Transcript Chapter 5: Atoms to Minerals

Chapter 5: Atoms to
Minerals
Chapter 5.1
Matter and Atoms
Matter
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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
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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
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Periodic table of elements p. 698
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Rows represent the increasing number of
protons
Vertical columns group these elements that
have similar chemical properties
Mass #; sum of protons and neutrons
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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
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Bonding of Atoms
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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
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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.
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Metallic Bonds – The bonds that form
between metals cause the electrons
to move around all the positive ions.
Compounds and Mixtures
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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
Chapter 5.2
Composition and Structure
of Minerals
What is a mineral?
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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
How minerals form
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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
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Crystal Structures
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The orderly arrangement of atoms in a
mineral often seen as the minerals shape
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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
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Silicates – minerals that are
compounds including silicon and
oxygen
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They also may contain a metal atom
Silica tetrahedron – 4 oxygen surrounding 1
silicon
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Crystal Structures and Physical
Properties
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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
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Chapter 5.3
Identifying Minerals
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Mineralogy – study of minerals and their
properties
Rock Forming Minerals
Identifying Minerals by
Inspection
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Very rarely are minerals Id. by one
property
Types of Properties
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Color – easily observed but, least useful
Luster – how a mineral reflects light
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2 basic types
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Metallic
Nonmetallic
Crystal shape
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Streak – color of a powdered mineral
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Metallic minerals streak is at least as dark as a
specimen
Nonmetallic – colorless or white
Cleavage – minerals splits along flat
surfaces
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Fracture – breaks in directions other
than cleavage planes
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Conchoidial - shell like fracture
Splintery – jagged surface
Uneven – rough surface
Hardness – resistance to scratch
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Mesh’s hardness scale 1- 10
Chapter 5.4
Mineral Groups
Major Silicates
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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.
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Ferromagnesium Silicates
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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)
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Hematite – iron oxide used to make
steel medicine, cosmetics, plastics
and paints