Chapter 2: Earth Materials

Elements and Compounds Most fundamental substance into which matter can be separated by chemical means Atom Smallest single particle that keeps element’s distinct chemical properties Protons (+) Neutrons (neutral) Electrons (-) Net atom charge Protons (+) + electrons (-)

Elements and Compounds Atomic number # of protons Atomic mass # of protons + # of neutrons Isotopes Atoms with same atomic # but different mass #

Elements & Compounds Electron (-) Electron “shells” Ion Cation (+) Anion (-)

Compounds, molecules and bonding Combo of atoms from 1 or more elements in specific ratio Molecule Smallest unit with all properties of a specific compound Bond Force that holds together atoms in molecules &/or compounds

Compounds, molecules & bonding Ionic Bonding 1 atom transfers electron to another Gain or lose electrons I.e. = Table salt (sodium chloride or NaCl)

Compounds, molecules and bonding Covalent Bond Electrons from different atoms “pair up” & create bond Share electrons Strongest of chemical bonds

Compounds, molecules and bonding Metallic Bond Electrons shared among several atoms Outer electrons drift between atoms Good conductors of heat & electricity

Compounds, molecules and bonding Van der Waals Bond Attraction between electrically neutral molecules with asymmetrical charge Dipolar molecules Weak bonds I.e. Water

What Is a Mineral? Mineral Naturally formed Solid Inorganic Specific crystal structure Specific chemical composition

Composition of minerals Atomic substitution Elements with similar size & charge can substitute for each other Crystal structure Atoms/molecules arranged into regular patterns Mineraloid Polymorphs Same chemical composition but different crystal structure

Telling minerals apart Luster Quality & intensity of light reflection Metallic Non-metallic Vitreous Resinous Pearly

Telling minerals apart Crystal form Any flat or planar surface that forms during mineral growth Habit Particular mineral’s distinctive shape

Telling minerals apart Hardness Image Common Objects Reference Talc 1 Telling minerals apart 2 Gypsum Fingernail (2.5) Calcite 3 Copper Penny (3.5) Hardness Mineral’s resistance to scratching Mohs scale (1-10) Fluorite 4 Wire Nail (4.5) Apatite 5 Glass (5.5) Feldspar 6 Streak Plate (6.5) Quartz 7 Topaz 8 Corundum 9 Diamond 10

Telling minerals apart Cleavage Mineral breaks in a regular pattern Relates to crystal structure within mineral

Telling minerals apart Color Least reliable Light absorbed by mineral Streak Powdered trace of mineral made by rubbing specimen across unglazed porcelain piece

Telling minerals apart Density Mass / volume Compactness of atoms Other mineral properties Birefringent Double images Effervescence Fizzes in acid Magnetic Attracted to magnet Luminescence or fluorescence UV “glow”

Mineral families & their uses Minerals of Earth’s crust Silicate minerals Minerals contain both silicon & oxygen Silicon-oxygen tetrahedron 1 Si atom bonded to 4 O atoms

Mineral families & resources Other minerals of Earth’s crust Oxides Carbonates Ore deposits Localized concentration that can be extracted profitably

Rocks: A First Look Rock Naturally formed aggregate of minerals & possibly other non-mineral matter Record history of Earth processes Biotite Feldspar Quartz Granite

Rocks: A First Look Igneous Sedimentary Metamorphic Form by cooling & solidification of molten rock Magma Sedimentary Form under conditions of low pressure & low temperature near the surface Metamorphic Altered by exposure to high temperature, high pressure or both