Atomic Structure and Minerals

Basic Structure of Atoms Smallest particles of matter Have all the characteristics of an element Nucleus – central part of an atom that contains _________ – positive electrical charges _________ – neutral electrical charges

Energy levels, or shells Surround nucleus Contain _________ – negative electrical charges

Atomic Bonding and Isotopes Bonding of atoms Forms a compound with two or more elements Ions are atoms that gain or lose electrons Atomic number is the number of protons in an atom's nucleus _________ Have varying number of _________

Isotopes Have different mass numbers – the sum of the neutrons plus protons Many isotopes are radioactive and emit energy and particles C, O, U, Ar, K, and Pb are some of the most common isotopes used in geologic investigations.

Periodic Table of the elements

Average Abundances for the ____________ Hydrogen is most abundant Helium is second most abundant 04.10.b3

Average Abundances for the ____________ Oxygen second abundant element Magnesium is abundant metal Silicon third most abundant element Iron most (abundant) and nickel in core 04.10.b2 Sulfur abundant in core

Average Abundances in _____________ Oxygen is most abundant element Some abundant metals Silicon is second most abundant; aluminum is third 04.10.b1 Iron is most abundant transition metal

Elements in the Earth’s Crust The eight elements that compose most rock-forming minerals are oxygen (O), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg) Most abundant atoms in Earth's crust are oxygen (46.6% by weight) and silicon (27.7% by weight)

How Atoms Bond Together Sharing Loaning Free flow Stick together Inter- molecular force Metallic bond Covalent bond Ionic bond 04.12.a

How Are Atoms Arranged in a Mineral? 04.04.c1-3 Cubic Tetrahedron Octahedron

Definition of a Mineral _______ _________ Possess an orderly internal structure of atoms Have a ________ chemical composition __________ - lacks an orderly internal structure

Mineraloid Large openings Small openings Openings of different sizes allows the material to flow.

Physical properties of minerals Crystal form Luster Color Streak Hardness Cleavage Fracture Specific gravity Other properties Taste Smell Elasticity Malleability

Crystal Form Generally reflects internal atomic arrangement Typically manifests best when crystals have lots of room to grow.

What Controls a Crystal’s Shape? Internal structure of halite Halite (NaCl) Sizes and packing of atoms 04.04.a

Crystal Lattice Orderly arrangement of atoms Repeating pattern 04.04.b

Crystal Form

Luster Metallic Non-metallic

Color

Streak

Hardness

Bonds with Same Strength Mineral can break along three sets of planes without passing through an atom Mineral breaks through the lattice in nearly any direction so it will fracture 04.05.b

Cleavage

Atomic Scale of Mineral Cleavage Brown atoms bonded with blue atoms into flat sheets (strong bonds) Sheets joined by long bonds between sheets (break along weakest bonds) Cleave into sheets 04.05.a

Fracture

Special Properties Other properties Feel (Talc, Chlorite) Magnetism (Magnetite) Double Refraction (Calcite) Reaction to hydrochloric acid (Calcite)

Building Rocks A few dozen minerals are called the rock-forming minerals These minerals can be grouped according to their elemental makeup.

Mineral Groups _________ Non-silicates ___________ (Limestones) Oxides Sulfides Native Metals– Elements Sulfates

Silicates Composed of _________________ Crystallize from molten material Minerals are divided by how the silica tetrahedra are arranged.

The silicate (SiO4)-4 molecule

Silicate Minerals Silicate tetrahedron Tetrahedra bond together and with other elements 04.07.b

Rock-forming silicates Groups based upon tetrahedral arrangement Olivine – independent tetrahedra Pyroxene group – tetrahedra are arranged in chains Amphibole group – tetrahedra are arranged in double chains

Independent Tetrahedra 04.07.c Olivine Tetrahedra bond to other elements, not other tetrahedra

Single Chains Tetrahedra bond together to form single chains Pyroxene

Double Chains Tetrahedra bond to form double chains 04.07.c Amphibole

Rock-forming silicates Micas – tetrahedra are arranged in sheets Two types of mica are biotite (dark) and muscovite (light) Feldspars - Three-dimensional network of tetrahedra Two types of feldspar are Orthoclase and Plagioclase Feldspars are the most plentiful mineral group Quartz – three-dimensional network of tetrahedra

Sheet Silicates Mica 04.07.c

Frameworks Tetrahedra bonded together and with other elements in 3D framework Quartz Feldspar 04.07.c