
• Outer electrons free to move and are shared over
  a wider range in a crystal lattice (long range
  covalent bonding)
• Common in the native elements especially metallic
  minerals
• High electrical conductivity
• High thermal conductivity
• Lustrous
• Ductile

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Bond Types

• Hydrogen bond
• Weak bonds due to asymmetry within a crystal
  structure (or molecule) i.e. Hydrogen bonding of
  polar water molecules
• Van der Waals bond
• Weak forces due to electron mobility and
  temporary polarization of charge
• Determines cleavage directions in soft minerals

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The Origin of Earth Materials, Bonding, the
Coordination Principle, and an Introduction to
the Unit Cell

• Relationship between Minerals and Chemistry
• Crystal Chemistry

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Origin of Earth Elements

• In the universe
• Original H He the big bang
• Nuclear fusion to form heavier elements in stars

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Origin of Earth Elements

• In our solar system
• Remnant heavier elements concentrated in the
  terrestrial (Mercury, Mars, Earth, and Venus)
  planets through
• Sequential planetesimal amalgamation
• Fe-Ni rich core first
• Si rich mantle and crust
• Volatile elements (easily vaporized) last, to
  form the atmosphere

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Origin of Earth Elements

• During Earth formation
• Early molten period
• Density differentiation, cooling, and partial
  solidification
• Goldschmidts classification
• Predictability of elemental distribution
• Siderophile (elements associated with iron)
• Chalcophile (elements associated with sulfur)
• Lithophile (elements associated with silica)
• Atmophile (elements that form a gas)

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Abundance of Elements in the Crust and Mantle
Lithophile Elements

• O, Si, Al, Fe, Ca, Na, K, Mg
• Mantle
• Si, O, Fe, and Mg
• Crust
• Si, Al, Ca, Na, K
• Segregation and concentration of elements through
  various Earth processes
• Partial melting- magma formation
• Surface weathering

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Ionic Radius

• Atomic radii (AR) 1 D (angstrom, 10-10 meters)

• Cationsgt generally smaller AR
• Anionsgt generally larger AR
• Variable dependant on atomic number and
  interaction with other ions

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The Coordination PrincipleGeometry of Atomic
Building Blocks

• In an ionically bonded substance (all minerals
  for our purposes) cations are surrounded by
  anions (or anionic complexes)
• In stable mineral crystals
• The number and arrangement of anions surrounding
  a cation forms a
• Coordination polyhedron

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The Coordination PrincipleGeometry of Atomic
Building Blocks

• Coordination polyhedron
• The size and shape of the coordination polyhedron
  is determined by the relative size (ionic radius)
  of the cation and anion (anion complex) involved
• Radius ratio (cation radius/anion radius)
• This shape is described by the number of anions
  surrounding a cation called the
• Coordination number (C.N.)

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Coordination Polyhedron, Radius Ratio, and
Coordination Number

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The Coordination Principle

• Oxygen (O-2) is the most common anion in
  coordination polyhedron
• Silica tetrahedra (SiO4)-4 with coordination
  number of 4, radius ratio of 0.30.
• It is very important