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Chapter 5: Atoms to Minerals
Transcript of Chapter 5: Atoms to Minerals
Matter and Atoms
5.2 Composition and Structure of Minerals
5.3. Identifying Minerals
5.4 Mineral Groups
wu: What is the relationship of atoms to matter?
WU: What are minerals and how do they form?
WU: How can minerals be identified?
wu: what are common minerals and how are they classified?
1. Is anything that has mass (amount of material) and volume (amount of space an object takes up)
2. Ordinary matter is composed of elements (a substance that cannot be broken into a simpler substance by ordinary chemical means)
3. 200 years ago, John Dalton stated that “each element is made up of tiny particles, all alike, called atoms”
4. Dalton describes an atom as the smallest part of an element that has all the elements properties.
B.Structure of an Atom
1. In its normal state, a neutral atom has an equal number of electrons and protons.
2. Atomic # tells how many protons are in the nucleus and is equal to the # of electrons in the electron cloud.
3.The nucleus has 99.9% of the atoms mass.
4.Energy levels of electrons represents how many electrons each level can hold 2, 8, 18, 32, 21, 9, 2.
C. Classifying Atoms
1.Periodic table of elements p. 698
increasing number of protons
group these elements have
similar chemical properties
c. Mass number = sum of protons + neutrons
isotope – atoms of the same element with a different # of neutrons
D. Bonding of Atoms
1. Most substances on earth are not pure they are compounds – compounds contain atoms of 2 or more elements.
NaCl, H2O, C6H12O6
2. For a substance to be stable it likes its last electron level to be filled so they fill it by losing or gaining electrons
3.Covalent Bonds – share electrons
4. Ionic Bonds – when atoms lose or gain an electron they became charged.
Gained "- Charge"
Lost "+ Charge"
The opposite charge will then attract
a. Ion – a charged atom
b. A metal loses electrons easily to form positive ions. Therefore they can not join with other metals.
c. Nonmetals gain electrons easily to form negative ions. This makes them want to bond to the positive metals.
5.Metallic Bonds – The bonds that form between metals cause the electrons to move around all the positive ions.
E. Compounds and Mixtures
1. Compounds can have properties entirely unlike those of the elements of which it is made.
e.g. Salt NaCl Sodium and Chlorine are both poisonous to humans when separated
2. Compounds can only be separated by chemical means.
3. Mixtures – elements keep their own properties
e.g. Salt water – water can be separated by boiling
What is a mineral?
1. a mineral must be
a. naturally occurring
c. definite chemical composition
d. orderly arrangement of atoms
e. inorganic (never alive)
2. most minerals are compounds
e.g. quartz => SiO2 Silicon and Oxygen
– minerals with a single element
e.g. gold (Au), silver (Ag), copper (Cu), Sulfur (S), diamond (C)
– different types of minerals & native elements mixed together
(2or more element-minerals & natives mixed)
B. How minerals form
1. Many minerals form from molten rock where the atoms can move freely.
Once it begins to cool the ions move closer together to form chemical bonds
2. Many different minerals will form.
The composition of the magma will control what type form.
3. The slower the magma cools the larger the grains of minerals.
4. Can also form from evaporating water –> like salt.
5. New minerals will form when existing minerals are exposed to more heat and pressure.
C. Structure of Minerals
1. Crystal Structures
a. The orderly arrangement of atoms in a mineral often seen as the minerals shape.
e.g. salt p. 98
b. Crystal is a regular geometrical solid with smooth surfaces called crystal faces.
c. Each mineral has its own crystal form
d. There are six basic shapes p. 99
2. Silicates – minerals that are compounds including silicon and oxygen
a. They also may contain a metal atom
b. Silica tetrahedron – 4 oxygen around 1 silicon
3. Crystal Structures and Physical Properties
a. Cleavage – tendency to split along definite planes
b. Hardness – resistance to scratch. Sometimes the same element can have different hardness based on its internal structure
e.g. diamond – pure carbon very hard
graphite – pure carbon very soft
Mineralogy – study of minerals and their properties
A. Rock Forming Minerals
1. 4,000 known minerals, 30 are common most are rare like gold and diamond.
2. The most common ones make up most of earth’s crystal rocks. quartz, feldspar, mica, and calcite are most common
B.Identifying Minerals by Inspection
1.Very rarely are minerals identified by one property
2.Types of Properties
a.Color – easily observed but, least useful
not reliable (similar)
weathering hides color
b. Luster – how a mineral reflects light
2 basic types-
Metallic – reflect light like polished metal
c. Crystal shape
d. Streak – color of a powdered mineral
i. Metallic minerals streak is at least as dark as a specimen
ii. Nonmetallic – colorless or white
Color in powder form
Rub some against ceramic
e. Cleavage – minerals splits along flat surfaces
f. Fracture – breaks in directions other than cleavage planes
i. Conchoidial - shell like fracture
ii. Splintery – jagged surface
iii. Uneven – rough surface
g. Hardness – resistance to scratch
Moh’s hardness scale 1- 10
B. Non-silicate minerals
(chlorine, fluorine with sodium, potassium or calcium)
(uncombined with other elements)
(oxygen with element other than silicon)
(one or more elements combined with sulfur)
(O) and can also contain 1 or more
They combine in different arrangements.
the ratio of the mass of a substance to its volume
•Fluorescence & phosphorescence
the ability to glow under ultraviolet light
continue to glow after removal of ultraviolet light
produce a double image when viewing an object
- 90% of the minerals in earth’s crust are silicates
** different types of quarts ~ all have formula SiO2 with a silicate tetrahedral `pure is colorless or white, colored varieties include smokey, rose, amethyst
-used in watch movements, prisms, heat lamps, lenses, glass and paints. Crystals are considered semiprecious
2nd most abundant mineral
in the crust
– used aluminum atoms in place of some of the silicon which become balanced by other metals. It is used in glass and ceramics
a. Most abundant mineral
3. Micas (biotite and muscovite) used as electronic insulators, paints, plastics, rubber and roofing.
4. Ferromagnesium Silicates
a. Olivine – gem quality is known as peridote
b. Kaolinite – is pure white, a clay compound used in ceramics, paint and fiberglass also known as china clay
– negative carbonate ions bonded to positive metal ions ---- used
Calcite and Dolomite give us rock like limestone and marble.
– Iron bonded with oxygen of sulfur (sulfide)
1. Hematite – iron oxide used to make steel, medicine, cosmetics, plastics and paints
to find the number of neutrons
e.g. potassium (K is the symbol)
atomic# = 19
atomic mass = 39.10
K has 19 protons (atomic number)
how many neutrons
(atomic mass – atomic #)
electrons always = # of protons
Silicate minerals make up 90+% of Earth’s crust.
(most common – silicate with some metal) and
make up 50%.
– silicate + potassium
– silicate + sodium or calcium or both
– contain iron & magnesium
•Hornblend, olivine, muscovite, biotite