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Earth Materials: Minerals
Today’s Lecture: Chapter 5. Patterns in
Nature: Minerals
1. Minerals: Why care?
2. Atoms, ions &
isotopes of the elements
3. Atomic bonding and
the formation of
chemical compounds
4. Minerals: the
building blocks of rocks
Internal structure in
relationship to physical
properties
5. Introduction to
rocks.
Minerals: Why care?
Raw materials for nearly all of the
manufactured products we use are obtained
from minerals.
Examples:
 Aluminum: Soft drink cans
 Graphite (Carbon): Pencil lead and lubricant
 Copper: Electrical components and wire
 Talc: Baby powder
 Silver, gold, gemstones: Jewelry
 Silicon: Computer chips
Malachite: Ore of copper and a gemstone.
Quartz: Source of silicon used
in making computer chips
Galena: Ore of lead
Gemstones!
Minerals: Why Care?
Other reasons:
 Rocks inform us about geologic hazards,
such as volcanic eruptions, earthquakes etc.,
enabling us to make better decisions about how
we interact with the Earth and use its resources
(e.g. siting and designing buildings).
 Rocks hold important clues for
understanding processes of weathering and
erosion. This information can help us use the
Earth’s resources more effectively (e.g.
extraction of mineral and petroleum resources,
soil conservation, degradation of concrete
structures, etc.).
 Rocks enable us to understand our past &
place our lives in proper evolutionary context.
Understanding Matter…
To understand minerals we need to
understand matter and how it is
organized.
The three states of matter:
 Solid
 Liquid
 Gas
States of Matter
Solids-Atoms and molecules organized into fixed
structures with a defined shape (crystals, glass,
plastics). Atoms move (vibrate) even in a solid! Just
limited in a solid.
Liquids-Fluid mixtures of atoms and molecules
existing as charged atoms or molecules (e.g. “ions”).
Atoms in solutions can form loose associations with
each through transient electronic “bonds”. However,
the liquid lacks a fixed structure, like that seen in
most solids.
Gases-Fluids in which atoms and molecules are in
rapid motion, freely moving about with no fixed
structure. Gases expand to fill the available space.
Bulding blocks of minerals
Atoms, elements
and compounds:
Building blocks of minerals
(See Science Toolbox 5.1, page 112 of text)
•Elements: Different types of atoms that, in their
pure form, cannot be divided into other smaller
units without changing their properties.
•Atom: Smallest division of an element,
that still possesses the chemical properties unique
to the element.
•Compounds: Two or more atoms bonded
together. May be composed of atoms of the same
element, or combinations of several different
elements.
Understanding Matter…
What is an atom?
An atom is made up of:
-A nucleus: Central region of atom where most of
the mass resides. Comprised of protons and neutrons.
-Orbiting electrons: High-speed nearly “massless”
particles of negative charge which orbit the nucleus.
electrons
nucleus
Understanding Matter…
Nucleus contains:
Protons
= Particles with a mass of 1.0 and a
positive electrical charge.
Neutrons = “
“
a mass of 1.0 and a
neutral electrical charge. Neutrons may
be thought of as a proton bound to an
electron.
electrons
A single
atom
protons
Orbiting the
nucleus are
electrons having
essentially no
mass ands a
negative charge.
Understanding Matter…
A simple “ Bohr” model for a single atom:
T&L: Figure 2.4 A
Structure of an Atom
...in reality
Nucleus of protons
and neutrons
T&L: Figure 2.4 B
Types of Atoms and Elements
Number of protons in the
nucleus of an element is called
Its atomic number.
Model of
one atom
nucleus
Elements are distinguished from
each other by their atomic
number.
Examples: All Helium atoms have 2 protons
“ Carbon “
“ Uranium “
“ 6
“ 92
“
“
Isotopes: Same element, different mass
Mass Variations in Elements:
 The number of protons plus the number of neutrons
in the nucleus defines the atomic mass of the element.
However, most elements come in different “species”versions that differ slightly in mass because of having
different numbers of neutrons in the nucleus.
These “species”of elements are called isotopes.
Isotopes: Atoms that vary in the number of neutrons in the nucleus
Again… mass variations of the same element are
called “isotopes”.
Many isotopes are unstable, and disintegrate
through a process called radioactive decay
where particles and/or energy are emitted
from the nucleus
Example: Carbon-14
14
C
is unstable
The rate of radioactive disintegration is constant, so
they can be used as a kind of clock for dating rocks!
Classifying the Elements
Let’s review using Carbon as an example:
Number of protons determines the type of atom
6 protons = carbon
 Number of neutrons in an atom can vary.
 Number of neutrons plus the number of protons equals the
atomic “mass”.
How we write it
Here are the three isotopes of Carbon:
6 protons & 6 neutrons: mass number = 12 12C
6 protons & 7 neutrons: mass number = 13 13C
6 protons & 8 neutrons: mass number = 14 14C
Elements are classified by the number of protons
in the nucleus (I.e., their atomic number)
Periodic table of the elements
equals # of protons
6 => 6 protons
Classifying the Elelemnts
112 known elements
Only 92 occur
naturally
Classifying the Elements
You’ve heard of many of these elements, for example:
Helium
Hydrogen
Oxygen
Aluminum
Iron
Calcium
Titanium
Gold
Ions: Charged Atoms
Atoms that lose or gain electrons develop a charge.
When atoms give away or gain electrons, they
are no longer electrically neutral. In other words,
They take on an electrical charge.
Any atom possessing a charge is called an “ion”.
Atoms with a positive charge are called “cations”.
Those with a negative charge are called “anions”.
Making Minerals
~ 4000 minerals on Earth!
 Different elements combine to make chemical
compounds…
Example 1: water (2 hydrogen atoms + 1 oxygen atom = H2O)
Example 2: salt (1 sodium atom + 1 chlorine atom = NaCl)
Minerals are naturally-occurring compounds that
are classified by their:
 Chemical composition
 Internal (“atomic”) structure
Example: Quartz
Quartz contains:
silicon (Si) and
oxygen (O)
element
name
Chemical formula for quartz is: SiO2
symbol
What are minerals?
Definition of a mineral:
-> To be considered a mineral, it must:
1. Occur naturally
2. Be inorganic
3. Be a solid
4. Possess an orderly internal structure
5. Have a defined chemical composition
Making Compounds
 Atomic Bonding
How do different elements combine to form compounds?
=> By bonding between atoms!
3 main ways:
“Ionic bonding” - loaning electrons
“Covalent bonding” - sharing electrons
“Metallic bonding” - electrons are free to move about from atom to atom
Atomic Bonding
 Ionic Bonding
Example: Table Salt: Sodium (Na) and Chlorine (Cl)
Sodium gives up an
electron becoming
a positively-charged
charged cation.
Chlorine picks up the electron
from Sodium taking becoming
a negatively charged anion.
The atoms bond based on these charge differences.
Ionic Bonding
Example: Sodium (Na) and Chlorine (Cl)
Atoms arrange in orderly fashion: w/ alternating sodium and chlorine
atoms, so each negative ion is surrounded by positive ions, and visa versa.
Crystal Form Reflects Internal Structure
Example: Sodium (Na) and Chlorine (Cl)
Such orderly arrangement at the atomic level produces specific shapes
in crystals at the macroscopic level that reflect the atomic structure
The structure of minerals depends on:
 Size of the ions involved
 Electrical charge of the ions involved
Crystal Form Reflects the Internal Arrangement of Atoms