Earth Science: Chemistry, Minerals, and Rocks Flashcards

Fundamental Atomic Structure and Math

• Abbreviations and Variables

  • Atomic Number (at#): Denoted by the symbol $Z$.
  • Atomic Mass (atm): Denoted by the symbol $A$.
  • Atomic Charge (atch): Denoted by the symbol $C$.

• Foundational Math Formulas

  • Atomic Number ($Z$): Calculated as simply the number of protons ($p$) in the atom ($Z = p$). To find this, you just count the protons.
  • Atomic Mass ($A$): Calculated as the sum of protons ($p$) and neutrons ($n$) ($A = p + n$). Note that electrons ($e$) are omitted from this calculation because they are so tiny they do not count for mass.
  • Atomic Charge ($C$): Calculated as the number of protons minus the number of electrons ($C = p - e$).
    • If protons and electrons are equal in number, the Atomic Charge equals $0$ (Neutral).
    • If there are more protons than electrons ($p > e$), the charge is positive ($+$).
    • If there are more electrons than protons ($e > p$), the charge is negative ($-$).

• Step-by-Step Question Examples

  • Question 1: An atom has $8$ protons, $10$ neutrons, and $8$ electrons. What are its at#, atm, and atch?
    • Step 1: Find at# = Protons = $8$.
    • Step 2: Find atm = Protons + Neutrons = $8 + 10 = 18$.
    • Step 3: Find atch = Protons - Electrons = $8 - 8 = 0$ (Neutral).
    • Final Answer: at# = $8$, atm = $18$, atch = $0$.
  • Question 2: An atom has $11$ protons, $12$ neutrons, and $10$ electrons. (This is a charged ion!).
    • at# = Protons = $11$.
    • atm = $11 + 12 = 23$.
    • atch = $11 - 10 = +1$ (Positive charge).
    • Final Answer: at# = $11$, atm = $23$, atch = $+1$.

Radioactivity and Nuclear Decay

• Definition of Radiation: The emission of energy and sometimes particles by an unstable atom in an attempt to become more stable.

• Atomic Instability: Instability occurs in the nucleus of the atom due to two primary factors:

  • Too many protons: Results in too many positive charges concentrated in one place.
  • Too many neutrons: Neutrons may split on their own.

• Primary Types of Radioactivity

  • Alpha ($\alpha$)
    • Composition: Released as an alpha particle, which is a helium nucleus consisting of $2p + 2n$.
    • Physical Properties: Large in size and slow in speed.
    • Atomic Impact:
      • Change to Protons ($p$): $-2$
      • Change to Neutrons ($n$): $-2$
      • Change to Atomic Mass ($A$): $-4$
  • Beta ($\beta$)
    • Composition: Released as a beta particle, which is a fast electron.
    • Physical Properties: Small in size and fast in speed.
    • Atomic Impact:
      • A neutron turns into a proton.
      • Change to Protons ($p$): $+1$
      • Change to Neutrons ($n$): $-1$
      • Atomic Mass ($A$): Remains the same ($0$ change) because the total count of $p + n$ stays the same ($p+1, n-1$).
      • Change to Atomic Charge ($C$): Becomes more positive ($+1$) because there is one more proton and one fewer electron subtracted ($+1$).
  • Gamma ($\gamma$)
    • Composition: Pure energy released as a wave (gamma ray).
    • Physical Properties: No physical size; travels at the speed of light.
    • Atomic Impact: No change ($0$) to the number of protons or neutrons.

Mineralogy

• Occurrence: Minerals are found throughout the entire planet, other planets, moons, and asteroids.

• The Five Requirements to be a Mineral:

  1. Solid: Cannot be liquid, gas, or plasma.
  2. Naturally-occurring: Must occur in nature (this includes locations like the moon).
  3. Crystalline structure: Must have a basic, repeating internal pattern.
  4. Inorganic: Must not be a living component of an organism.
  5. Specific chemical composition: Cannot change without becoming a different substance (e.g., Halite is always $NaCl$; changing it to $Na_2Cl$ means it is no longer halite).
  • Note: Ice is classified as a mineral.

• Distinguishing Minerals: Industry vs. Science

  • Mining Industry Definition: A mineral is anything extracted from the earth.
  • Geologist Definition: Any naturally occurring inorganic solid that possesses an orderly crystalline structure and a definite chemical composition that allows for some variation.

• Properties for Mineral Identification

  1. Crystal Form or Habit: The specific shape in which a mineral grows.
  2. Color: Often the least reliable property because some minerals come in many colors.
  3. Luster: The way light reflects off the mineral. Even if plastic and glass look similar side-by-side, they can be identified by the way light reflects off their unique textures.
  4. Streak: The color of a mineral when it is crushed or powdered.
  5. Broken Surfaces:
     • Cleavage: A very clean, smooth break.
     • Fracture: Breaks roughly or irregularly.
     • Tenacity: Describes how a mineral responds to stress.
  6. Hardness: Measured on the Mohs scale of hardness ($1$ to $10$). This is a logarithmic scale. One determines hardness by comparing the mineral with something of known hardness.
  7. Density: Calculated as $mass/volume$. This property is constant regardless of size (a piece the size of a car or a finger has the same density).
  8. Special Properties: Includes magnetism, smell, and taste.
  9. Ability to Transmit Light:
     • Opaque: No light is transmitted through the sample.
     • Translucent: Light is transmitted, but a clear image is not visible.
     • Transparent: Both light and a clear image are visible through the sample.

Classification and Mineral Groups

• Rock Definition: Any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet. Rocks are aggregates of several different minerals joined in a way that their individual properties are retained.

• Mineral Groups

  • Economic Minerals: Minerals used extensively in the manufacture of products.
  • Rock-Forming Minerals:
    • Silicate Minerals: Contain Oxygen ($O$) and Silicon ($Si$) atoms. These are the building blocks of rocks.
    • Fundamental Building Block: The Silicon-Oxygen tetrahedron ($SiO_4^{4-}$).
    • Primary Elements in Silicates: Iron ($Fe$), Magnesium ($Mg$), Potassium ($K$), Sodium ($Na$), and Calcium ($Ca$).

• Subcategories of Silicates

  • Light Silicate Minerals: Include the Feldspar group, Quartz, Muscovite, and Clay minerals.
  • Dark Silicate Minerals: Include the Olivine group, Pyroxene group, Biotite, Amphibole group, and Garnet.

• Important Non-Silicate Minerals

  • Carbonates, Halides, Oxides, Sulfides, Sulfates, and Native elements.

Petrology: Igneous, Sedimentary, and Metamorphic Rocks

• Rock Types and Foundations

  • Igneous: Formed directly from the cooling and crystallization of molten rock.
  • Sedimentary: Made from pieces of other things.
  • Metamorphic: Formed through an increase in pressure and heat.

• Igneous Rocks

  • Formed from molten rock: Magma (below the surface) or Lava (above the surface).
  • Textures based on Cooling Rate:
    • Coarse-Grained: Slow cooling (Plutonic). Minerals are large enough to be visible individually; has many visible colors.
    • Fine-Grained: Fast cooling (Volcanic). Minerals are not visible; the rock looks like one solid color.
    • Porphyritic: Indicates two cooling rates (slow then fast). Large crystals (phenocrysts) are surrounded by small crystals (groundmass).
    • Glassy: Very fast cooling (often in the presence of water). Plutonic; all glass (e.g., Obsidian).
    • Vesicular: Very light rock containing bubbles/holes caused by gas (e.g., Scoria, Pumice).
  • Compositions based on Silica ($SiO_2$) Content:
    • Felsic: High silica content; light colors (Gray).
    • Intermediate: Medium silica; medium gray colors.
    • Mafic: Low silica; dark colors (Black or dark Gray).
    • Ultramafic: Very low silica; greenish/green colors.
  • Igneous Classification Table:
    • Note: To identify coarse-grained rocks, imagine mixing their colors to determine the equivalent fine-grained types.

• Sedimentary Rocks

  • Clastic (Detrital): Made from broken pieces of other rocks.
    • Process: Weathering (breaking down rocks) $\rightarrow$ Erosion (transport of sediments) $\rightarrow$ Lithification (Rockfication).
    • Lithification Stages: Compaction (sediments squeezed hard until they fuse) and Cementation (sediments are cemented together).
  • Chemical: Made entirely through chemical processes.
  • Biochemical: Made from the remains of organisms (fossils). Fossilization is the process of transforming organic matter into inorganic matter after an organism dies and its body is preserved.

• Metamorphic Rocks

  • Changed by heat and pressure applied to a Protolith (parent rock).
  • Chemical Composition: Does not change; no elements are added or subtracted. Only the arrangement of atoms changes.
  • Pressure Types:
    1. Confining Pressure: Squeezed evenly from all directions; results in a Granoblastic texture.
    2. Differential Stress: Pressure comes mainly from sides with minor pressure in other directions; result is a Foliation texture (squeezed look).

• The Rock Cycle

  • Cycle Path 1: Igneous $\rightarrow$ Weathering/Erosion/Lithification $\rightarrow$ Sedimentary.
  • Cycle Path 2: Sedimentary $\rightarrow$ Heat/Pressure $\rightarrow$ Metamorphic.
  • Cycle Path 3: Metamorphic $\rightarrow$ Melting/Crystallization $\rightarrow$ Igneous.
  • Note: All rock types can be weathered back into sediments or melted back into magma.", "title": "Earth Science Extensive Study Guide: Atoms, Minerals, and Rocks"}