Chapter 5: Atoms to Minerals

Chapter 5.1

Matter and Atoms

Matter Anything that has mass (amount of material) and volume (amount of space an object takes up) Ordinary matter is composed of elements (a substance that cannot be broken into a simpler substance by ordinary chemical means) 200 years ago, John Dalton stated that “each element is made up of tiny particles, all alike, called atoms” Dalton describes an atom as the smallest part of an element that has all the elements properties.

Structure of an atom In its normal state, a neutral atom as an equal number of electrons and protons Atomic # tells how many protons are in the nucleus and is equal to the # of electrons in the electron cloud The nucleus has 99.9% of the atoms mass Energy levels of electrons represents how many electrons each level can hold 2, 8, 18, 32, 21, 9, and 2

Classifying Atoms Periodic table of elements p. 698 Rows represent the increasing number of protons Vertical columns group these elements that have similar chemical properties Mass #; sum of protons and neutrons

Isotope – an atom with a different # of neutrons Potassium Atomic Number 19 Symbol K Atomic Mass 39.10 amu K has 19 protons (atomic number) 20 neutrons (atomic mass – atomic # [39 – 19]) 19 electrons; always equals the of protons

Bonding of Atoms Most substances on earth are not pure they are compounds – contains atoms of 2 or more elements. For a substance to be stable it likes its last electron level to be filled so they fill it by losing or gaining electrons Covalent Bonds – share electrons

Ionic Bonds – when atoms loose or gain an electron they became charged. Gained; [-] Charge Lost; [+] Charge The opposite charge will then attract Ion – a charged atom A metal looses electrons easily to form positive ions. Therefore they can not join with other metals. Nonmetals gain electrons easily to form negative ions. This makes them want to bond to the positive metals.

Metallic Bonds – The bonds that form between metals cause the electrons to move around all the positive ions.

Compounds and Mixtures Compounds can have properties entirely unlike those of the elements of which it is made. Salt NaCl Sodium and Chlorine are both poisonous to humans when separated Compounds can only be separated by chemical means. Mixtures – elements keep their own properties Salt water – water can be separated by boiling

Sodium Metal + Chlorine Gas Halite (Table Salt) =

Chapter 5.2

Composition and Structure of Minerals

What is a mineral? A mineral must be Naturally occurring Solid Definite chemical composition Orderly arrangement of atoms Inorganic (never alive) Most minerals are compounds Quartz SiO2; Silicon and Oxygen Native elements – minerals with a single element Gold (Au), silver (Ag), copper (Cu), Sulfur (S), diamond (C) Rock – different types of minerals and native elements mixed together

Diamond (C) Silver (Ag) Copper (Cu) Gold (Au) Sulfur (S) Native Elements

How minerals form Many minerals form from molten rock in which the atoms can move freely. Once it begins to cool the ions move closer together to form chemical bonds Many different minerals will form. The composition of the magma will control what type form. The slower the magma cools the larger the grains. Can also form from evaporating water – salt New minerals will form when existing minerals are exposed to more heat and pressure.

Structure of Minerals Crystal Structures The orderly arrangement of atoms in a mineral often seen as the minerals shape Salt p. 98 Crystal is a regular geometrical solid with smooth surfaces called crystal faces. Each mineral has its own crystal form There are six basic shapes p. 99

Silicates – minerals that are compounds including silicon and oxygen They also may contain a metal atom Silica tetrahedron – 4 oxygen surrounding 1 silicon

Crystal Structures and Physical Properties Cleavage – tendency to split along definite planes Hardness – resistance to scratch. Sometimes the same element can have different hardness based on its internal structure Diamond – pure carbon very hard Graphite – pure carbon very soft

Chapter 5.3

Identifying Minerals Mineralogy – study of minerals and their properties

Rock Forming Minerals

Identifying Minerals by Inspection Very rarely are minerals Id. by one property Types of Properties Color – easily observed but, least useful Luster – how a mineral reflects light 2 basic types Metallic Nonmetallic Crystal shape

Streak – color of a powdered mineral Metallic minerals streak is at least as dark as a specimen Nonmetallic – colorless or white Cleavage – minerals splits along flat surfaces

Fracture – breaks in directions other than cleavage planes Conchoidial - shell like fracture Splintery – jagged surface Uneven – rough surface Hardness – resistance to scratch Mesh’s hardness scale 1- 10

Chapter 5.4

Mineral Groups

Major Silicates 90% of the minerals in earth’s crust are silicates Quartz – used in watch movements, prisms, heart lamps, lenses, glass and paints. Crystals are considered semiprecious Feldspars – used aluminum atoms in place of some of the silicon which become balanced by other metals. It is used in glass and ceramics Micas (biotite and muscovite) used as electronic insulators, paints, plastics, rubber and roofing.

Biotite Quartz Feldspar Silicates

Ferromagnesium Silicates Olivine – gem quality is known as peridote Kaolinite – is pure white, a clay compound used in ceramics, paint and fiberglass also known as china clay

Carbonates – negative carbonate ions bonded to positive metal ions which are used construction. Calcite and Dolomite give us rock like limestone and marble.

Oxides – Iron bonded with oxygen of sulfur (sulfide) Hematite – iron oxide used to make steel medicine, cosmetics, plastics and paints

Hematite Iron Oxide Fe O 2 3